HomeMy WebLinkAbout901351.tiff REPORT
OF A
GEOTECHNICAL INVESTIGATION
FOR
CITY OF LONGMONT ' S
COMPOSTING FACILITY
WELD COUNTY, COLORADO
CAMP, DRESSER & MCKEE INC .
DENVER, COLORADO
PROJECT N0. 1453-L-89
BY
EMPIRE LABORATORIES , INC .
1242 Bramwood P1 . , P.O . Box 1135
Longmont , Colorado
80501
PL0813
901351
TABLE OF CONTENTS
Table of Contents i
Letter of Transmittal
Report 1
Appendix A A-1
Test Boring Location Plan . . .A-2
Key to Borings A-3
Log of Borings A-4
Appendix B B-1
Consolidation Test Results . . .B-2
Summary of Test Results . . . .B-3
Appendix C C-1
i
eXCIS 2.
Empire Laboratories, Inc. CORPORATE OFFICE
P.O.Box 503•(303)484-0359
GEOTECHNICAL ENGINEERING&MATERIALS TESTING 301 No.Howes• Fort Collins,Colorado 80522
April 13 , 1989
Camp, Dresser & McKee Inc.
2300 15th Street, Suite 400
Denver, CO 80202
Attention : Mr. Jose Valazquez
Gentlemen:
We are pleased to submit our Report of a Geotechnical
Investigation for the proposed Composting Facility to be located
on Highway 119 in Weld County, Colorado.
Based upon the findings of our subsurface investigation, it is
our opinion that this site is suitable for the proposed con-
struction, providing the design criteria and recommendations
set forth in this report are met . The accompanying report
presents the results of our subsurface investigation and our
recommendations based on the results .
Very truly yours, •,,,.
„e,., '
EMPIRE LABORATORIES , INC . -� ;
ed,,,,,Ado9.. pci,Edward J �a ;wi 1� a,;. :'
Paas, P.E. _▪ ,� �,.:..,�
Longmont Branch Manager z. ':.:z
Reviewed by:
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5l ER . • S;,.0
• f��,v1STFRF.,f:o,Z.k
Chester C . Smith, P. E. g is day
r.
President _ 2 4808 '� =
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•;.�' ••..fNG 8 tte•p0 X1:5
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,,(1,' O%ORgI se,`.:0; aA
4� Branch Offices
41-1-1
� P.O.Box 16859 P.O.Box 1135 P.O.Box 1744 P.O-Box 5659 lM
Colorado Springs,CO 80935 Longmont,CO 80502 Greeley,CO 80632 Cheyenne, 82003
� .7 (719)597-2116 (303►776 3921 (303)351-0460 (307)632-9224
� 4 Member of Consulting Engineers Council
REPORT
OF A
GEOTECHNICAL INVESTIGATION
SCOPE
This report presents the results of a Geotechnical
Investigation for the proposed composting facility to be located
on Highway 119 in Weld County, Colorado. The investigation •
was carried out by means of test borings and laboratory testing
of samples obtained from these borings .
SITE INVESTIGATION
The field investigation, carried out on March 31 , 1989
consisted of drilling, logging and sampling thirteen ( 13) test
borings . The locations of the test borings are shown on the
Test Boring Location Plan included in Appendix A of this report .
Boring logs prepared from the field logs are also presented in
Appendix A. These logs illustrate the soils encountered, depth
of sampling and elevations of subsurface groundwater at the
time of our investigation.
All borings were advanced with a four-inch diameter, contin-
uous-type, power-flight auger . The test borings were drilled
to depths of ten ( 10) to fifteen ( 15) feet . The drilling opera-
tions were performed under the supervision of a geotechnical
engineer from Empire Laboratories, Inc . , who made a continuous
visual observation of the soils encountered.
ne€
1 47
SITE LOCATION AND DESCRIPTION
This site is located on the south side of Highway 119 in
Weld County, Colorado. More particularly, this site may be
described as a tract of land situated in the Northeast 1/4 of
Section 8, Township 2 North, Range 68 West of the Sixth P .M. ,
Weld County, Colorado.
This site is bordered on the south by the Longmont landfill .
A commercial building exists north of the site . This property
is open, agricultural land which was cultivated at the time of
our investigation. This property slopes moderately downward
toward the north for good positive drainage.
LABORATORY TESTS AND EXAMINATIONS
Laboratory testing and examination were performed on samples
obtained from the test borings in order to determine the physical
characteristics of the soils encountered. Moisture contents ,
dry unit weights, unconfined compressive strengths , water soluble
sulfates, swelling potentials and Atterberg limits were deter-
mined. A summary of the test results is included in Appendix
B of this report . Swell consolidation characteristics were
also determined, and curves showing this data are also included
in Appendix B.
SOIL AND GROUNDWATER CONDITIONS
The soil profile at the site consists of strata of materials
2
arranged in different combinations . In order of increasing
depth, they are as follows :
( 1 ) Topsoil : The site is overlain by a layer of silty topsoil
approximately one ( 1 ) foot thick. The upper four ( 4 ) to
six ( 6) inches of topsoil has been penetrated by root
growth and organic matter and should not be used as back-
fill or foundation bearing.
( 2 ) Sandy Silty Clay: Light brown sandy silty clay underlies
the topsoil and extends to the underlying bedrock at
depths of three ( 3 ) to seven ( 7) feet . This clay stratum
exhibits low bearing characteristics .
( 3) Siltstcne Sandstone Claystone Bedrock: Siltstone sandstone
claystone bedrock exists beneath the clay stratum at
depths of three ( 3) to seven ( 7 ) feet and extends to the
depths explored. This bedrock stratum contains
intermittant layers of siltstone sandstone and claystone.
The upper one ( 1 ) to four (4 ) feet of bedrock is weathered .
The firm bedrock exhibits high bearing characteristics
and the siltstone claystone bedrock exhibits moderate
swell potential .
( 4 ) Groundwater : At the time of our investigation, no free
groundwater was encountered to the depths explored.
Water levels in this area are subject to change due to
seasonal variations and irrigation demands . In addition,
surface water may percolate through the upper subsoils
and become trapped on the relatively impervious bedrock
stratum, forming a perched water condition.
RECOMMENDATIONS AND DISCUSSION
It is our understanding that the proposed composting
facility will consist of a large composting curing building, a
storage building, a mixing building, an operations building
and a surface storm water containment and evaporation area.
We further understand that the area of the composting curing
building will be land balanced by cutting four (4) to five ( 5 )
feet from the southwest corner of the proposed building area and
filling as much as four (4 ) feet in the proposed northeast
corner of the facility. The composting and curing building,
mixing building and storage buildings are to be constructed
with asphalt pavement floor slabs . The operations building will
be constructed with a concrete slab on grade . It is our under-
standing that the proposed detention pond will be four ( 4 ) to
five ( 5) feet deep.
Site Grading
It is recommended that the topsoil containing roots and
organic matter, which extends to a depth of approximately four
( 4) to six ( 6) inches, be removed from the area of the proposed
buildings . This topsoil should be stockpiled for future land-
scaping use . The subgrade should then be scarified to a depth
of six ( 6 ) inches and recompacted two percent ( 2%) above optimum
4 5)(1,05'71,2'l
moisture to ninety percent ( 90%) of Standard Proctor Density
ASTM D 698-78 . (See Appendix C. )
On-site soils or granular soils approved by the geotech-
nical engineer are suitable for use as fill in the proposed
building areas . It is recommended that the siltstone claystone
bedrock not be used as fill in proposed building areas due to
its swell potential . All fill underlying the building areas
should be placed in layers not exceeding eight (8) inches in
thickness and compacted two percent ( 2%) above optimum moisture
to a minimum of ninety-five percent (95%) of Standard Proctor
Density ASTM D 698-78 .
All fill should be inspected by the geotechnical engineer,
and field density tests should be taken under the supervision
of the geotechnical engineer to verify that the specified com-
paction requirements are attained in the field.
The soils in the area of the proposed detention pond are
relatively impermeable to depths of four ( 4 ) to five ( 5 ) feet .
A relatively permeable siltstone sandstone bedrock or sandy
silt exists at depths of four (4 ) to five (5) feet and lower
in the area of the proposed detention pond. Cuts and fills
for the proposed detention ponds should be placed on slopes no
steeper than 3 : 1 . Cut areas in the detention pond founded in
the upper clay soils should be scarified a minimum of eight
( 8) inches and compacted at or near optimum moisture to a minimum
of ninety-five percent (95%) of Standard Proctor Density ASTM
D 698-78 . Where the bottom or sides of the detention ponds
5
SC IC''"9,x.o/z
are founded within the siltstone sandstone or sandy silt , the
pond bottom and sides should be overexcavated a minimum of one
( 1 ) foot . The overexcavated areas should be backfilled with
the on-site clays or imported clay materials approved by the
geotechnical engineer. The clay should be placed in uniform
six ( 6) to eight ( 8) inch lifts and compacted at or wet of
optimum moisture to a minimum of ninety-five percent (95%) of
Standard Proctor Density ASTM D 698-78 . Berms surrounding the
proposed detention pond should be constructed with the on-site
clays or imported clay materials . Embankment fill should be
placed in uniform six ( 6) to eight ( 8) inch lifts and compacted
at or wet of optimum moisture to a minimum of ninety-five percent
( 95%) of Standard Proctor Density ASTM D 698-78 . To minimize
erosion, the slopes and bottom of the detention pond should be
seeded . Pipes or apertures through the detention pond should
be surrounded by a minimum of two ( 2 ) feet of the on-site clay
soil compacted to a minimum of one hundred percent ( 100%) of
Standard Proctor Density ASTM D 698-78 .
Foundations
Based on the swelling potentials of the bedrock at this site
and the magnitude of the loads transmitted by the structures ,
it is our opinion that these structures should be supported by
drilled pier foundation systems . It is recommended that piers
be drilled into the bedrock stratum and that structural grade
beams span the piers . These piers would support the structure
through friction and end bearing. The piers should be straight-
6
L`"� ?,i
shaft and should be drilled with plumb tolerances of one and
one-half percent ( 1 1/2%) relative to the length of the pier .
All piers should have minimum ten ( 10) foot lengths . They
should be drilled a minimum depth of three ( 3) feet into the
firm bedrock stratum and when founded at this level may be
designed for a maximum allowable end bearing pressure of fifteen
thousand ( 15 ,000) pounds per square foot . It is estimated
that a skin friction of one thousand five hundred ( 1 , 500) pounds
per square foot will be developed for that portion of the pier
embedded more than three ( 3) feet into the firm bedrock stratum.
We recommend that piers be designed for a minimum dead load of
five thousand ( 5 , 000) pounds per square foot to counteract
swelling pressures which will develop if the subsoils become
wetted. Skin friction from additional embeddment into the firm
bedrock may be used to resist uplift if necessary. To help
provide the required skin friction, the sides of the pier drilled
into the bedrock stratum should be roughened. All piers should
be reinforced for their full length to resist tensile stress
created by swelling pressures acting on the pier . It is recom-
mended that piers be a minimum of twelve ( 12 ) inches in diameter
to facilitate cleaning, dewatering and inspection. All grade
beams must have a minimum four ( 4 ) inch void between the bottom
of the beam and the underlying soil .
It is strongly recommended that the geotechnical engineer
be present during the drilling operations to: ( 1 ) identify
the firm bedrock stratum, ( 2 ) assure that proper penetation
7 T 0
into sound bedrock is obtained, ( 3) ascertain that all drill
holes are thoroughly cleaned and dewatered prior to placement
of any foundation concrete, ( 4) check all drill holes to assure
that they are plumb and of the proper diameter, and (5) insure
proper placement of concrete and reinforcment.
All excavations should be dug on safe and stable slopes.
It is suggested that excavated slopes be on minimum grades of
1-1/2 : 1 or flatter. The slope of the sides of the excavations
should comply with local codes or OSHA regulations . Where
this is not practical , sheeting, shoring and/or bracing of the
excavation will be required. The sheeting, shoring and bracing
of the excavation should be done to prevent sliding or caving
of the excavation walls and to protect construction workers
and adjacent structures . The side slopes of the excavation or
sheeting, shoring or bracing should be maintained under safe
conditions until completion of the backfilling. In addition,
heavy construction equipment should be kept a safe distance
from the edge of the excavation.
Slabs on Grade
The subgrade beneath slabs on grade should be prepared as
described in the "Site Grading" section of this report . We
recommend that the floor slabs be placed a minimum of three
( 3 ) feet above the bedrock stratum. It is recommended that a
four (4 ) inch layer of clean gravel or crushed rock devoid of
fines be placed beneath floor slabs . This material will help
to distribute the floor loads and will act as a capillary
8 OrGS',!sa
break. It is suggested that all slabs on grade be designed
structurally independent of all bearing members . It should be
noted that the bedrock at this site is expansive, if this
bedrock below slabs on grade becomes wetted, movement of the
slabs on grade may occur .
If building construction is performed during winter months ,
it is recommended that slabs on grade not be placed on frozen
ground and that they be protected from freezing temperatures
until they are properly cured .
All slabs on grade should be designed for the imposed
loading. In order to minimize and control shrinkage cracks
which develop in slabs on grade, it is suggested that control
joints be placed every fifteen ( 15) to twenty ( 20) feet and
that the total area contained within these joints be no greater
than four hundred (400) square feet .
Flexible Floor Slabs & Pavement
It is our understanding that approximately fifteen ( 15 )
single axle dump trucks with five ( 5) to six ( 6) ton loads
will use the drive areas at this site each day. We further
understand that a loader will transport material from the mixing
building into the composting building each day.
Based on the proposed cuts in the area of the composting
and curing building and drive areas the flexible pavement at
this site will be placed on expansive bedrock in some areas .
It is suggested that in areas where the pavement sections are
on or within two ( 2 ) feet of the bedrock stratum that this
9
Cr�, ^a
subgrade be treated with fly ash, kiln dust or lime to reduce
the swell potential of the subgrade soil . It is recommended
that a ten percent mixture of kiln dust or fly ash or a four
percent mixture of lime be disked a minimum of six (6) inches
into the expansive bedrock. The subgrade should then be
recompacted two percent ( 2%) above optimum moisture to a minimum
of ninety percent (90%) of Standard Proctor Density ASTM D
698-78 . The subgrade in all other areas should be scarified
to a depth of six ( 6) inches and recompacted two percent ( 2%)
above optimum moisture to a minimum of ninety percent ( 90%) of
Standard Proctor Density ASTM D 698-78 . Samples of the upper
soils were classified for the purpose of determining pavement
design criteria . The soils tested for Atterberg limits had
group indecies of six ( 6) to nine (9) . Based on these values ,
we recommend the following pavement thicknesses for the proposed
drives , floor slabs and parking areas :
Drives & Areas
Receiving Floor
Truck Traffic Slabs Parking
Asphaltic Concrete 3" 3" 2 1/2"
Select Gravel Base Course 10" 8" 6"
Total Pavement Thickness 13" 11" 8 1/2"
A feasible full depth asphalt alternate would be as follows :
Drives & Areas
Receiving Floor
Truck Traffic Slabs Parking
Asphaltic Concrete Surfacing 2" 2" 2"
Asphaltic Treated Base 4 1/2" 4" 3"
Total Pavement Thickness 6 1/2" 6" 5"
10
6;32 ei I
All topsoil and other unsuitable materials should be
stripped and removed from the proposed paving areas prior to
placing any fill materials or base course. We recommend that
a soil sterilant be used beneath pavement to retard weed growth.
The base course overlying the subgrade should consist of a
hard, durable, crushed rock or stone and filler and should
have a minimum "R" value of 80. The composite base course
material should be free from vegetable matter and lumps or
balls of clay, and should meet Colorado Department of Highway
Class 6 specifications as follows :
Sieve Size % Passing
3/4" 100
#4 30-65
#8 25-55
#200 3-12
Liquid Limit 30 Maximum
Plasticity Index . . . 6 Maximum
The base course and any fill required beneath pavement
areas should be placed at or near optimum moisture and compacted
to at least ninety-five percent ( 95%) of Standard Proctor Density
ASTM D 698-78 . The base course must be shaped to grade so
that proper drainage of the drive areas is obtained.
Dewatering
No free groundwater was encountered at the time of our
investigation, however , a potential perched water table problem
does exist on this site due to the high bedrock stratum.
Therefore , it is recommended that a perimeter drain be
constructed around the proposed buildings which are constructed
11
^-) 7
within three ( 3 ) feet of the bedrock stratum. The dewatering
system should consist of four (4 ) inch diameter perforated pipe,
a sump and pump or other suitable drain outlet . The perforated
pipe should be placed around the entire perimeter of the
buildings. These drains must be placed at least one ( 1 ) foot
below the finished lower level slabs and should have a minimum
grade of one-eighth ( 1/8) inch per foot . Two ( 2 ) inches of
three-quarter ( 3/4) inch crushed rock should extend below the
pipe. This gravel should extend to within one ( 1 ) foot of the
ground surface . It is recommended that building paper or straw
be placed over the gravel to prevent clogging of the gravel
media . Clay backfill should be used over the building paper
to prevent surface water from entering the system. The drains
should flow to a sump or by gravity to a suitable discharge
area. The sump, if used, should be at least three ( 3 ) feet
below the finished floor system and should have at least one
( 1 ) foot of gravel around and below the sump. A pump adequate
to discharge flows should be installed in the sump.
GENERAL RECOMMENDATIONS
( 1 ) Laboratory test results indicated that water soluble
sulfates in the soil are negligble, and a Type I/II cement
may be used in concrete exposed to subsoils . Slabs on
grade subjected to de-icing chemicals should have low
water-cement ratios and higher air contents .
12
( 2 ) Finished grade should be sloped away from the structures
on all sides to give positive drainage. Ten percent
( 10%) for the first ten ( 10) feet away from the structures
is the suggested slope .
( 3) Backfill around the outside perimeter of the structures
should be mechanically compacted at optimum moisture to
at least ninety percent (90%) of Standard Proctor Density
ASTM D 698-78 . (See Appendix C. ) Puddling should not
be permitted as a method of compaction.
(4 ) All plumbing and utility trenches underlying slabs and
paved areas should be backfilled with an approved material
compacted to at least ninety-five percent (95%) of Standard
Proctor Density ASTM D 698-78 . Puddling should not be
permitted as a method of compaction.
( 5) Gutters and downspouts should be designed to carry roof
runoff water well beyond the backfill area.
( 6) Underground sprinkling systems should be designed such
that piping is placed a minimum of five ( 5 ) feet outside
the backfill of the structure, heads should be designed
so that irrigation water is not sprayed onto the found-
ation walls . These recommendations should be taken into
account in the landscape planning .
( 7) Footing sizes should be proportioned to equalize the
unit loads applied to the soil and thus minimize differen-
tial settlements.
13 of ' '
�e 7?•. .
( 8) Plumbing under slabs on grade should be eliminated wherever
possible since plumbing failures are quite frequently
the source of free water which causes slab heave .
( 9 ) It is recommended that all compaction requirements speci-
fied herein be verified in the field with density tests
performed under the supervision of a geotechnical engineer .
( 10) It is recommended that a registered professional engineer
design the substructures and that he take into account
the findings and recommendations of this report .
GENERAL COMMENTS
This report has been prepared to aid in the evaluation of
the property and to assist the architect and/or engineer in
the design of this project . In the event that any changes in
the design of the structures or their locations are planned, the
conclusions and recommendations contained in this report will
not be considered valid unless said changes are reviewed and
conclusions of this report modified or approved in writing by
Empire Laboratories , Inc. , the geotechnical engineer of record .
Every effort was made to provide comprehensive site coverage
through careful locations of the test borings , while keeping the
site investigation economically feasible. Variations in soil
and groundwater conditions between test borings may be encoun-
tered during construction. In order to permit correlation
between the reported subsurface conditions and the actual
14
C1 a
conditions encountered during construction and to aid in carrying
out the plans and specifications as originally contemplated,
it is recommended that Empire Laboratories , Inc . , be retained
to perform continuous review during the excavation and foundation
phases of the work. Empire Laboratories, Inc. assumes no
responsibility for compliance with the recommendations included
in this report unless they have been retained to perform adequate
on-site construction review during the course of construction.
15 :e( 0S2.R
APPENDIX A.
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VC 0' 24
TEST BORING LOCATION PLAN ;
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EMPIRE LABORATORIES, INC.
KEY TO BORING LOGS
e. i TOPSOIL ••; GRAVEL
e i le • . •
Mw FILL SAND& GRAVEL
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/ SILT •i•/ SILTY SAND& GRAVEL
r.1 CLAYEY SILT �op� COBBLES
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.� .� . SAND,GRAVEL&COBBLES -
IMPIIIIIIIIIII
ro CLAY � WEATHERED BEDROCK
1:4 SILTY CLAY __ SILTSTONE BEDROCK
re SANDY CLAY CLAYSTONE BEDROCK
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SAND • • • SANDSTONE BEDROCK
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1 ' SHELBY TUBE SAMPLE
ElSTANDARD PENETRATION DRIVE SAMPLER
WATER TABLE 1 week AFTER DRILLING
C HOLE CAVED '
5/12 Indicates that 5 blows of a 140 pound hammer falling 30 inches was required to penekettp.1 tnchs5 4
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EMPIRE LABORATORIES, INC. r
LOG OF BORINGS
ELEVA-naN No.1 ROZ ►J0..3 PdA-
4920
5/12
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EMPIRE LABORATORIES, INC.
LOG OF BORINGS
_ ELe VAT W Na5 No.& of No.0
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A-5 SC C921
EMPIRE LABORATORIES, INC.
LOG OF BORINGS
�L�v�rioN WO.9 NO.10 Na 11
5/12
4915
20/12
4910
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50/3 -
10/12 J� i
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9/12
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50/7 -i 50/11
4895
50/6
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EMPIRE LABORATORIES, INC.
LOG OF BORINGS
aevAnal4 N0.12 0.13
4910
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EMPIRE LABORATORIES, INC.
APPENDIX B.
CONSOLIDATION--SWELL TEST
- -
BORING NO. 7 DEPTH_ • 0
" pRY bENSiTY 1 1 4. 1 PC F
% MOISTURE 1 1 ' 2%
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APPLIED PRESSURE—TONS/SO. FT.
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B-6
APPENDIX C.
n .0 A
APPENDIX C.
•
Suggested Specifications for Placement of Compacted Earth Fill
and/or Backfills.
GENERAL
A geotechnical engineer shall be on-site to provide continuous observation
during filling and grading operations and shall be the owner's
representative to inspect placement of all compacted fill and/or backfill on
the project. The geotechnical engineer shall approve all earth materials
prior to their use, the methods of placing, and the degree of compaction
obtained.
MATERIALS
Soils used for all compacted fill and backfill shall be approved by the
geotechnical engineer prior to their use. The upper two (2) feet of
compacted earth backfill placed adjacent to exterior foundation walls shall
be an impervious, nonexpansive material. No material, including rock,
having a maximum dimension greater than six (6) inches shall be placed
in any fill. Any fill containing rock should be carefully mixed to avoid
nesting and creation of voids. In no case shall frozen material be used
as a fill and/or backfill material.
PREPARATION OF SUBGRADE
All topsoil, vegetation (including trees and brush) , timber, debris,
rubbish, and other unsuitable material shall be removed to a depth
satisfactory to the geotechnical engineer and disposed of by suitable
means before beginning preparation of the subgrade. The subgrade
surface of the area to be filled shall be scarified a minimum depth of six
(6) inches, moistened as necessary, and compacted in a manner specified
below for the subsequent layers of fill. Fill shall not be placed on frozen
or muddy ground.
C-2 Et 092 it
PLACING FILL
No sod, brush, frozen or thawing material , or other unsuitable material
shall be placed in the fill , and no fill shall be placed during unfavorable
weather conditions. All clods shall be broken into small pieces, and
distribution of material in the fill shall be such as to preclude the
formation of lenses of material differing from the surrounding material .
The materials shall be delivered to and spread on the fill surface in a
manner which will result in a uniformly compacted fill . Each layer
shall be thoroughly blade mixed during spreading to insure uniformity of
material and moisture in each layer. Prior to compacting, each layer
shall have a maximum thickness of eight inches, and its upper surface
shall be approximately horizontal . Each successive 6" to 8" lift of
fill being placed on slopes or hillsides should be benched into the
existing slopes, providing good bond between the fill and existing
ground.
MOISTURE CONTROL
While being compacted, the fill material in each layer shall as nearly
as practical contain the amount of moisture required for optimum compaction
or as specified, and the moisture shall be uniform throughout the fill .
The contractor may be required to add necessary moisture to the fill
material and to uniformly mix the water with the fill material if, in
the opinion of the soils engineer, it is not possible to obtain uniform
moisture content by adding water on the fill surface. If, in the opinion
of the soils engineer, the material proposed for use in the compacted
fill is too wet to permit adequate compaction, it shall be dried in an
acceptable manner prior to placement and compaction.
COMPACTION
When an acceptable, uniform moisture content is obtained, each layer
shall be compacted by a method acceptable to the soils engineer and as
specified in the foregoing report as determined by applicable standards.
Compaction shall be performed by rolling with approved, tamping rollers,
DrON2„1
C-3
pneumatic-tired rollers, three-wheel power rollers, vibratory compactors,
or other approved equipment well-suited to the soil being compacted. If
a sheepfoot roller is used, it shall be provided with cleaner bars
attached in a manner which will prevent the accumulation of material
between the tamper feet. The rollers should be designed so that effective
weight can be increased.
MOISTURE-DENSITY DETERMINATION
Samples of representative fill materials to be placed shall be furnished
•
by the contractor to the soils engineer for determination of maximum
density and optimum moisture or percent of Relative Density for these
materials. Tests for this determination will be made using methods
conforming to requirements of ASTM D 698, ASTM D 1557, or ASTM D 2049.
Copies of the results of these tests will be furnished to the owner, the
project engineer, and the contractor. These test results shall be the
basis of control for all compaction effort.
DENSITY TESTS
The density and moisture content of each layer of compacted fill will be
determined by the soils engineer in accordance with ASTM D 1556, ASTM D
2167, or ASTM D 2922. Any material found not to comply with the minimum
specified density shall be recompacted until the required density is
obtained. Sufficient density tests shall be made and submitted to
support the soils engineer's recommendations. The results of density
tests will also be furnished to the owner, the project engineer, and the
contractor by the soils engineer.
C-4
CITY OF LONGMONT
PRELIMINARY DESIGN REPORT
(Revised)
WASTEWATER SOILDS HANDLING PROJECT
COMPOST FACILITY PHASE
September, 1989
PREPARED BY:
RBD, Inc. CDM Inc.
2900 South College Avenue 2300 15th St. , Ste. 400
Fort Collins, CO 80525 Denver, CO 80202
(303) 226-4955
Job No. 213-005
II
O r,rt')H
i
CITY OF LONGMONT
PRELIMINARY DESIGN REPORT
WASTEWATER SOLIDS HANDLING PROJECT
COMPOST FACILITY PHASE
TABLE OF CONTENTS
SECTION PAGE
1. 0 INTRODUCTION 1-1
2 . 0 COMPOSTING FACILITY 2-1
2 . 1 OPERATING PLAN 2-1
2.2 PROCESS 2-2
2. 3 AERATION SYSTEM 2-2
2 . 4 COMPOSTING/CURING BUILDING 2-7
2 .5 MIXING/STORAGE BUILDINGS 2-7
2 . 6 OPERATIONS BUILDING 2-10
3 . 0 SITE 3-1
3 .1 LOCATION AND LAYOUT 3-1
3 .2 DRAINAGE 3-1
3 . 3 UTILITIES 3-3
4 . 0 PRELIMINARY EQUIPMENT LIST 4-1
4. 1 DUMP TRUCKS 4-1
4. 2 MIXING UNITS 4-1
4 . 3 LOADERS 4-1
5. 0 PRELIMINARY COST OPINION 5-1
6. 0 PRELIMINARY DRAWING LIST 6-1
I
LIST OF FIGURES
Figure No. Page
2 .2-1 Composting Pile Cross-Section 2-3
2 . 2-2 Material Flow Diagram (Previously
Composted Material As Recycle) 2-4
2 . 2-3 Material Flow Diagram
(Woodchip Type Recycle) 2-5
2 .4-1 Composting/Curing Building Plan 2-8
2 .5-1 Mixing/Storage Building Plans 2-9
2 . 6-1 Floor Plan - Operations Building 2-11
2 . 6-2 Front/Side Elevations - Operations
Building 2-12
2 . 6-3 Perspective View - Operations Building 2-13
3 . 1-1 Compost Facility Site Plan 3-2
ii
.�,.(`.CS,2 Po
1. O INTRODUCTION
When completed, Longmont's composting facility will become one
part of the City' s overall sludge treatment and disposal system.
Features and the background for the overall system are described
in the Sludge Utilization Plan prepared earlier. That plan con-
sidered Longmont' s sludge disposal needs through the year 2010.
This "Preliminary Design Report - Revised" for the Compost
Facility Phase sets forth the design basis and criteria followed
in the preparation of drawings for designing and bidding the com-
posting facility. This revised report reflects capital cost
changes which resulted from changing the design criteria regard-
ing the quantity of sludge to be processed. The previous report
was based on processing 8.5 dry tons of sludge per day in 5 days
which required a compost facility capable of processing 11. 9 dry
tons of sludge per compost pile . This report is based on
processing 8 .5 dry tons, five days per week which results in an
8 . 5 dry ton compost pile . This reduction in compost pile
capacity is possible because present sludge production is less
than that which was anticipated in the Facility.
The composting facility is to be constructed adjacent to the ex-
isting City of Longmont landfill. Dewatered, undigested sludge
cake will be tracked to the composting facility where it will be
mixed with previously composted material. The aerated static
pile method of composting will be used. Active composting will
occur for 28 days followed by 30 days of curing. The finish com-
post will be drier, pathogen free, and significantly reduced in
volume when compared to the dewatered sludge cake from the was-
tewater treatment plant. To further the goal of volume
reduction, use of woodchips or other amendment will be used only
during facility start-up when previously composted material is
not available for recycling. This method of composting, was
recently piloted at Longmont by University of Colorado.
The facility will consist of a composting/curing building,
mixing/storage buildings and an operations building. Water will
be provided by the Left Hand Water District. Sewer service will
be provided by the Saint Vrain Sanitation District, with a sewer
line located on the north side of Highway 119 . Power will be
provided by Union Rural Electric Association. Weld County has
building code jurisdiction, but the fire responsibility is with
the City of Longmont due to an agreement with Longmont Fire
Protection District. The composting facility can be permitted by
amending the existing landfill Certificate of Designation (CD) .
1-1
.9C G.521‘5s2
2 . 0 COMPOSTING FACILITY
2 . 1 OPERATING PLAN
The City of Longmont Composting Facility is to compost undigested
sludge cake using the aerated static pile method of composting.
Generally, the operation of this composting facility will be as
follows:
a. Sludge cake will be brought to compost facility in dump
trucks 5 days per week.
b. Dump trucks will empty cake into a sludge transfer
enclosure.
c. Recycle material either from storage or fully cured
material from a curing pile will be brought by bucket
loader to the mixing building and placed directly into
a mixing unit.
d. Sludge will be moved from the transfer enclosure
directly to a mixing unit with a large skidsteer
loader.
e. After mixing sludge cake and recycle together in a
mixing unit, the mixture will be discharged into a
small pile next to the mixing unit.
f. A bucket loader will move mixed material to the com-
posting pile to form the core of new pile.
g. A new compost pile will be constructed for each day
that sludge cake is brought to the composting facility.
h. 24 composting pile spaces will be provided to allow for
a gap of 4 pile spaces between the newly constructed
composting pile and the composting pile just becoming
28 days of age.
i. Construction of composting piles will progress in a
counterclockwise fashion around the composting/curing
building.
j . Bed and cover material for the new compost pile will be
moved by bucket loader from the compost pile which has
just attained the age of 28 days.
k. Material not used for bed or cover of a new compost
pile will be moved by bucket loader to a curing pile.
1. Composting will take place for 28 days under aeration
and result in material having total solids content of
60 percent and meeting PFRP requirements.
m. Each curing pile will hold the material removed from
seven compost piles.
n. Curing will take place for 30 days under aeration and
result in material having a total solids content of 70
percent.
o. After curing, material will be moved by bucket loader
either to a mixing unit for blending with sludge cake
or to the storage pile in the storage building.
p. Storage of finish compost and/or amendment will be in
extended type piles in a storage building located
across from the mixing building.
2-1
O1 C;7 ro
I
2 . 2 PROCESS
Design capacity of the composting facility is 8 . 5 dry tons of
sludge cake, five days per week. Dewatered sludge cake will be
brought to the facility five days each week. A single static
pile containing 8.5 dry tons of sludge cake will be constructed
for each day that sludge cake is brought to the facility.
The composting pile will be constructed in two parts. The center
part, or core, consists of a mixture of new sludge cake and pre-
viously composted material. The second part surrounds the core
and acts as a cover and bedding for the core. Figure 2 .2-1 shows
a cross-section of the composting pile.
Figure 2 . 2-2 is a material flow diagram showing the flow of
material throughout the composting process. The initial charac-
ter of the sludge cake is described as well as the character o£
the compost at various process stages. This diagram represents
steady-state design conditions when previously composted material
is used as recycle. Quality of the sludge cake is described in
the Sludge Utilization Plan. The mix ratio of sludge cake to
recycle is 1. 0 to 0.6 by weight and 1. 0 to 0. 8 by volume.
Should it be necessary to use an amendment like woodchips (such
as at start-up) the capacity of the compost facility can remain
the same because pile heights can be greater. This is because of
the structural support provided by such an amendment which allows
airspace to be maintained inside the pile. In the case of
woodchips, each pile would be 6 feet high and have a 60 degree
starting sideslope. Figure 2 . 2-3 illustrates the flow of
material using woodchips and a woodchip type recycle. Mix ratio
of sludge cake to woodchips to woodchip type recycle is 1. 0 to
0. 4 to 0.4 by weight and 1. 0 to 1. 5 to 0. 5 by volume.
2 . 3 AERATION SYSTEM
To control pile temperature and to maintain aerobic conditions,
composting will be carried out with aerated piles. As an aid to
further drying of composted material, curing will also be done
with aerated piles. Both the composting piles and the curing
piles will have air blown up through them. The finish product
storage piles will not be aerated.
Each composting pile will be aerated using a single blower dedi-
cated to that composting pile . The blower will be sized to
provide a peak aeration demand of 135 cfm per dry ton of sludge
cake when running constantly. Lower airflow demands will be
provided by regulating the run time of the blower. For facility
design conditions, each composting blower will provide 1150 cfm
of air and have 5 horsepower motors.
2-2
;?1tmcn
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5,
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Head on the blowers in terms of standard air will be ap-
proximately as follows:
Headloss through compost 3 . 37 inches of water
Distribution piping headloss 0.25 inches of water
Air header pipe headloss 3 . 22 inches of water
6.84 inches of water
When corrected for temperature (100°F) and altitude (5000 feet) ,
the head on the composting blower is approximately 5. 35 inches o£
water. Air will be distributed along the bottom of each compost
pile with three 6-inch diameter polyethylene pipes. This pipe
will be SDR 13 .5 and orange in color in order to be easy to see
and recover from the composting pile. Sections of pipe will be
held together with flexible pipe clamps. Three rows of 1/4-inch
diameter holes spaced 2-inches apart will run down the top of .
each pipe to distribute air beneath the compost pile.
Control of the composting blowers will be by timers and a tem-
perature feedback system. Two thermocouples will be placed into
each composting pile after it is constructed. At regular
intervals, a PLC will read the temperature at each thermocouple.
This temperature will be compared to a setpoint temperature. If
the thermocouple temperature is above the setpoint temperature,
then the blower will be allowed to run. If the thermocouple tem-
perature is below the setpoint temperature, then the blower will
be held off. However, a timer will be used in the control loop
to prevent the blower from cycling on-off too rapidly and to in-
sure that a minimum amount of air is provided to the composting
pile to maintain aerobic conditions. This temperature feedback
control system will be designed, furnished, and installed by the
City to maintain compatibility with existing control systems.
Each curing pile will be provided with two blowers . Running
together, the blowers serving a curing pile will provide 3 cfm of
air per cubic yard of material in the curing pile. Each curing
blower will provide 520 cfm of air and have a 1 horsepower motor.
Head on each curing blower in terms of standard air will be ap-
proximately as follows:
Headloss through curing material 2 . 25 inches of water
Distribution piping headloss 0. 12 inches of water
Air header pipe headloss 1. 34 inches of water
3 . 71 inches o£ water
When corrected for temperature (100°F) and altitude (5000 ft. ) ,
the head on the curing blower is approximately 2 . 90 inches of
water. Like the composting piles, air will be distributed along
the bottom of each curing pile with four 6-inch diameter, orange
colored polyethylene pipes. Control of the curing pile blowers
will be with timers.
2-6
199 O,) t}
2 .4 COMPOSTING/CURING BUILDING
The composting/curing building will be a rigid frame, prefabri-
cated metal building, approximately 319 ' wide x 230 ' deep x 20 '
minimum inside clear height. Figure 2.4-1 provides a plan layout
of the composting/curing building showing column lines ,pile
layout within the building, and sidewalls. At the base of each
sidewall will be a 2 ' to 3 ' high concrete push wall to protect
the building frame and siding. The main structural members will
be galvanized. Wall panels will be uninsulated, 26 gauge color-
coated galvanized steel . Approximately 6000 square feet of
translucent wall panels will be provided along the north and
south walls of the building.
The roof will incorporate translucent panels , covering ap-
proximately twenty-five percent of the roof area. Light trans-
mittance will be a minimum of 50 percent. The roof panels are to
be 26 gauge color-coated galvanized steel, with provisions for
expansion and contraction.
Along the ridge line of the roof will be 9 upblast type fans for
ventilation. Each fan will move approximately 24,400 cfm o£ air
and have a 5 horsepower motor. With all fans operating, there
will be one air change in the building every ten minutes. Each
fan will be individually operated from an "on-off" switch located
inside the composting/curing building.
Design loads shall be in accordance with the latest edition of
the Uniform Building Code (U.B.C. ) adopted by Weld County. Snow
load design shall be 20 pounds per square foot. Wind loading
shall be in accordance with the U.B.C.
The floor for the composting/curing building will be asphalt.
Thickness of asphalt and base material will be .based on the
recommendation in the geotechnical report for the site.
2 . 5 MIXING/STORAGE BUILDINGS
The mixing building is approximately 80 ' wide x 40 ' deep x 20 '
minimum inside clear height. This building covers the two mixing
units, the sludge transfer enclosure, and two small piles of
mixed material beside each mixing unit. Dump trucks bringing
sludge cake to the compost facility will dump into one end of the
sludge transfer enclosure. A large skidsteer stype loader will
then scoope up the sludge cake and transfer it into a mixing
unit. Both ends of the transfer enclosure can be closed off with
roll-up type doors . Across from the mixing building is the
storage building. This building is approximately 78 ' wide x 50 '
deep x 20 ' minimum inside clear height. Space is provided to
store a minimum of 40 days of finish compost in a pile 10 feet
high as well as some amendment storage space. Heavy equipment
used in the composting process can also be parked in this
building . Figure 2 . 5-1 provides a plan layout of the
mixing/storage buildings.
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buildings are the same as for the composting/curing building.
The floors will also be asphalt. At the base of sidewalls for
the mixing building will be 3 '-6" high concrete pushwalls to
protect the building columns and siding. Storage building will
have 5 ' high concrete walls around three sides.
Around the top of each mixing unit will be a wall baffel with an
air intake duct to aid in controlling odors. A fan will draw air
from above the mixing unit and discharge it through a scrubber
pile located adjacent to the mixing building. Another fan will
draw air from the sludge transfer enclosure and discharge it
through the scrubber pile. This fan will provide one air change
every ten minutes. Fan data is as follows:
Mixer Fan Transfer Enclosure Fan
Airflow Rate 410 acfm 1335 acfm
Head 6. 6 in. H2O 7 . 5 in. H2O
Motor Horsepower 7. 5 HP 7.5 HP
Airflow velocity through the scrubber pile will be approximately
1 foot per minute. The scrubber pile will consist of a mixture
of soil and previously composted material approximately three
feet deep. The surface area of the scrubber pile will be ap-
proximately 1728 square feet . Each fan will be individually
operated from an "on-off" switch located inside the mixing
building.
2 . 6. OPERATIONS BUILDING
The operations building will be a one story pre-engineered metal
building approximately 40 feet by 60 feet (2400 square feet) .
This building will have a combination lunch room/ conference
room, an office, a small bench lab, and mens and womens locker
rooms with showers. A drive through vehicle maintenance area
will be provided. Doors to each service bay will be ap-
proximately 12 ' wide x 14 ' high. Figure 2 . 6-1 provides a floor
plan, Figure 2 . 6-2 provides front and side elevations, and Figure
2 . 6-3 provides a perspective view of the proposed operations
building.
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3 .0 SITE
3 . 1 LOCATION AND LAYOUT
An 11-Acre site contiguous to the existing north boundary line of
the City of Longmont landfill is to be acquired. More
specifically, this site is along the west side of the road back
to the landfill and extends approximately 873 feet north of the
landfills north boundary and approximately 562 feet west from the
northeast corner of the landfill site. The site is in Section 8,
Township 2 North, Range 68 West, Weld County, Colorado. Figure
3 . 1-1 shows the proposed site.
Locating the composting facility off the landfill site was neces-
sary because the geotechnical investigation of the landfill indi-
cated that the facilities would be over more than 40 feet of
landfilled material. The proposed site is presently used to grow
corn but is zoned as a PUD for commercial/light industrial uses.
To be used for a composting facility, the site will first need to
be down-zoned to agriculture use. Next, the landfill ' s existing
"certificate of designation" will need to be amended to include
this new site.
The composting/curing building will be located in the center of
the proposed site. North of the building will be a landscape
buffer and the surface stormwater runoff containment and evapora-
tion area. Vehicle movement north of the building will be mini-
mal and no paved roadways are to be provided on the north side.
Composting operations will principally take place within the
composting/curing building and on the south side . The
mixing, storage, and operations buildings will be located south of
the composting/curing building. As shown by Figure 3 . 1-1, the
area between these buildings is to be paved. Also, the existing
unimproved road back to the landfill will be paved to the compost
facility. The north and west sides of this site have no existing
fence so a new one will be constructed. The existing fences
along the south and east sides will remain. Building setbacks
required in agriculturally zoned areas are as follows:
20-feet from right-of-ways
3-feet minimum from property line or
1-foot for each 3-feet of building height, whichever is
greater.
There is no height limitation for buildings in agriculturally
zoned areas.
3 . 2 DRAINAGE
The proposed site slopes at 2 percent from a high point in the
Southwest corner to a low point in the northeast corner. The St.
Vrain River, located just east of the site is 50 feet lower than
the project site. Floor elevations for the proposed buildings
need only be set high enough to assure proper drainage away from
them as they will be well above the flood waters of the St. Vrain
River.
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Offsite drainage from the west will be diverted to the north of
the site by a swale constructed along the west side of the
project. This swall will be designed to carry as a minimum the
25-year, 1-hour storm (State's present interpretation of Solid
Waste Regulations) .
Onsite drainage which has the potential of being contaminated by
the composting operations will be collected in swales which
divert runoff to a surface stormwater runoff containment and
evaporation area. In particular, runoff from the paved areas of
the site will be collected. Figure 3 . 1-1 shows the proposed
routing for these swales. Drainage from areas of the site which
do not have the potential of being contaminated by the composting
operations will sheet flow to the northeast and down the access
road from highway 119.
The Surface Stormwater Runoff Containment and Evaporation Area is
a flat, shallow grassed area from which there is no stormwater
outlet . Stormwater collecting in this area leaves by
evaporation. The area is to be sized to hold the 100-year, 24-
hour storm. As shown by Figure 3 . 1-1, the containment and
evaporation area is located in the northeast corner of the site.
Stormwater runoff from building roofs will be collected in an un-
derground piping system which will discharge to the St. Vrain
River. This underground piping system which will consist of
reinforced concrete pipe with manholes at pipe connections ,
changes in direction, and other appropriate points. The pipe
will be sized for a 100-year, 24-hour storm in order that the
system does not overflow and overload the containment and
evaporation area. The outfall to the St. Vrain River will be
rip-rap. No other drainage other than roof water runoff will be
carried by this piping system.
Weld County does not have published drainage criteria .
Consequently, the drainage design criteria published by the City
of Longmont will be used as the design basis of this project
(except as noted above) .
3 . 3 UTILITIES
Power for the composting facility will be obtained from the Union
Rivial Electric Association. New service facilities will need to
be extended to the site. The extension of electric service
should be coordinated with Dorothy Ruggles, Dept. Head; Union
Rural Electric Association; P. O. Box 929 ; Brighton, Colorado
80601 (303/659-0551) .
An existing telephone service line to the entrance building of
the landfill runs along the east edge of the access road to the
landfill. A new service line will be needed to the operations
building. For telephone engineering information contact Dennis
Smith, U.S. West, Boulder (303)/441-7161) .
3-3
t
V C8 1
A Public Service gas main is located in the Highway 119 right-of-
way. Extension of a gas service to the compost facility is not
required. Instead a propane tank will be provided for heating
the operations building.
Potable water will need to be obtained from the Left Hand Water
Supply Company, P.O. Box 210, Niwot, Colorado, 80544 (303/652-
2188) . The water company has a 1 1/4-inch water main on the
north side of highway 119. It is believed that a 1-inch service
line was bored under the highway to serve the vacant building
just north of the proposed site. If this is so, then that serv-
ice may also be able to serve the compost facility and a new
crossing of Highway 119 will not be needed. Requirements for
connecting to the Left Hand Water Supply Company system will be
conveyed in response to a "Request For Top Consideration" which
must be submitted by the City of Longmont.
An existing 12-inch PVC Saint Vrain Sanitation District sanitary
sewer is in place to serve the compost facility operations
building, a new 8-inch PVC sanitary sewer will be constructed
down the access road to the landfill to the south side of Highway
119. Because the invert of the existing sanitary sewer is nearly
at the same elevation as the ground surface on the south side of
Highway 119, the new sanitary sewer will need to be constructed
eastward along Highway 119. It is anticipated that the sanitary
sewer will need to parallel highway 119 for approximately 600
feet before a jack and bore crossing of Highway 119 can be made.
The Saint Vrain Sanitation District has requested that the new 8-
inch PVC sanitary sewer be constructed deep enough to allow the
property east of the proposed site to be served. Design of this
new sanitary sewer should be coordinated with Lee Lawson, Dis-
trict Manager, St. Vrain Sanitation District, 600 Kimbark,
Longmont, Colorado (303/776-9570) .
3-4
D1.,. 0 r,tar
4. 0 PRELIMINARY EQUIPMENT LIST
4 . 1 DUMP TRUCKS
f
Dump trucks will be used to haul sludge cake from the City of
Longmont wastewater treatment plant to the composting facility.
These trucks are to be single axle type dump trucks with a 6
cubic yard capacity. Their GVW rating should be between 28 , 000
and 33, 000 pounds. The dump body will be approximately 10 feet
long and fitted with a cover. Trucks will be purchased by the
City through City Fleet Purchase.
4 . 2 MIXING UNITS
Two SSI Model 500 (or equal) mixing units are provided to obtain
a homogeneous blend of sludge cake and recycle material. These
units are manufactured by Sludge Systems, Inc. of Long Lake, MN.
Each unit is to be self contained, complete with 60 HP, 3 phase,
440 volt electric motor driven hydraulic drive, and mounted in a
stationary position. The mixing box shall be equipped with a
means of weighing material as it is placed into the mixing unit.
Mixed material will be discharged from the SSI unit into a small
pile beside the mixer. Because the mixer is one of the key
pieces of equipment in the composting process, and is not avail-
able locally, two units will be provided (one as a backup) to in-
sure uninterrupted performance of the composting facility.
4 . 3 LOADERS
Material is moved around the composting facility by means of a
bucket loader. This will be a Caterpillar 950E Wheel Loader (or
equal) fitted with a 6 cubic yard bucket. To extend the reach of
the loader, an ejector type bucket will be used. Because dried
compost can be dusty, the loader will be fitted with a heated and
air-conditioned cab. Also, since loaders can be rented locally,
only one loader is to be provided as part of the equipment for
this facility.
To move material from the sludge transfer enclosure to a mixing
unit, one Bob-Cat Model 980 (or equal) skidsteer loader will be
provided. This loader will be fitted with a 2 C.Y. bucket.
To aid in clean-up around the compost facility, one Bob-Cat Model
743 (or equal) skidsteer loader will be provided.
4-1
' fa 082,.
5.0 PRELIMINARY COST OPINION
This opinion of probable cost is for the composting facility as
presently envisioned. Economic conditions at the time of
bidding, which cannot be predicted, will impact actual construc-
tion cost.
Land (Including legal fees , appraisal , closing costs ,
easements)
11.0 Acres @ $11, 000/Acre $121, 000
Composting/Curing Buildings
Superstructure $565, 000
Drilled Pier Foundation $295, 000
Pavement (10,385 S.Y. @ $8 .30/S.Y. ) $122 , 000
Electrical $201, 000
$1, 183 , 000
Mixing/Storage Buildings
Superstructure $ 56, 000
Drilled Pier Foundation $104, 000
Blowers/Filter Pile $ 65, 000
Pavement $ 10, 000
Electrical $ 18 , 000
$253, 000
Aeration Equipment
Composting Fans (24 @ $6500) $156, 000
Curing Fans (8 @ $8000) $ 64, 000
Roof Ventilator Fans (9 @ $6000) $ 54 , 000
Controls $100, 000
Aeration Piping $ 75, 000
$449, 000
Sitework
Grading & Drainage Improvements $ 83 , 000
Evaporation Pond $ 15, 000
Seed & Mulch $ 2 , 000
Landscaping $ 15, 000
Paving $138, 000
Access Road Reconstruction $ 78, 000
Fencing $ 5, 000
Weather Station $ 10, 000
Site Electrical $ 20, 000
$366, 000
Equipment
Loader (1 @ $175, 000) $175 , 000
SSI Mixer (2 @ $60,500) $121, 000
Skidsteer - Small (1 @ $18, 000) $ 18, 000
Skidsteer - Large (1 @ $54, 000) $ 54 , 000
$368 , 000
5-1
I
neCt 2/5
Operations Building
Building $103 , 000
Electrical $ 23 , 000
Water System (Incl. Fire Prot. ) $ 23 , 000
Sanitary Sewer $ 83 , 000
Jack & Bore $ 36, 000
Utility Service Connection/Tap Fees $ 12, 000
Furnishings $ 15, 000
$295, 000
Sub-Total $3 , 035, 000
10% Contingency $ 303 , 500
GRAND TOTAL $3 , 338 , 500
The above GRAND TOTAL compares with a composting facility total
of $2,454,480 estimated by the Facilities Plan. However, the
Facilities Plan did not include an operations building with of-
fsite utility extensions and did not consider the purchase of ad-
ditional land or reconstruction of the access road to the
landfill.
5-2
Di Cs 74
•
PLAN OF OPERATION
FOR
CITY OF LONGMONT
SOLIDS HANDLING PROJECT
January, 1990
f
PREPARED BY:
RBD, Inc. CDM, Inc.
2900 South College Ave. 1331 17th St. , Suite 1200
Fort Collins, CO 80525 Denver, Colorado 80202
(303) 226-4955
Job No. 213-006
EPA Project C-08-0532
4'(09-> 4
1
TABLE OF CONTENTS Page No.
I. INTRODUCTION 1
II. SCHEDULE OF ACTIVITIES 3
III . ADMINISTRATION AND STAFFING PLAN 9
A. Organizational Structure 9
B. Staff Requirements and Responsibilities 9
C. Work Schedule 12
D. Staffing Schedule 13
E. Personnel Issues 14
IV. COMMUNICATION 22
V. FACILITY OPERATION AND MAINTENANCE 27
PROGRAM AND MANUAL
A. Operational Strategy And Unit Process Control 27
B. Maintenance Management System 30
C. Emergency Response Plan 32
D. Laboratory Requirements 33
E. Operation And Maintenance (O&M) Manual 34
F. Dynamic Policy And Procedures Manual 37
G. Operation During Construction And Start-up 38
H. Start-up Process Control Testing 41
VI. START-UP TRAINING AND ASSISTANCE SERVICES 42
A. Staff Training Program 42
B. Safety Training Program 45
C. Consulting Engineer Services 46
VII. EXPENSES AND REVENUES 48
A. Salaries 48
B. Operation And Maintenance Costs 48
C. Revenues 49
D. Project Costs 49
E. Funding Sources 49
F. Budget Projection 49
SECTION I
INTRODUCTION
The Plan of Operation is prepared for the City of Longmont ad-
ministration and management personnel to describe the programs
essential to the proper functioning of the Solids Handling
Project. Further, the Plan of Operation provides the groundwork
necessary for the elements of the Solids Handling Project to be
efficiently integrated with the operation of the existing was-
tewater treatment facility.
This Plan of Operation is the first part of a three-part program
which will lead to the successful start=up and operation of the
Solids Handling Project facilities. The other two parts are the
Operation and Maintenance (O&M) Manual and Start-Up Assistance
Services provided by the consulting Engineer and Equipment
Manufacturers . The purpose o£ this three-part program is to
supplement the design and construction aspects o£ the new
facilities with operation and management aspects. Each section
which follows addresses a given area of management responsibility
and provides information concerning management ' s role in fulfill-
ing these responsibilities . Section II is a comprehensive
Schedule of Activities which lists key events, their target dates
for completion (both as a calendar time and as a percent of con-
struction completion) , and designates who is responsible for per-
forming the task represented by the key event. This schedule is
very important since, upon review and approval by the Colorado
Department of Health and the U.S . Environmental Protection Agency .
it becomes a condition of the City' s construction grant from the
Federal government.
The Solids Handling Project provides the sludge handling
facilities recommended by the Solids Management Study prepared by
Black and Veatch, 1987 and as further detailed by the Preliminary
Design Report prepared by CDM and RBD in December 1988 and up-
dated in September 1989 . In particular, this project provides a
new gravity thickner and associated pumping facilities and a belt
filter press facility with chemical feed systems and related
sludge handling equipment at the existing wastewater treatment
plant. Also, a new aerated static pile composting facility is
being constructed adjacent to the City ' s existing landfill.
1 °Win%
Two construction contracts are to be awarded to build the
facilities of the Solids Handling Project. One project titled
"In-plant Improvements" deals with work at the existing treatment
facility. The other project titled "Compost Facility" deals with
the construction of the new compost facility. Each contract has
a seperate set of project specifications and construction
drawings. The following is an anticipated project schedule for
administering each of these contracts:
Anticipated Date
Project In Plant Compost
Task Improvements Facility
Receive Bids Jan. 30, 1990 Jan. 17 , 1990
Issue Notice of Award Feb. 27 , 1990 Mar. 12 , 1990
Receive Executed Contract
Documents from Contractor Mar. 13 , 1990 Mar. 26, 1990
Issue Notice to Proceed Mar. 14, 1990 Mar. 27 , 1990
Preconstruction Conference Mar. 19, 1990 Mar. 30, 1990
Contractor Schedules Due Mar. 30, 1990 Apr. 11, 1990
Substantial Completion Dec. 9, 1990 Dec. 25, 1990
Final Completion Feb. 7, 1991 Feb. 23 , 1991
End of One-Year
Correction Period Dec. 9, 1991 Dec. 25, 1991
2
SECTION II
SCHEDULE OF ACTIVITIES
Responsible Section
Key Event Party Reference
Jan. , 1990
Jan. 15 - Begin process to formally
create solids handling group City III-B
Jan. 17 - Receive Compost Bids City Proj . Specs.
Jan. 30 - Receive In-plant Bids City Proj . Specs.
Jan. 30 - Construction Phase
Engineering Services Begin Engineer VI-C
Jan. 31 - Submit Final Plan of Oper-
ation to State for Review State/EPA I
Feb. , 1990
Feb. 12 - Assign/Hire Solids Handling
Operations Supervisor (SHOS) City III-D
Feb. 15 - Begin Development of Staff
Training Program SHOS VI-A
Feb. 15 - Begin Development of Safety
Training Program SHOS VI-B
Feb. 15 - Begin Development of
Emergency Response Plan SHOS V-C
Feb. 15 - Begin Development of Main-
tenance Management System SHOS V-B
Feb. 27 - Issue In-Plant Notice of
Award City Proj . Specs.
March, 1990 (0% Completion of Construction)
Mar. 1 - Final Plan of Operation
Approval State/EPA I
Mar. 12- Issue Compost Notice of
Award City Proj . Spec
Mar. 13 - Receive Executed Contract
Documents From In-Plant
Contractor In-Plant Project
Contractor Specs
Mar. 14 - Issue In-Plant Notice
To Proceed City Proj . Spec
Mar. 14 - Assign/Hire Resident Engineer Engineer VI-C
Mar. 19 - In-Plant Preconstruction
Conference Engineer Proj . Spec
Mar. 26- Receive Executed Contract
Documents From Compost
Contractor Compost Proj . Spec
Contractor
Mar. 27- Issue Compost Notice to
Proceed City Proj . Spec
Mar. 30- Compost Preconstruction
Conference Engineer Proj . Spec
Mar. 30 - In-Plant Contractor
Schedules Due In-Plant
Contractor Proj . Spec
3 'un'4),00
w _z
April, 1990
April 2 - Begin O&M manual preparation Engineer V-E
April 11- Compost Contractor Schedules
Due Compost
Contractor Proj . Spec
May, 1990
May 25 - Draft O&M Manual Materials
Due from Contractors In-Plant & V-E
Compost
Contractors
June, 1990
Jun. 1 - Begin to investigate use of
new City maintenance
management system. SHOS V-B
Jun. 15 - Submit Draft O&M Manual Doc-
uments to State for review Engineer V-E
Jun. 15 - Submit Draft of Emergency
Response Plan to State for
review. SHOS V-C
Jun. 15 - Submit Draft of
Safety Training Program to
State for review. SHOS VI-B
Jun. 15 - Submit Draft Plan for
Maintenance Management System
to State for review. SHOS V-B
Jun. 15 - Submit Draft Plan for Staff
Training Program to State
f for review. SHOS VI-A
July, 1990 (50& Completion of Construction)
July 2 - Receive State Approval of
Drafts state .
July 2 - Begin Developing Maintenance
Management System Forms SHOS V-B
July 16 - City Purchase Compost Fac-
ility Computer Control
Equipment. City V-G
August, 1990
Aug. 1 - Begin Development of Main-
tenance Schedule Sheets SHOS V-B
Aug. 20 - City Begin Programming
Compost Control Computer. City V-G
September, 1990
Sept. 1 - Prepare Draft Dynamic Policy
& Procedures Manual SHOS V-F
Sept. 14- Final O&M Manual Materials
Due from Contractors In-Plant V-E
& Compost
Contractors
Sept. 17- Begin Assigning/Hiring
Solids Handling Group
Operators City III-B
Sept. 17- Begin Work to identiy and
obtain all necessary safety
material and equipment SHOS VI-B
Sept.21 - Detailed Belt Press Testing
Procedure due from Contractor In-Plant
Contractor V-H
October, 1990
Oct. 1 - Complete Emergency Response
Plan SHOS V-C
Oct. 1 - Complete Maintenance Management
forms and Schedule Sheets SHOS V-B
Oct. 1 - Begin Start-Up And Operations
Phase Engineering Services Engineer VI-C
Oct. 5 - Approve Belt Press test
procedure Engineer/SHOS V-H
Oct. 8 - Arrange for polymer for
belt press testing SHOS V-H
Oct. 10 - Arrange with Longmont
Laboratory for belt
press testing SHOS V-H
Oct. 15 - Submit Final O&M Manual
Documents to State for
Review Engineer V-E
Oct. 15- Submit Final Plan for
Staff Training Program to
State for Review SHOS VI-A
Oct. 15 - Submit Final Safety
Training Program to State
for Review SHOS VI-B
Oct. 15 - Submit Final Plan for
Maintenance Management System
to State for Review SHOS V-B
Oct. 22 - Fill Solids Handling Group
Operator Positions City III-D
Oct. 22 - Begin Assigning/Hiring Solids
Handling Group Mechanic City III-B
Oct. 23 - Dewatering Fundamentals
Workshop Engineer/SHOE VI-A
Oct. 24- Begin Equipment Training
by Factory Representatives In-Plant Proj . Spec
Contractor
Oct. 31 - Complete Identification and
Stocking of In-Plant Safety
Supplies SHOS VI-B
November, 1990 (80% Completion of Construction)
Nov. 1 - Arrange for Composting
Start-up Amendment SHOS 7-G
Nov. 1 - Fill Solids Handling Group
Mechanic Position City III-D
Nov. 2 - Group Organization Workshop Engineer/SHC- VI-A
Nov. 5 - City Purchase Dump Truck City V-G
5
d'C <, .
Nov. 7 - Begin 30 Day Performance
Testing of Belt Filter
Presses In-Plant
Contractor V-H
Nov. 15 - Final O&M Manual Approval State/EPA V-E
December, 1990 (90% Completion of Construction)
Dec. 3 - Begin Equipment Training By
Factory Representatives Compost Proj . Spec
Contractor
Dec. 3 - Deliver small load of start-up
amendment to compost facility
for equipment testing City V-G
Dec. 7 - Complete 30 Day Performance
Test of Belt Filter Press In-Plant V-H
Contractor
Dec. 9 - In-Plant Work Substantial
Completion In-Plant Proj . Spec
Contractor
Dec. 10 - Solids Handling Group
Operators Tour Similar
Compost Facilities Engineer/SHOS VI-A
Dec. 17 - Loader & Skid-Steer
deliveries Compost Proj . Spec
Contractor
Dec. 25 - Compost Work Substantial
Completion Compost Proj . Spec
Contractor
Dec. 26 - Purchase compost facility
small tools, lab equipment,
and Operations Building
Furnishings. SHOS V-G
Dec. 31 - City Landfill Closes City V-G
January, 1991
Jan. 2 - Implement Maintenance Man-
agement Program at In-Plant
Facilities SHOS V-B
Jan. 2 - Conduct Tour of In-Plant
Facilities with Police and
Fire Department Personnel SHOS V-C
Jan. 2 - Conduct Tour of In-Plant
Facilities with City Risk
Manager SHOS VI-B
Jan. 4 - Receive Record Drawing
Materials from Contractors In-Plat_ & Proj . Spec
Compose, Contr.
Jan. 4 - Complete identification and
stocking of compost facility
safety supplies. SHOS VI-B
Jan. 7 - Implement maintenance
management program at Compost
Facility. SHOS V-B
Jan. 7 - Begin Installing Compost
Control Computer City V-G
Jan. 10- Conduct Tour of Compost
Facilities with Police and
6a
Fire Dept. Personnel. SHOS V-C
Jan. 11- Conduct Tour of Compost
Facility with City Risk
Manager SHOS VI-B
Jan. 18 - Provide Record Drawings
to City Engineer VI-C
Jan. 21- Health & Safety Workshop Engineer/SHOS VI-A
February, 1991 (100% Completion of Construction)
Feb. 1 - Composing Fundamental
Workshop Engineer/SHOS VI-A
Feb. 1 - Deliver Start-up Amendment
to Compost Facility SHOS V-G
Feb. 7 - In-Plant Work Final
Completion In-Plant Proj . Spec
Contractor
Feb. 11- Begin Practicing Compost
Techniques SHOS VI-A
Feb. 23- Compost Control Computer
Operational City V-G
Feb. 23 - Compost Work Final Completion Compost
Contractor Proj . Spec
March, 1991
March 1 - Implement Safety Training
Program for Solids Handling
Group SHOS VI-B
March 1 - Emergency Operational
Procedures Workshop Engineer/SHOS VI-A
i March 4 - Begin Composting SHOS V-G
April, 1991
April 1 - Finalize Dynamic Policy
& Procedures Manual SHOS V-F
September, 1991
Sept. 15- Begin one-year Review of O&M
Manual Documents Engineer V-E
October, 1991
Oct. 15 - Update O&M Manual Documents
Based on First Year Oper-
ating Experience. Engineer V-E
Oct. 15 - Update Dynamic Policy and
Procedures Manual. SHOS V-F
November, 1991
Nov. 19 - Begin One-Year Performance
Certification Review of
In-Plant Work. Engineer VI-C
5,-)r of C2.43>
December, 1991
Dec. 1 - Begin One-Year Performance
Certification Review of
Compost Work Engineer VI-C
Dec. 9 - Provide In-Plant One-Year
Performance Certification Engineer VI-C
Dec. 24- Provide Compost One-Year
Performance Certification Engineer VI-C
Note: % construction completion based upon amount paid to
Contractor.
SHOS - Solids Handling Operations Supervisor
n r,
8
R.,kj
SECTION III
ADMINISTRATION AND STAFFING PLAN
A. Organizational Structure
A diagram of the existing organizational structure for the City
of Longmont is provided by Figure III-1. The solids handling
project facilities are to be staffed by a Solids Handling Group
which will be created from already existing positions at the
treatment plant. In particular, the Solids Handling Group will
be responsible for Operation and Maintenance of the belt filter
press, the composting facility, and overseeing the existing con-
tract hauling of solids for land application. Figure III-2 is an
organizational diagram showing how the Solids Handling Group fits
into the wastewater treatment plant's organizational structure.
B. Staff Requirements and Responsibilities
The existing wastewater treatment plant is presently disposing of
solids created by the wastewater treatment process through con-
tracting with private haulers for land application. As a result
of implementation of this Solids Handling Project, other methods
will be available to handle and dispose of these solids. More op-
tions will allow for a more reliable, efficient, and easier
method to manage solids handling. It will not result in in-
creased staffing requirements . Instead, the Solids Handling
Group identified in figure I1I-2 will be created by redefining
existing positions at the wastewater plant as solids handling
j group positions. The position of Solids Handling Operator Super-
visor (SHOS) will be created by eliminating an Operator position.
This transfer of personnel can be summarized as follows:
Staff Current Proposed Number
Position Number Plant Solids Handling Group
Operations
Supervisor 1 1 -
Solids Handling
Operations
Supervisor 0 - 1
Operators 11 6 4
Mechanics 7 6 1
Total
Positions 19 13 6
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WATER QUALITY WATER
r LABORATORY OUAUTY -
SUPERVISOR DIRECTOR
TREATMENT PLANT I
OPERATIONS
MANAGER
OPERATIONS MAINTENANCE AMINISTRATIVE
SUPERVISOR SUPERVISOR AIDE
i
SOURS HANDUNG I PLANT OPERATORS I PLANT ADMINISTRATIVE
MECHANICS I CLERK
OPERATIONS SUPERVISOR
SOURS HANDUNG SOLIDS HANDLING GROUP
OPERATORS
SOUDS HANDUNG •
MECHANIC
FORMAL COMMUNICATION
OPERATIONAL COMMUNICATION
WASTEWATER TREATMENT PLANT AND
SOLIDS HANDLING ORGANIZATION
FIGURE III-2
I Z ti. n/� RBD,INC
�,cfel
A statement of responsibilities and qualifications for each posi-
tion identified as part of the Solids Handling Group is included
at the end of this section.
C. Work Schedule
It is anticipated that all Solids Handling Group employees will
work from 7 : 00 a .m. to 3 : 30 p.m. , Monday through Friday
inclusive. The time between 11: 30 and noon will be for lunch.
The added thickner will allow for sludge storage on holidays,
weekends, and during times of mechanical breakdown. Because was-
tewater solids handling processes are generally of a "batch"
nature, working in shifts is not warranted because sludge storage
facilities will be available. When the Solids Handling Group is
not on duty, the dewatering equipment at the treatment plant is
shut off, heavy equipment is safely parked, and the composting
process is being monitored with a computer. A telephone alarm
system is provided for emergency conditions such as fire but the
composting process proceeds at a slow enough pace that process
control can be easily accomplished within the above work hours.
In the future, when sludge production increases, a six or seven
day solids handling operation may be utilized. This is also an
option for peak sludge production times such as in April and May
when sloughing of the trickling filter biofilm occurs.
Typical daily activities of the Solids Handling Group would be as
follows:
Solids Handling
Operations Supervisor - Planning, management, and
analysis of solids handling
needs and performance.
Operator Position 1 - Operate filter press at
treatment plant.
Operator Position 2 - Operate truck to carry dewatered
sludge cake between treatment
plant and composting facility.
Assist at treatment plant and
compost facility.
Operator Position 3 - Operate mixer at compost
facility.
Operator Position 4 - Operate loader at compost
facility to load mixer, carry
newly mixed material to compost
pile, carry previously composted
material to curing pile , and
other material movement
operations.
t s-Cl?yo-
12
Mechanic - Repair solids handling equipment
and perform preventive main-
tenance tasks.
Because solids handling operations are a "batch" type operation,
time-off for holidays is not a problem. The division of work
noted above has sufficient slack that normal time-off for
vacations, training, or sickness can be accommodated. The solids
handling operations supervisor will need to coordinate the
scheduling of vacation and training time to equitably disperse
the added work load among the operators. In addition, the solids
handling operations supervisor can fill in during times of unex-
pected sickness of an operator. Existing plant mechanics can
fill in when the solids handling mechanic is absent. Likewise,
the solids handling mechanic can aid the plant mechanics in their
work to cover for an absent plant mechanic.
D. Staffing Schedule
The Solids handling Group will need to be formed before comple-
tion of construction. In particular, the Solids Handling Opera-
tions Supervisor (SHOS) should be assigned shortly after the
start of construction. The solids handling operators are needed
approximately 50 days prior to substantial completion of the in-
plant work. The solids handling mechanic is needed approximately
40 days prior to in-plant work substantial completion . This
schedule will allow these individuals to become well acquainted
with the equipment and systems they will be expected to operate
upon completion of construction.
f
During construction, the Solids Handling Operations Supervisor
(SHOS) will be needed to aid the Contractor during appropriate
stages of construction . He will also be the primary party
responsible for developing a Staff Training Program, Safety
Training Program, Emergency Response Plan , and Maintenance
Management System. The City has developed a "Dynamic Policy &
Procedures Manual" which they use at their other treatment
facilities to guide plant operators in the day to day operations
of various unit processess and operations . Preparation of a
draft manual of this sort will be a responsiblity of the SHOS.
He will also assist the Engineer in preparing O&M Manuals for the
new facilities. As construction nears completion, the SHOS will
be responsible for aquiring City purchased safety material and
equipment; coordinating City responsibilities for belt filter
press testing; aquisition of composting amendment material , small
tools, lab equipment, and operations building furnishings ; and
finally conducting facility tours with the City Risk Manager and
with police and fire department personnel .
Solids handling group operators must be available to run the belt
filter press equipment for the In-Plant Contractor' s 30 day per-
formance test. Just prior to the start of the performance test,
the Solids Handling Group operators will need to attend workshops
on the Solids Handling Group organization and dewatering
fundamentals. Also, Factory Representatives for fn-Plant equip-
ment will begin their training sessions just prior to the start
of the performance test. After the belt press performance test,
there will be a brief time-period in which the operators can
13 (a f
,12/1
train to prepare for start-up of the composting facility.
The solids handling group mechanic must be available by the start
of the 30 day belt filter press performance test. If possible,
the mechanic should also be available to attend the in-plant
training sessions presented by Factory Representatives.
As outlined in part B of this Section, new staff positions are
not being created. Instead, already existing staff positions are
being redefined to create a solids handling group. Consequently,
the filling of solids handling group staff positions does not
necessarily mean that new personnel will need to be hired. The
following is a schedule for filling the solids handling group
staff positions either by formally assigning existing personnel
to the group or hiring personnel to fill a vacancy:
January 15, 1990
Begin process to formally create
Solids Handling Group
February 12 , 1990
Assign/Hire Solids Handling
Operations Supervisor (SHOS)
September 17, 1990
Begin Assigning/Hiring Solids Handling Group Operator' s
October 22 , 1990
Fill Solids Handling Group Operator Positions
Begin Assigning/Hiring
Solids Handling Group Mechanic
November 1, 1990
( Fill Solids Handling Group Mechanic Position j
E. Personnel Issues
Personnel rules for all employees of the City of Longmont
are contained in the City Code of Longmont, Title 1, Chapter
22 . All new staff positions or vacancies are advertised and
posted by the city Personnel Department. Major personnel
disputes and grievances are also handled by the Personnel
Department. Minor complaints or staff problems are first
directed to the appropriate supervisor for resolution. Dis-
putes only go to the Personnel Department if an "in-house"
solution cannot be reached.
SOLIDS HANDLING GROUP
STATEMENTS OF PERSONNEL DUTIES AND QUALIFICATIONS
15
SOLIDS HANDLING OPERATIONS SUPERVISOR
DESCRIPTION OF WORK
i
Assigns, supervises and reviews the work of the solids handling
staff of the City of Longmont wastewater treatment plant .
Analyzes and reports on solids handling procedures, including
dewatering, digestion, land application and composting. Assures
that solids handling functions are performed in accordance with
local, State and Federal requirements. Administers contracts for
hauling and land applying sludge. Oversees monitoring programs
for sludge, soil and crops. Works under the direction of Was-
tewater Plant Operations Supervisor and coordinates solids han-
dling functions with Laboratory Supervisor, Wastewater Main-
tenance Supervisor, Water Quality engineering and Water Quality
Director.
SUPERVISION RECEIVED AND EXERCISED
Under the overall direction o£ the Operations Supervisor of the
wastewater treatment plant, this position is responsible for the
direct supervision o£ solids handling operations and maintenance
personnel. Other responsibilities include: Managing daily opera-
tion of sludge dewatering and aerated static pile compost
facilities, daily administration of contracts with sludge haulers
for land application and planning and supervising compliance
monitoring for process operation, sludge quality and sludge
disposal.
EXAMPLES OF DUTIES
Duties may include, but are not limited to, the following: As-
- 'r the development and implementation of goals, objectives,
and procedures related to solids handling ; assign
and supervise employees in the operation of solids har-
d _ '_ities ; maintain surveillance of the operating ef-
fi:. _ = sludge dewatering and composting; supervise, train
and e: ,._ -s subordinates; maintain records and prepare reports
regarding operation of sludge dewatering and composting and
the quality of finished/disposed sludges or compost ; suggest
methods of improving solids handling and disposal efficiency;
coordinate the collection of samples from land application sit -s;
coordinate solids monitoring and testing activities with the
Longmont Water Quality Laboratory; coordinate solids handling
functions with wastewater plant maintenance personnel to assure
proper and efficient operation of solids handling equipment and
quality control systems ; coordinate operational changes and ex-
periments with Operations Supervisor and Water Quality engineer-
ing personnel ; oversee the production and utilization of finished
compost; order supplies and materials as needed for proper opera-
tion of solids handling operations; prepare O&M cost estimates;
assist in development of replacement equipment specifications;
assist in -budget preparation and administration; respond to emer-
gencies on an on-call basis 24 hours per day, seven days per
week; respond to citizen inquiries, foster good public relations
and respond to complaints; make critical decisions to resolve
emergency conditions resulting from solids handling system mal-
functions or adverse weather conditions ; keep informed of currant
and proposed regulatory requirements for the treatment and dis-
posal of wastewater solids and keep wastewater plant Operations
Supervisor informed of the possible effects of such requirements
on future plant operations ; perform other duties related to
operation and management of solids handling as assigned.
OUALIFICATIONS
Knowledge of: Operation and maintenance of wastewater treatment
plant solids handling equipment, including composting equipment;
sewage and sludge treatment processes and chemical and bac-
teriological characterisitics and sewer and sludge ; standard
methods of sampling and analyzing wastewater and sludge; standard
methods o£ sampling and analyzing wastewater and sludge ;
automated equipment associated with atment and solids handling
operations; basic hydraulics, incl i flow and volume measuring
devices; pumps, mixers, blowers, s other equipment related to
wastewater and wastewater soli_ , handling; basic engineering
principles and practices as they relate to wastewater treatment
and solids handling; occupational hazards and standard safety
practices and precautions involved in wastewater treatment and
solids handling operations ; principles and practices of
supervision, training and performance evaluation.
Ability to: Plan, schedule and assign work in wastewater solids
handling operation and maintenance; supervise, train and evaluate
subordinates ; prepare and monitor operating budget ; prepare
reports and maintain records; communicate clearly and concisely,
both orally and in writing; use personal computer and standard
/ software to track and monitor solids handling operations ; work
wit tory, Engineering, and other departments of Water
4' Sion to achieve efficient and effective solids han-
_._ation.
NCE OF QUALIFICATIONS
Any combination of education and experience that would provide
the required knowledge and abilities is qualifying, subject to
the following minimum requirements:
Experience: Four years of experience in the operation and main-
tenance of a wastewater treatment plant , with an emphasis on
solids handling and disposal, including supervisory experience or
experience in working with State and Federal regulatory require-
ments for solids handling or wastewater treatment.
Education: Equivalent to the completion of the twelfth grade
supplemented by college-level academic course work in chemistry
or biology and specialized training in wastewater solids treat-
ment and disposal .
License or Certificate : Possession of a Class A Wastewater
Treatment_ Plant Operator' s Certificate issued by the State of
Colorado and possession of a valid Colorado Driver' s License.
17 nr
�r:. 'q
QUALIFICATIONS
Knowledge of: Operation and maintenance of wastewater treatment
plant solids handling equipment; sewage and sludge treatment
processes and chemical and bacteriological characteristics of
sewage sludge; standard methods of sampling and analyzing was-
tewater and sludge; the properties of the chemical compounds,
scientific principles, and the laboratory procedures used in was-
tewater treatment; operational and safety regulations pertaining
to wastewater treatment Solids handling operations ; standard
principles of hydraulics; and principles of personnel management.
Ability to: Perform the most difficult and complex duties re-
lated to wastewater solids handling and composting operation and
maintenance; recognize and react to process changes and demands;
operate heavy equipment ; use personal computer and standard
software to tract and monitor solids handling operations; and
provide lead supervision and training to lower level personnel.
EVIDENCE OF QUALIFICATIONS
Any combination of experience and education that would likely
provide the required knowledge and abilities is qualifying, sub-
ject to the following minimum requirements:
Experience: Four years of experience performing water and/or
wastewater treatment operations.
l Ec tion: Equivalent to the completion of the twelfth grade
s. _emented by academic course work in chemistry, biology and
r .:nematics.
License or Certificate: Possession of a Class B or. C Wastewater
Treatment Plant Operator ' s Certificate issued by the State of
Colorado and possession of a valid Class B Colorado Driver ' s
License.
�uSzeit
15
SOLIDS HANDLING MECHANIC
DESCRIPTION OF WORK
Perform skilled and semi-skilled work related to the maintenance,
repair, upkeep, and operation o£ the City of Longmont Wastewater
solids handling equipment for dewatering, sludge digestion, land
application and composting.
SUPERVISION RECEIVED AND EXERCISED
Immediate supervision is provided by the Solids Handling
Operators. Technical or Functional supervision may be provided
by higher level Plant Mechanic personnel:
EXAMPLES OF DUTIES
Duties may include, but are not limited to, the following: Es-
tablish and maintain a regular inspection schedule of solids han-
dling facilities ; perform a wide variety of maintenance and
repair tasks in the servicing of the solids handling facility
equipment; perform maintenance and repair of heavy equipment,
pumps , fans , motors , drive systems , electrical equipment ,
sensors, and chemical feeders; calibrate feeder systems and other
equipment such as flow meters, pumps, fans, and valves; perform a
variety of preventive maintenance tasks on mechanical and
electrical equipment including loaders , trucks , material
handling, and dewatering equipment ; assist in the design and
fabrication of a variety of tools , pumps , valves, and piping
systems ; purchase and obtain authorized supplies and materials;
inspect and monitor electronic measuring devices; train and as-
sist less experienced personnel ; maintain up-to-day and accurate
records and logs of operating conditions of equipment and main-
tenance work performed; perform carpentry, masonry, and electri-
cal duties as required; skillfully use a variety of tools and
equipment including pipe cutters and threaders , welding
equipment, drills and grinders, and electrical test instruments;
maintain and service tool and equipment used in solids handling
facility maintenance; perform snow removal duties as required;
-erform related duties as assigned.
?CATIONS
Knc.. of: Methods, procedures, tools, parts, and materials
used in h e operation and maintenance of mechanical and electri-
cal equipment and machinery used for handling, treating, and dis-
posal of wastewater solids; safe and efficient work practices in-
volving complex electrical, electronic and mechanical equipment;
and routine record keeping methods and procedures .
Ability to: Perform routine and preventive maintenance tasks on
electrical and mechanical equipment; identify mechanical problems
and recommend effective corrective courses of actions; perform
maintenance work involving physical stamina; read and interpret
blueprints, electrical schematics, construction drawings, and
maps; maintain routine logs and records ; perform work in emer-
gency situations as necessary; work with considerable indepen-
dence and initiative ; use power and hand tools in repair and
20 �,'^
v, .
maintenance tasks ; and train and assist less experienced
personnel.
EVIDENCE OF OUALIFICATIONS
Any combination of experience and education that would likely
provide the required knowledge and abilities is qualifying, sub-
ject to the following minimum requirements:
Experience: Three years of increasingly responsible experience
in the maintenance and repair of electrical and mechanical
machinery typical to that found at water and/or wastewater treat-
ment facilities.
Education: Equivalent to completion of the twelfth grade.
License or Certificate: Possession of a valid Colorado Driver' s
License.
21
SECTION IV
COMMUNICATION
Serious problems can develop with equipment and/or process per-
formance if communication is inadequate. For this reason com-
munication is emphasized in the plan of operation by making it a
Section unto itself . Generally speaking there are four key
levels within the City structure where formal communication must
take place: between City Council and the Director Water/ Was-
tewater Utilities; between the Water Quality Director and the
Treatment Plant Operations Manager; between the Operations Super-
visor and the Solids Handling Operations Supervisor; and between
the Solids Handling Operations Supervisor and the Water Quality
Laboratory Supervisor. It is understood that there will always
be informal communication at all levels. It should also be noted
that effective communication is the responsibility of all
personnel .
CITY COUNCIL - DIRECTOR WATER/WASTEWATER UTILITIES
Formal communication between the City Council and the Director
Water/Wastewater Utilities can be accomplished through
directives . The reverse communication can be accomplished
through written and oral presentations to the City Council and
through the Annual Water/Wastewater Utilities report. At each
regular City Council meeting the Director Water/Wastewater
Utilities should report on the status of the budget, personnel,
and any other items of special interest . The annual report
should be prepared at least 3 months prior to budget preparation.
It sho,223 contain a separate detailed section describing the
t, ,rdling aspects of the wastewater treatment facility for
t: sr. A suggested outline of the contents of such a solids
ha.:c._.ing section is as follows:
Annual Water/Wastewater Utilities Report
WASTEWATER SOLIDS HANDLING
1 . SOLIDS HANDLING AND DISPOSAL CAPACITY
2 . OPERATIONS
a. Staffing
b. Equipment
c. Financial Data
d. Studies and Improvements
3 . PERFORMANCE HISTORY
a. Sludge Production/Thickener Performance
b. Digester Usage
c. Digested Sludge Monthly Analysis For Land Application
d. Volume of Sludge Land Applied
e. Belt Filter Press Performance
f. Composting
g. Finish Compost Analysis
h. Finish Compost Utilization
22 Pre '> �
ALA
4. EXISTING AND PROPOSED SOLIDS HANDLING REGULATIONS
a. Existing Performance Standards
b. Proposed Performance Standards
c. Potential Impact of Proposed Standards
To supplement the reports , the City Council should tour the
solids handling facilities with the Director Water/Wastewater
Utilities at least once a year and preferably much more
frequently. One tour could be made after the annual report has
been submitted and before the next year' s operating budget is
adopted. This will provide the opportunity to see "first hand"
what is going on and better understand the needs o£ the Solids
Handling Group.
WATER OUALITY DIRECTOR - TREATMENT PLANT OPERATIONS MANAGER
Formal communication between the Water Quality Director and the
Treatment Plant Operations Manager concerning the solids handling
facilities should be established through a monthly written and
oral report. An example written report is shown in Figure IV-1.
The purpose of this report is to update the Water Quality Direc-
tor on the operation and maintenance status and other needs.
OPERATIONS SUPERVISOR - SOLIDS HANDLING OPERATIONS SUPERVISOR
Formal communication between the Operations Supervisor and the
Solids Handling Operations Supervisor should be in the form of
staff meetings and a weekly written report. An example
en report is shown in Figure IV-2 . Attendence at staff
1 _atings should include the operations supervisor the solids han-
dling operations supervisor, and lead plant and solids handling
operators. Through these meetings the staff members can be in-
formed of how current policies and proposed changes may affect
them. These meetings can be an effective tool in keeping lines
of communication open and operator morale high. The meetings
should also be used to discuss current process control
strategies, previous week' s problems, and proposed process con-
trol modifications. An example weekly staff meeting agenda is as
follow:
Proposed Staff Meeting Agenda
1. Discuss plant and solids handling facility performance for
the previous week.
2 . Discuss current process control strategy.
3 . Discuss any changes that have been made or are proposed in
the standard operation and maintenance procedures at the
plant or the solids handling facilities.
4 . Discuss activities of the wastewater treatment facility as a
whole such as special studies being undertaken or solids
disposal options.
I 5. Answer questions.
23 Cy.r:.n
SOLIDS HANDLING OPERATIONS SUPERVISOR - WATER OUALITY LABORATORY
SUPERVISOR
Formal communication between the Solids Handling Operations Su-
pervisor and the Water Quality Laboratory Supervisor is as shown
by the solid lines in Figure III-2 . This line of communication
should be followed when new or different laboratory tests are
needed. On a routine basis, the operational lines of communica-
tion shown by dashed lines in Figure III-2 should be followed.
Should there be a conflict in laboratory work requested by the
Operations Supervisor or the Solids Handling Operations
Supervisor, then the Water Quality Director will either resolve
the conflict or set the priority for the work to be performed.
The Water Quality Laboratory has its own computerized system for
tracking and documenting samples and testing. This system should
adhered to.
1
26
SECTION V
FACILITIY OPERATION AND MAINTENANCE PROGRAM AND MANUAL
A. Operational Strategy And Unit Process Control
The solids handling processes to be used as a result of this
solids handling project include gravity sludge thickening,
belt filter press dewatering , aerated static pile
composting, and contract hauling of anaerobically digested
sludge to land application sites . This combination of
processes was developed to provide flexibility in wastewater
sludge disposal while also meeting the disposal requirements
established by the Colorado Department of Health. A general
description of the monitoring and control strategy for each
of these unit processes follows . A more detailed and
specific discussion of the operation of each will be
developed as part of the Operation and Maintenance Manual.
Gravity Sludge Thickening
Gravity thickening is accomplished in a circular tank
similar to a clarifier. Dilute sludge is feed at as con-
stant a rate as possible into a center well and allowed to
settle and compact. The thickened sludge is withdrawn from
the bottom of the thickner and a continuous supernatant flow
is returned to wastewater treatment plant headworks. The
existing and new sludge thickeners may be operated in-
dividually or simultaneously in a parallel mode. Flow of
( _ udge to and from the thickeners will be controlled by
-,.rally adjusted valves and by pumps. Thickened sludge is
pimped either to the existing anaerobic digesters or to the
belt filter presses in the new dewatering building. The su-
pernatant will flow by gravity to the headworks pump
station. Storage of sludge will be accomplished by allowing
the sludge blanket in the thickener to increase. Sludge
levels should be monitored and odor levels noted to avoid
nuisance conditions. "Sweetening" water will be pumped to
the thickeners from the effluent splitter box on the east
side of former No. 2 final clarifier during times that large
amounts of sludge are being stored.
Typical process control measurements and frequency are as
follows:
Measurement Frequency
Volume Pumped to Thickener daily
Thickened sludge total solids daily
Thickened Sludge Volume Taken
from Thickener daily
Supernatant Suspended Solids daily
Supernatant BOD twice weekly
Belt Filter Press Dewaterinq
Thickened sludge from the gravity sludge thickeners will be
pumped to the belt filter presses. Dewatering is achieved
27
r092,-
by forcing the water from the sludge under high pressure by
squeezing it between two porus belts . To aid in the
dewatering process, a polymer is mixed with the thickened
sludge just prior to the press. The belt filter presses are
most effectively operated by personnel at the equipment
rather than in a remote operations room. This allows for
constant monitoring of belt speed and tension, polymer
dosage, and general status of the press equipment. Key ad-
justments to be made by the belt press operator to optimize
performance are sludge feed rate, polymer type and feed
rate, press belt speed and tension, and conditioner belt
speed.
Typical process control measurements and frequency are as
follows:
Measurement Frequency
Sludge Feed Rate (gpm) daily
Sludge Feed Total Solids daily
Polymer Feed Rate (gpm) daily
Polymer Total Weight Used daily
Dewatered Sludge Total Solids daily
Weight Dewatered Sludge Produced daily
Filtrate BCD twice weekly
Filtrate flow rate (gpm) daily
Filtrate total solids daily
Filtrate Suspended Solids daily
Press Belt Speed Setting daily
( Press Belt Tension Setting daily
Conditioner Belt Speed Setting daily
Aerated Static Pile Composting
Dewatered, undigested sludge cake will be trucked to the
composting facility where it will be mixed with previously
composted material. The aerated static pile method of com-
posting will be used. Active composting will occur for 28
days followed by 30 days of curing.
During the composting period, biological activity in the
compost pile will generate heat which causes pathogens to be
killed, volatile solids to be destroyed, and the material to
dry. If heat generation is not managed, the compost pile
will become so hot that the biological activity will stop.
To control pile temperature , which in turn controls the
other functions of the composting process , air is blown
through the compost pile with a fan . The amount of air
blown through the pile is controlled by temperature probes
in each pile. This method of compost process control is
generally known as the "Rutgers Strategy" and was success-
fully demonstrated in the pilot work carried out by the
University of Colorado Civil Engineering Department for the
City of Longmont.
28 `rs�,. �
0.-�
Generally, the operation of this composting facility will be as
follows:
a. Sludge cake will be brought to compost facility in dump
trucks 5 days per week.
b. Dump trucks will empty cake into a sludge transfer
enclosure in the mixing building.
c. Recycle material either from storage or fully cured
material from a curing pile will be brought by bucket
loader to the mixing building and placed directly into
a mixing unit.
d. Sludge will be moved from the transfer enclosure
directly to a mixing unit with a large skidsteer
loader.
e. After mixing sludge cake and recycle together in a
mixing unit, the mixture will be discharged into a .
small pile next to the mixing unit.
f. A bucket loader will move mixed material to the com-
posting pile to form the core of new pile.
g. A new compost pile will be constructed for each day
that sludge cake is brought to the composting facility.
h. 24 composting pile spaces will be provided to allow for
a gap of 4 pile spaces between the newly constructed
composting pile and the composting pile just becoming
28 days of age.
i. Construction of composting piles will progress in a
counterclockwise fashion around the composting/curing
building.
j . Bed and cover material for the new compost pile will be
( moved by bucket loader from the compost pile which has
just attained the age of 28 days .
k. Material not used for bed or cover of a new compost
pile will be moved by bucket loader to a curing pile.
1 . Composting will take place for 28 days under aeration
and result in material having total solids content of
60 percent and meeting PFRP requirements.
m. Each curing pile will hold the material removed from
seven compost piles.
n. Curing will take place for 30 days under aeration and
result in material having a total solids content of 70
percent.
o. After curing, material will be moved by bucket loader
either to a mixing unit for blending with sludge cake
or to the storage pile in the storage building.
p. Storage of finish compost and/or amendment will be in
extended type piles in a storage building located
across from the mixing building.
Typical process control measurements and frequency are as
follows:
Measurement Frequency
Temperature Continuously at 2 locations with
(Each Pile) sensor probes.
f
Twice daily at pile ends with manual
thermometers.
29 cm 6"Cr—""'
Weight and Volume Each day that new pile made;
of new pile components for sludge cake and recycle.
New Pile Dimensions Each day that new pile made
(Overall dimensions &
thickness of cover &
bedding)
Fan run time Daily for each pile
Compost Mixture
Total Solids Once when pile is constructed, twice
during composting, and once when
pile is torn down.
Free Air Space Once when pile is constructed and
once when pile is torn down.
Bulk Density Once when pile is constructed and
once when pile is torn down.
Volatile Solids Of incoming sludge cake and when
when pile is torn down.
Total Nitrogen Of incoming sludge cake and when
pile is torn down.
Finish Pile Dimensions Once before pile is torn down.
Contract Hauling of Anaerobically Digested Sludge
This is the present means of sludge disposal used by the City of
Longmont wastewater treatment plant. To preserve flexibility in
sludge disposal options, these facilities are being retained at
the treatment plant. With this disposal option, sludge is
anaerobically digested and then hauled as a liquid to land dis-
posal sites. The hauling and application onto the land is done
by companies which contract with the City to perform such
services . The details of this disposal unit operation are
provided in the existing 0&M documentation for the wastewater
treatment plant.
B. Maintenance Management System
Overall responsibility for proper maintenance of all the was-
tewater treatment facilities lies with the Maintenance Supervisor
who reports directly to the Treatment Plant Operations Manager.
Because the composting facility is remote from the wastewater
treatment plant, a mechanic is being assigned to the solids han-
dling group. However, each individual associated with the solids
handling group plays an important role in keeping the records
current and accurate. The appropriate use of field report forms,
maintenance management database software, and active dialogue be-
tween the operations personnel , clerical personnel , and data
processing personnel will help insure the success of the Solids
Handling Maintenance Management Program.
30
z ,
The wastewater treatment plant has a computerized warehouse in-
ventory tracking system which is a key element of the maintenance
management system for the plant. The Solids Handling Operations
Supervisor (SHOS) will be responsible. for developing a similar
system for the composting facility. Also, the City of Longmont
is upgrading the hardware and software used citywide in the over-
all management system. The Solids Handling Operations Supervisor
will need to evaluate this new system to determine if it has com-
patible hardware or software for use in the maintenance manage-
ment system of the solids handling facilities.
Maintenance tasks are divided into three categories:
1. Preventative Maintenance
2 . Corrective Maintenance
3 . Housekeeping
Preventive maintenance tasks are routine tasks (such as greasing
mechanical equipment) that are performed to keep the equipment in
good working order. Corrective maintenance tasks are tasks per-
formed to repair inoperable or malfunctioning equipment .
Housekeeping duties include such things as building maintenance
and care of grounds.
The SHOS will have the responsibility of seeing that an adequate
maintenance program is developed and implemented for the solids
handling facilities and in particular the new composting
facility. This will involve the development of maintenance
schedules and a database for record keeping. Routine preventive
maintenance tasks will be performed by the solids handling
operators and corrective maintenance will be performed by the
solids handling mechanic with assistance from the operators.
In preparing the Solids Handling Maintenance Management System,
the SHOS will receive assistance from the consulting engineer.
Preliminary submittals of equipment O&M material furnished by the
various manufacturer' s will be routed by the consulting engineer
to the SHOS. Further, the consulting engineer will make recom-
mendations to the SHOS based upon work performed in preparing the
O&M manuals. Likewise, the SHOS will provide direction to the
consulting engineer regarding the maintenance management system
structure in order that the O&M manual can be integrated with it.
Organization and planning the maintenance management system will
be done during construction so that it can be implemented along
with the actual start-up of equipment . The following is a
schedule for the implementation of the maintenance management
system:
February 15, 1990
Begin Development of Maintenance
Management System
May 25, 1990
Draft O&M Manual materials due from contractors
June 1, 1990
Begin to investigate use of new City maintenance management
system hardware and software.
31
June 15, 1990
Submit Draft Plan for Maintenance Management System to State
for review.
July 2 , 1990
Receive State approval of Maintenance Management System
Draft.
July 2 , 1990
Begin developing maintenance management system forms.
August 1, 1990
Begin development of maintenance schedule sheets.
October 1, 1990
Complete maintenance management forms and schedule sheets.
October 15, 1990
Submit Final Plan for maintenance management system to State
for review.
January 2, 1991
Implement Maintenance Management Program at In-Plant
facilities.
January 7, 1991
Implement maintenance management program at compost
facility.
C. Emergency Response Plan
An emergency response plan provides the Solids Handling Group
with a plan and schedule of items to be addressed in emergency
situations such as power outages, fire, equipment failures, or
natural disasters.
In any emergency situation at either the treatment plant or the
composting facility, the Operations Supervisor will have respon-
sibility for coordinating the activities o£ the treatment plant
staff to insure that the best possible treatment of wastewater
and sludge disposal practices are provided. Coordination of ac-
tivities at the composting facility will be by the Solids Han-
dling Operations Supervisor. Assistance from other City person-
nel (water operators and field and maintenance personnel) will be
obtained as necessary.
The Solids Handling Operations Supervisor will be responsible for
developing the emergency response plan for the solids handling
project. This plan will be coordinated with the existing plan
for the wastewater treatment plant . Recommendations for the
emergency operation of specific equipment and unit processes will
be included in the O&M Manual prepared by the consulting
engineer. As part of the start-up training for the Solids Han-
dling Group, a workshop will be held to review emergency opera-
tional procedures.
The emergency response plan must be reviewed routinely by the
Treatment Plant Operations Manager, the Operations Supervisor,
and the Solids Handling Operations Supervisor, as well as other
groups (such as local fire and police department personnel) that
may be involved in responding to an emergency situation. To keep
the operations staff informed of emergency procedures, routine
reviews of the emergency operations plan should be included as
part of an on-going staff training program.
32
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n , v�
iy�-1=d
The following is a schedule for developing and implementing the
Emergency Response Plan:
February 15, 1990
Begin Development of Emergency Response Plan
June 15, 1990
Submit Draft of Emergency Response Plan to State for Review
October 1, 1990
Complete Emergency Response Plan
January 2 , 1991
Conduct Tour of In-Plant Facilities with Police and Fire
Department Personnel
January 10, 1991
Conduct tour of Compost Facilities with Police and Fire
Department Personnel
March 1, 1991
Emergency Operationsl Procedures Workshop
D. Laboratory Requirements
The Longmont Water Quality Laboratory located at the treatment
plant site is equipped to perform all of the analytical proce-
dures required for treatment process monitoring and control ,
sludge quality and stabilization , reporting requirements as
stated in the plant NPDES permit , and industrial wastewater
monitoring for the pretreatment program. This Laboratory follows
procedures outlined in Standard Methods for the Examination of
Water and Wastewater and in the EPA Manual of Methods For Chemi-
'--:alysis of Water And Wastes. Samples are periodically split
( _parate analysis by the Colorado Department of Public Health
as a quality control check.
Solids handling monitoring requirements for which the Longmont
Water Quality Laboratory is not equipped to handle are sent out
to an independent testing laboratory for analysis. Such tests
are those pertaining to soil analysis, plant tissue analysis, and
viral analysis.
The Solids Handling Operations Supervisor will be responsible for
coordinating operational laboratory needs with the Water Quality
Laboratory Supervisor. A small bench laboratory will be provided
at the composting facility operations building to aide in daily
operation of the composting facility. However, the principal
source of process monitoring data will be the water quality
laboratory at the treatment plant.
Specific laboratory testing to be performed at the water quality
laboratory are listed below by unit process:
Gravity Sludge Thickening
Total Solids
Suspended Solids
Biochemical Oxygen Demand (BOD)
Belt Filter Press Dewatering
Total Solids
Suspended Solids
BOD
3 3 did'C92.AD
Aerated Static Pile Composting
Total Solids
Volatile Solids
Total Nitrogen
Organic - N
Total Ammonia - N
Aluminum
Cadmium
Copper
Iron
Lead
Nickel
Phosphorus
Zinc
PCB
The small bench scale laboratory at the compost facility opera-
tions building should be equipped to measure the total solids
content, bulk density, and free air space o£ sludge cake ,
compost, and any amendments which may be used.
Laboratory needs for contract hauling of anaerobically digested
sludge have already been implemented because this is the present
method of sludge disposal. As this disposal alternative is being
retained as an option, those laboratory needs will continue.
E. Operation And Maintenance (O&M) Manual
An Operation and Maintenance (O&M) Manual for the existing was-
tewater treatment plant has been previously prepared by McCall ,
Ellingson, Morrill, Inc. This O&M Manual was approved by the
Colorado Department of Health in February, 1987 . As part of this
solids handling project, changes/additions are being made to the
solids handling facilities at the wastewater treatment plant.
Consequently, portions of this existing O&M Manual will need to
be updated. In particular, the existing O&M manual will need to
be revised to reflect the following:
A) Addition of a new sludge thickener
1) Provide operational procedures for two thickners.
2) New thickener equipment
3) New Thickened Sludge Pump Station
4) Replacement Pumps in Existing Sludge Control Bldg.
5) New Submersible Pump Station
6) New flow meeting devices
34 r �ro
B) Belt Filter Press
1) Provide operational procedures for two belt presses
2) New filter press
3) New polymer feed system
4) Air compressor for filter press
5) New plant water pressure booster pumps
6) New flow metering devices
7) New monorail and hoist
8) New HVAC Equipment
9) New Electrical Equipment
C) New Sludge Truck Loading Facilities
1) Loading operations
2) Bin gate on Sludge Hoppers
D) New Waste Sludge Gas Burner
Because the aerated static pile composting facility is located at
a site away from the existing wastewater treatment plant, a new
O&M manual will be prepared for it. The composting facility O&M
manual will be developed to provide specific information concern-
ing operation and maintenance of that facility. A tentative out-
line for the Composting O&M Manual is shown below:
TENTATIVE COMPOSTING FACILITY O&M MANUAL OUTLINE
Table of Contents
I . Introduction
- Statement of Purpose
- Description of Composting Facility
- Discussion of Personnel Responsibilities
- Process Control
- Maintenance
- Reporting
- Safety
Emergencies
- O&M Manual User Guide
II. Composting Fundamentals
Material Properties
- Airflow and Temperature Control
- Odor Control
- References
III . Composting Processes
- Description of each compost process
(mixing, composting, curing, final disposition)
- Schematic diagram of process layout
- Design Parameters (Table)
Major Components
Equipment
Description and location of controls
Start-up , typical operation , optional modes of
operation, shut-down
- Operational Concepts and Controls
- Relation of Specific Controls to Concepts f\
Computer control, reporting, and analysis tfe
35
X. Personnel
Job Descriptions and Qualifications
Certification Requirements
XI. Electrical System
- Power Sources
- Power Requirements
Locations o£ All Power Switches
- Wiring Diagrams
XII. Utilities
- Water
- Sanitary
Electrical
- Telephone
XIII. Appendices
- Manufacturer' s Equipment Literature
Primary responsibility for the development of the composting
facility O&M manual and updating the existing wastewater treat-
ment plant O&M manual rests with the consulting engineer retained
by the City during construction and start-up. However, it is
considered to be very important that the Solids Handling Opera-
tions Supervisor also has an active role in the preparation of
these documents. This is a principal reason for assigning/hiring
the Solids Handling Operations Supervisor at the start of
facility construction. The schedule for development of the O&M
Manual documents is as follows:
April 2 , 1990
Begin O&M manual preparation
May 25, 1990
Draft O&M .Manual materials due from Contractors
June 15, 1990
Submit Draft O&M Manual Documents to State for Review
July 2 , 1990
Receive State approval of Draft O&M Manual Documents
September 14 , 1990
Final O&M Manual materials due from Contractors
October 15, 1990
Submit Final O&M Manual Documents to the State for Review
November 15, 1990
Receive Final O&M Manual Document Approval from State
September 15, 1991
Begin one-year review of O&M Manual Documents
October 15, 1991
Update O&M Manual Documents based on first year operating
experience
F. Dynamic Policy and Procedures Manual
The City of Longmont has developed what they call a "Dynamic
Policy And Procedures Manual" to supplement information in the
O&M Manual . This additional manual is a step by step set of
directions for performing specific tasks connected with the
operation of specific treatment equipment. It is called
"Dynamic" because it is continually changed to reflect new
operating conditions. The existing manual will need to be
revised to include the new in-plant equipment. Likewise, new
manual sections will be required for the composting facility.
For the compost facility, this manual will need to address the
mix ratio o£ dewatered sludge to finish compost, new pile con-
struction and cover layer thickness, and fan control . Each of
these topics has changing procedures depending on the season and
character of the dewatered sludge cake.
The Solids Handling Operations Supervisor will be responsible for
preparing new and updating existing sections as appropriate. The
schedule for revising and updating this document is as follows:
September 1, 1990
Prepare draft Dynamic Policy & Procedures Manual
April 1, 1991
Finalize Dynamic Policy & Procedures Manual
October 15, 1991
Update Dynamic Policy & Procedures Manual
G. Operation During Construction And Start-up
From a construction and start-up point-of-view, the solids han-
dling project consists of two parts- the work at the treatment
plant and the construction of a new composting facility. Because
solids handling unit operations are a batch type process, the ex-
isting wastewater treatment facility will be able to continue
operating as it has in the past. Doing this will require a few
( temporary facilities to be constructed by the Contractor and will
necessitate that certain tasks are performed during particular
time periods. These requirements are identified for the In-Plant
Contractor in Section 01311 of the project specifications.
Key construction coordination considerations for solids handling
facilities at the wastewater treatment plant are detailed in Sec-
tion 01311 of the project specifications and as follows:
1. The existing gravity thickener is critical to the plant
operation and shall not be taken out of service until the
new thickener is operational .
2 . The plant staff shall adjust the valves in the digester
building to direct flow of digested sludge to the temporary
loading facility. This facility shall be adjusted so that a
minimum of 12 feet of clearance is provided under the load-
ing pipe. No work shall commence until the loading facility
is relocated.
3 . Relocation of the existing 18-inch trickling filter recycle
line shall be done after a minimum of 2 days notice to plant
staff. The line shall not be out of service for more than
eight hours. If more time is needed, temporary piping and
pumping shall be provided.
4 . Relocation of the waste gas burner shall be done by install-
ing the new burner and piping first and making the connec-
tion to the existing pipe when the new burner is in operat-
ing condition. The existing gas burner may not be out of
service for more than 24 hours.
38 ar 5-Q 9)
Aim .t
5 . The new dewatering building shall be constructed so that
piping modifications to the existing mechanical building are
made without taking lines out of service for more than eight
hours.
6. Access to the existing mechanical building truck loading bay
must be maintained from March 1 through May 30, unless the
new belt press is in operation. The existing belt press may
not be relocated during these months unless an alternate
sludge dewatering system is available.
7 . Modifications to the sludge control building, piping and
pumps shall be done so that one pump is in operational
status at all times and such that thickened sludge may be
sent to either the digesters or belt press as needed.
8 . Installation of yard piping shall be coordinated so that any
crossing or relocation of existing utilities does not
prevent the downstream processes from operating.
The City will provide several items to the Contractor for incor-
poration into the new in-plant work. These items are as follows:
1. 500 KVA transformer
2 . Existing belt filter press (reference Section 01018 ,
article 3 . 02 of the project specifications)
3 . FRP v-notch weir plates and baffles for installation in
the existing thickener.
Sludge disposal throughout construction will continue as before
by using contract haulers to land apply anaerobically digested
sludge. When it is time to run performance tests on the new and
( relocated belt filter presses, it will be necessary to use un-
digested sludge as this is what will be sent in the form of cake
to the composting facility. Disposal of this undigested
dewatered sludge cake will need to be at the City o£ Longment
Landfill. The landfill is presently scheduled to close December
31, 1990 . However, the landfill operator will reserve room to
accept this cake should the landfill need to close before start-
up testing of the belt filter presses.
The composting facility is new and not located at the wastewater
treatment plant. Consequently, it can be constructed indepen-
dently of any existing wastewater treatment or solids handling
operations. The City of Longmont will be purchasing, installing,
and programming a computer control system for the compost
facility. By doing so, the City will be assured of a computer
control system fully compatible with the existing system at the
wastewater treatment plant. Also, in preparation for start-up of
the composting facility, the City will need to do the following:
1. Acquire an amendment (such as wood chips or animal manure)
to mix with the sludge cake because no recycle material is
available.
2 . Furnish the operations building, lunch room, and bench
laboratory.
3 . Stock the compost facility with miscellaneous small tools
necessary both for maintenance and facility operation.
4 . Purchase a dump truck through City Fleet Purchase.
39
far s2
Operation of the wastewater treatment facilities during construc-
tion will involve a coordinated effort on the part of the
contractor, the consulting engineer and the plant staff. The
items presented above have been detailed in the project
specifications for each project to insure that the contractor is
aware of his responsibilities with regard to providing for con-
tinuous operation of the plant during construction. Section
01200 in each set of project specifications describes project
meetings to be held throughout construction to facilitate
communications. The consulting engineer will be available during
construction and will be familiar with this operations plan. In
addition, the consulting engineer will provide a resident en-
gineer who will work with the plant staff to see that the con-
tractor adequately provides the necessary piping and pumping
facilities in order that the plant can be operated according to
plan. The plant staff will be responsible for the actual opera-
tion of the plant. The staff will also need to be familiar with
this plan for operation during construction and will work with
the consulting engineer to resolve any problems that may arise in
implementing this plan. A preconstruction conference with the
Contractor will be held at the start of construction to ensure
that all parties are knowledgeable in their role for continuous
operation of the wastewater treatment plant. Shortly after the
preconstruction conference for each project, the Contractor is
required by Section 01300 , article 1 . 02 to submit a detailed
schedule of his anticipated construction activities . The
schedule submitted should specifically address the items dis-
cussed in this Plan of Operation section.
A schedule of tasks to be performed by the City follows:
July 16, 1990
City Purchase Compost Facility Computer Control Equipment
August 20, 1990
City Begin Programming Compost Control Computer
September 17, 1990
Begin Work to identify and obtain all necessary safety
material and equipment.
October 8 , 1990
Arrange for polymer for belt press testing
October 10, 1990
Arrange with Longmont Water Quality Laboratory for belt
press testing
October 31, 1990
Complete Identification and stocking of In-Plant safety sup-
plies
November 1, 1990
Arrange for Composting Start-up Amendment
November 5, 1990
City purchase dump truck
November 7 , 1990
Begin 30 Day Performance Testing of Belt Filter Presses
December 3 , 1990
Delivery small load of start-up amendment to compost
facility for equipment testing
December 26, 1990
Purchase compost facility small tools, lab equipment, and
Operations Building Furnishings
C n",.
40 t. ^'s
_ .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
January 4, 1991
Complete identification and stocking of compost facility
safety supplies
January 7 , 1991
Begin installing compost control computer
February 1, 1991
Deliver start-up amendment to compost facility
February 23, 1991
Compost control computer operational
H. Start-up Process Control Testing
The project specifications for the In-Plant work and for the
Composting Facility each detail the system testing to be
performed by that project' s Contractor. For the In-Plant
Work, the following tests are to be performed prior to ac-
ceptance of the work:
System Tested Pro9 . Spec. Ref.
Belt Filter Press
Relocated Unit Section 01018
New Unit Section 11365
Rotary Lobe Pumps Section 11309
Submersible Pumping System Section 11316
Gravity Sludge Thickener Section 11363
Sludge Gas Handling Equipment Section 11388
Monorail And Hoist System Section 14900
( Hoist And Lift Truck Section 14910
PVC Chemical Lines Section 15064
PVC Drains And Vent Section 15064
DIP Sludge Lines Section 15072
HVAC Performance Testing Division 15
Electric Motors And Electrical
Distribution System Division 16
Flow Metering Systems Section 16900
For the composting facility, the following tests are to be
performed prior to acceptance of the work:
System Tested Prole Spec. Ref.
Sanitary Sewer Section 15064
Water System Section 15064
HVAC System Testing Section 15600
Aeration Piping Section 15895
Electric Motors And Electrical
Distribution System Section 16001
41 ce "# =q
SECTION VI
START-UP TRAINING AND ASSISTANCE SERVICES
A. Staff Training Program
Prior to formal training activities, the consulting engineer
retained by the City will assist the Solids Handling Opera-
tions Supervisor (SHOS) in developing programs to address
personnel training needs in the following areas:
1. Process Control
2 . Maintenance
3 . Safety
4 . On-going Training
The outline for a program in each of these areas , as
developed by the SHOS, will be included in the O&M Manual.
The consulting engineer will provide guidance and technical
assistance to the SHOS as he determines specifically how
each program is to be structured and compile the necessary
information and materials required before the programs can
be implemented.
The Solids Handling Group will receive hands-on instruction
on the correct operation and maintenance procedures for all
of the major equipment from representatives o£ the equipment
manufacturers at the time of equipment start-up. For the
In-Plant Work, manufacturer ' s field services will be
provided for the followig:
Equipment Prol . Spec. Ref.
Package Polymer System Section 11242
Rotary Lobe Pumps Section 11309
Submersible Pumping System Section 11316
Gravity Sludge Thickener Section 11363
Belt Filter Press Section 11365
Sludge Gas Handling Equipment Section 11388
Sludge Hoppers Section 13901
Monorail And Hoist Systems Section 14900
Adjustable Frequency Speed
Control Systems Section 16453
Instrumentation System Section 16900
For the Compost Facility, manufacturer' s field services will
be provided for the following:
Equipment Proj . Spec. Ref.
Mixer Section 11355
Wheel Loader Section 14515
Skid-steer Loader Section 14516
Composting Fans Section 158,60
Curing Fans Section 15860
Odor Control Fans Section 15860
Roof Ventilator Fans Section 15871
Aeration System Pressure Gages Section 15895 rin ,,,4
42 ` ` .
Also, in conjunction with the start-up of the solids han-
dling facilities, the consulting engineer will conduct six
i start-up training workshops. The .purpose of these workshops
will be to give all members of the Solids Handling Group a
sense of identity and to review the solids handling
facilities - particularly the new compost facility. The
principal subject and target date for these semi-formal
workshops are as follows:
Workshop Principal Subject Target Date
1 Dewatering Fundamentals October 23 , 1990
2 Solids Handling Group organi-
zation, personnel responsibilities,
and lines o£ communication November 2 , 1990
3 Solids handling group operators
tour similar compost facilities
(e.g. Denver Metro and/or Fort
Collins) December 10, 1990
4 Health related aspects and safety
at solids handling facilities January 21, 1991
5 Composting Fundamentals February 1, 1991
6 Emergency operational
procedures March 1, 1991
Thre adgenda for each of the above workshops should include
a time for discussing operational difficulties or successes
since the last workshop and a time to plan .future opera-
tional needs.
After the solids handling facilities at the wastewater
treatment plant have been placed into service, the consult-
ing engineer will continue to be available to the Solids
Handling Group for consultation on an as needed basis.
The consulting engineer's involvement will decrease as the
solids handling operator' s understanding of the new equip-
ment increases.
After the composting facility has been placed into service,
the concept of semi-formal workshops with the solids han-
dling group should continue . These workshops should
generally be conducted by the Solids Handling Operations
Supervisor. However, outside consultants should be brought
in for guidance on specific topics as may be warrented .
Composting is primarily an art which has entered into the
arena of science. In order to achieve composting, many in-
terrelated processes such as biology , chemistry,
thermodynamics, and material balances must all be made to
work together. It will be the purpose of these workshops to
l guide the solids handling group in sorting out these inter-
relationships - one at a time. Each workshop should first
review the skills previously learned through operating the
43
facility and then introduce a new process variable or skill
to be developed. Suggested topics for these composting
workshops include:
1. Bench laboratory techniques
2 . Mixing
3 . The starting mix
4 . Fan Fundamentals
5. Temperature Control
6. Odor Control
7 . Regulatory Requirements
Because composting is a slow process, these workshops can be
scheduled at two to four week intervals. Also, because am-
bient temperature plays a role in composting, operational
techniques will change with the seasons. Consequently, it
is important that these workshops continue throughout the
first year of operation, although the frequency should
decrease as the overall understanding of the solids handling
group increases.
At the termination of the start-up training, the new solids
handling facilities should be functioning efficiently and
the solids handling group should be comfortable and confi-
dent in their ability to make it continue to do so.
It will be the responsibility of the Solids Handling Opera-
tions Supervisor to develop and implement an on-going train-
ing program. Such a program could consist of formal in-
plant training seminars used to fulfill the needs of the
solids handling group as far as theoretical background and
understanding are concerned. Training activities sponsored
by outside organizations include operator training courses,
seminars and association conferences. These training ac-
tivities will supplement the in-plant training and will be
helpful in developing the theoretical background and under-
standing of operators as well as acquainting them with new
processes and developments in the solids handling, disposal,
and composting fields.
In addition to formal training activities, the City should
subscribe to several technical journals and magazines and
provide reference books for use by the solids handling group
- particularly as related to composting. Such books and
magazines will provide the staff with opportunities to
upgrade technical skills and stay abreast of developments in
the composting and solids handling fields individually.
A schedule for developing and implementing the staff train-
ing program is as follows:
February 15, 1990
-Begin Development of Staff Training Program
June 15, 1990
Submit Draft of Staff Training Program to State for
Review
July 2 , 1990
Receive State approval of Draft Staff Training Program
44c ,3-a
October 15, 1990
Submit final plan for Staff Training Program to State
for Review
December 3 , 1990
Begin Equipment training by Factory Representatives
B. Safety Training Program
A safety program will be developed and implemented to train
the solids handling group in safety precautions and to iden-
tify and correct safety hazards.
The safety program will address the following aspects of
safety:
1. Personnel training
2 . Working environment
3 . Safety equipment
4 . Risk management
The Solids Handling Operations Supervisor (SHOS) will be
responsible for organizing the safety program, including a
record keeping system, and for implementing the safety
program once it has been organized. The safety program for
the new solids handling project facilities will be struc-
tured around the existing program at the wastewater treat-
ment plant.
Safety meetings are held at the wastewater treatment plant
on at least a monthly basis. Off duty personnel will be
( paid overtime wages to attend safety meetings. The meetings
are coordinated with the Risk Manager to include special
safety training sessions such as films and guest lecturers.
In 1978 the City of Longmont began a risk management program
to unify personnel safety training standards and to provide
for a safe working environment at all city operated
facilities. The risk management program addresses three
major areas of occupational safety and liability: loss
prevention, loss control, and loss financing.
The objective of loss prevention is to minimize the occur-
rence of events which cause loss of property or personal in-
jury to city employees. Employee training and selection
play important roles in loss prevention. The City Risk
Manager works closely with the Personnel Department in
matching employee qualifications with job descriptions in
order to minimize the exposure of personnel to potentially
hazardous situations beyond their ability to control . For
example a person with minimal driving skills would not be
given a job driving a sludge truck. Initial job training,
regular safety training sessions , and refresher safety
classes are also an important aspect of the loss prevention
portion of the risk management program.
Wastewater treatment plant personnel are also given the
opportunity, through the risk management program, to take
certified training courses in defensive driving, CPR, and
first aid . There is no charge to the employee for the
45 (PC"`°
safety training courses.
A recommended program structure specific to the solids han-
dling group will be outlined in the O&M manual . The consult-
ing engineer will be available to assist the Solids Handling
Operations Supervisor in organizing and implementing the
program.
The schedule for development and implementation of the
safety program is as follows:
February 15, 1990
Begin Development of Safety Training Program
June 15, 1990
Submit Draft of Safety Training Program to State for
Review
July 2 , 1990
Receive State approval of Draft Safety Training Program
September 17, 1990
Begin work to identify and obtain all necessary safety
material and equipment.
October 15, 1990
Submit Final Safety Training Program to State for
Review
October 31, 1990
Complete Identification and Stocking of In-Plant Safety
Supplies
January 2 , 1991
Conduct Tour of In-Plant Facilities with City Risk
( Manager
January 4 , 1991
Complete identification and stocking of compost
facility safety supplies
January 11, 1991
Conduct tour o£ compost facility with City Risk
Manager.
March 1, 1991
Implement safety training program for Solids Handling
Group. .
C. Consulting Engineer Services
The City will need to contract for the services of a con-
sulting engineer during solids handling facility construc-
tion and start-up of the facilities . Previous sections of
this Plan of Operation have outlined in general the role
that the consulting engineer will play during these phases
of the project. Outlined below is a more specific descrip-
tion of the Scope of Work to be provided by the consulting
engineer during each phase:
Construction Phase Services
1. Review Contractor ' s schedules and schedule of values.
2 . Hold a pre-construction conference with the Contractor.
3 . Review shop drawings, applications forjpayment, and
change order requests.
4 . Make visits to construction site at times appropriate
to the progress of the work. Clan
46 et>"
5. Furnish a full time resident engineer and assistants as
required.
6. Assist City and Solids Handling Operations Superinten
dent with preparation of maintenance management plan,
emergency response plan, staff training program plan,
and safety training program.
7. Utilizing the resources of the wastewater treatment
facilities operation' s staff to the greatest extent
practicable, revised the existing plant O&M manual to
include the new solids handling facilities at the
treatment plant and prepare a new O&M manual for the
composting facility.
8 . Assist the Solids Handling Operations Supervisor with
updating the "Dynamic Policies And Procedures Manual"
to include the work of these projects.
9 . Issue certificates of substantial and final completion
to the Contractor when applicable.
10. Prepare record drawings for each project.
Start-up And Operations Phase Services
1. Conduct six semi-formal start-up training workshops.
2 . Coordinate start-up training provided by equipment
manufacturers.
3 . Assist Solids Handling Group staff with facility start-
up by making periodic visits to the facilities.
4 . Provide as-needed consultation on in-plant solids han-
dling facility operation.
( 5. Provide one-year operation performance certification
and one-year final inspection of facilities.
The consulting engineer selected to perform the above serv-
ices should be completely familiar with the construction
drawings and project specifications. Also, the consulting
engineer should have assisted in the start-up of other com-
posting facilities.
The schedule for consulting engineer services is as follows:
January 30, 1990
Construction Phase Engineering Services Begin
October 1, 1990
Start-up And Operations Phase Engineering Services
Begin
November 19 , 1991
Begin one-year performance certification review of In-
Plant Work.
December 1, 1991
Begin One-year performance certification review of com-
post work.
December 9, 1991
Provide In-Plant one-year Performance Certification
December 24 , 1991
Provide Compost one-year Performance Certification
47 >: ^
SECTION VII
EXPENSES AND REVENUES
A. Salaries
The following is a list of the solids handling group staff
positions, the number of persons required at each level, and
the approximate salary range for that level:
Position Number Salary Range (1)
Solids Handling
Operations Supervisor 1 $35, 000 - $44 , 000
Solids Handling
Operators 4 $23, 000 - $31, 000
Solids Handling
Mechanic 1 $32 , 000 - $34 , 000
(1) Includes payroll taxes and fringe benefits.
B. Operation And Maintenance Costs
Funding for operation and maintenance of the new solids han-
dling project facilities will come from the existing was-
tewater treatment plant operation and maintenance budget.
Labor costs are covered by reassigning existing wastewater
plant positions to the solids handling group. Likewise,
when sludge cake is being composted, contract hauling of
anearobically digested sludge to land application is not
( required. O&M funds saved by not land applying sludge can
be summarized as follows:
Labor costs savings $184 , 000
Contract Hauling Cost Savings 85, 000
Gas saved in not heating Digester 32, 00p
Total O&M Cost Savings $301, 000
On the other hand, when composting is used, the new O&M
costs realized can be summarized as follows:
Operation Costs
Labor $184, 000
Fuel 4 , 700
Utilities 43 , 000
Polymer 46 , 500
Equipment Replacement 19, 300
Maintenance Costs
Loaders and dump trucks 4 , 000
Composting equipment 9 , 000
Total O&M Costs $310 , 500 ,
i
48 513e41---
G' ,e1
C. Revenues
The principal source of revenue for operation of the was-
tewater treatment plant and solids handling facilities is
user charges. Other revenue sources include construction
inspection fees , Industrial Pre-Treatment charges ,
laboratory testing fees, and Industrial Sewer Surcharges .
The following is a summary o£ 1989 actual and 1990 & 1991
budgeted operating revenue:
1989 1990 1991
Actual Budget Budget Est.
OPERATING REVENUE
Sales $3 , 474, 648 $3 , 621, 339 $3 , 693 ,766
Construction Inspection 1, 834 1,200 1, 224
Industrial Pre-Treatment 12 , 442 7 , 000 7, 140
Laboratory Testing Fees 9 , 986 8, 000 8 , 160
Industrial Sewer Surcharge 72, 942 80, 000 81, 600
TOTAL OPERATING REVENUE $3 , 571, 852 $3 , 717 , 539 $3 ,791, 890
The City has already implemented a user charge system to
provide for the operation and maintenance of the solids han-
dling facilities.
D. Project Costs
A summary of the project capital costs is as follows:
( In-Plant Solids Handling Facilities $1, 250, 000
Composting Facilities 2 , 260, 000
Land Acquisition 121, 000
Professional Engineer
Construction Phase 298 ,922
Start-up & Operations Phase 80, 964
Contingencies 56, 664
Total Construction Costs $4 , 067, 550
E. Funding Sources
Project capital cost is being funded from two sources. The
first source is an EPA 201 Program construction grant for
innovative and alternative technology. The remaining cost
will be paid by the City from the Plant Operations Fund.
F. Budget Projection
Operation of the wastewater treatment plant and the new
solids handling facilities is funded from a single was-
tewater treatment facility budget. The following Table VII-
I shows the 1989 budget and projected budgets for 1990 and
1991 . For the 1990 and 1991 budgets , two columns are
provided. One shows the wastewater treatment plant budget
( and the other shows the solids handling project facilities.
When these two columns are added together, the total was-
tewater treatment budget is obtained.
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I
AERATED STATIC PILE COMPOSTING
OF WASTEWATER SLUDGE
FINAL REPORT of a pilot-scale research project conducted
at Longmont, Colorado from 1984 to 1987 .
JoAnn Silverstein
Assistant Professor
i Department of Civil, Environmental and Architectural Engineering
University of Colorado at Boulder
March 1, 1988
VCOSa
i
PROJECT SUMMARY
.1 From June 1984 through August 1986 a pilot-scale aerated static
pile sludge composting operation was conducted at the Longmont
Wastewater Treatment Plant. The pilot study was carried out by
graduate students and faculty from the environmental engineering
-I program at the University of Colorado. Assisting them were many
people from the City of Longmont: Messrs. Howard Delaney, Super-
intendent of the Wastewater Treatment Plant; Grant Grover and
Frank Huffman, plant operators; Steve Martinez, Keith Kvam and
Bart Hawley, maintenance personnel; Ms. Anne Noble, project
engineer; Mr. Arden Wallum, the director of water and wastewater
treatment; and the City utilities director, Mr. Dave Plumb. The
participation of Longmont personnel in the work was essential;
furthermore it demonstrated the effectiveness of the cooperative
effort between a municipal service agency and a university.
j During the test period, we composted 1.5% of the sludge generated
i by the Longmont Wastewater Treatment Plant in two-34, 000 pound
(approximately 650 cubic feet) compost piles. Aerated static pile
characteristics and performance obtained by us are discussed in
this report. Perhaps the most interesting result of our work was
the development of a unique aerated static pile process, using
only recycled compost for bulking material, in which 87% of the
1 sludge input is degraded or evaporated. Other aspects of the
aerated static pile compost methods tested by us are reported
below.
I
I
ef,.At'a
i
TABLE OF CONTENTS
LONGMONT WASTEWATER TREATMENT PLANT 4
COMPOST PROJECT GOALS 5
AERATED STATIC PILE COMPOSTING 7
LONGONT AERATED STATIC PILE COMPOST PROCESS 9
LONGMONT COMPOST PROCESS PERFORMANCE 15
AERATION AND BLOWER OPERATION 21
- COMPOST PILE CORE MIXING 23
EQUIPMENT 25
IINSTRUMENTS 27
TRANSPORT 29
1 COMPOST PROCESS SCALE-UP 30
1l REFERENCES 31
I
I
i
nee92
i
LONGMONT WASTEWATER TREATMENT PLANT
1
The City of Longmont operates a biological wastewater treatment
process. A combination of trickling filters and rotating biologi-
cal contactors are used to treat wastewater for approximately
50, 000 residents and industries. The climate of the Longmont area
is relatively dry and temperate, with ambient air temperatures
)f ranging from -11 to +32 C. Aerated static pile composting of
sludge was one treatment process that was studied by the City; in
this report of the three-year study, project goals, a description
of the aerated compost piles tested, performance results, recom-
mended blower and pile mixing operations, recommended equipment
I and instruments, sludge transport and scale-up considerations are
discussed. The recommendations are based on the experimental
jresults discussed in detail in the three masters theses of Ms.
Rita Klees (1986) , Mr. Jim McDavid (1986) and Ms. Mary Richardson
(1987) , graduate students at the University of Colorado super-
vised by Dr. J. Silverstein. A report on sludge transport has
been made by Dr. Ali Touran (1986) ; and a summary of early
results for 1984 has been given to you by Dr. J. Silverstein
(1985) . The theses and earlier reports contain important detailed
information on pile performance and operations. This report is a
summary of those results that we think are useful in designing a
scaled-up aerated static pile compost operation and of the pilot-
scale work that was done by the University of Colorado personnel .
I
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-4-
equipment, and two operations sequences for blower
operation. The use of static piles means no mechanical
1 operations required during the compost period.
4. LOWEST COST
We tried to minimize unit process construction and
operations costs as compared with costs for alternate
processes.
5. RISES
Minimizing the amount of end product and a high degree of
compliance with State Sludge Regulations allowed us to
I develop a process which proposed minimal future risks:
I1 financial risks to the City and health risks to operators
and citizens in proximity to the sludge disposal site.
-6-
COMPOST PROJECT GOALS
1 From 1984 through 1986 a cooperative research project was done by
faculty and graduate students at the University of Colorado and
staff from the City of Longmont Wastewater Treatment Plant and
i Service Center. The compost process developed to treat the sludge
had five goals:
1. SLUDGE REDUCTION
' The volume and mass of sludge material requiring
disposal was to be reduced as much as possible, i.e. ,
the end product from the compost process was
minimized. Because of the variations in ambient temperature
and humidity at Longmont, seasonal evaluations of compost
performance also were important in sludge reduction
by the composting process.
2. COMPLIANCE WITH STATE REGULATIONS
The Colorado Department of Health (1985) enforces four
regulations for disposal of wastewater sludge by
composting:
a. Volatile solids reduction [in sludge] greater
than 38% ;
b. Volatile solids content [in compost end product]
less than 65%;
c. Total of sludge composting and curing time at least
equal to 80 days;
d. Compost maintained at 40 C for 5 days AND for 4
hours during this period, compost temperature
greater than 55 C.
By law, a sludge compost process must meet at least one
of the above regulations. We tried to develop a process
which met all four, to increase process reliability.
3. OPERATIONS
The aerated static pile process developed for Longmont
was relatively easy to operate and control; we
employed digital programmable timers, unspecialized
C CP,°any
-5-
,Ar k
FIGURES AND TABLES
1 FIGURE 1: TYPICAL AERATED STATIC PILE 8
IFIGURE 2: LONGMONT COMPOST MATERIALS FLOW . . . . 11
TABLE 1: LONGMONT SLUDGE CHARACTERISTICS . . . . 12
TABLE 2 : COMPOST REMOVAL OF SLUDGE MASS,
WATER AND ORGANICS 18
TABLE 3 : COMPOST PILE TEMPERATURES 19
TABLE 4: HEAVY METALS 20
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IAERATED STATIC PILE COMPOST PROCESS
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AERATED STATIC PILE COMPOSTING
lThe aerated static pile compost process for treating sludge was
I developed in part by Epstein and his coworkers at the Beltsville
f Agricultural Research Station (1976) . The process has been
described in detail by Finstein et al. (1980) and the EPA's
Process Design Manual: Sludge Treatment and Disposal (1979) . The
Icomposting process itself, while very old, has been used for
wastewater sludge treatment only within the last 15 years, as can
be seen from the dates of the references.
IIn aerated static pile composting, sludge is mixed with a bulking
agent to form a pile CORE. The CORE is laid over a BED containing
an air distribution system and then covered, usually with a COVER
of the bulking material used in the CORE mixture. The pile,
consisting of BED, CORE and COVER, remains in place for some
� period, during which compressed air is mechanically distributed
lthrough the pile. As a result of microbiological activity in the
pile, organic solids (volatile solids) in the sludge are
destroyed and the pile temperature is raised. Sludge moisture is
removed at the same time by a combination of active and passive
airflow through the static pile. A sketch of a cross section of a
typical aerated static pile used in the Longmont pilot study
project is shown in Figure 1. The end product from aerated static
pile composting is material that is drier, biologically more
inert, reduced in volume and with fewer pathogens than the ini-
tial sludge (U.S.E.P.A. , 1979) .
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LONGMONT AERATED STATIC PILE COMPOST PROCESS
Figure 2 is a sketch of the aerated static pile process developed
during the experiments at Longmont, Colorado. The sludge used in
each CORE mixture was undigested (raw) and dewatered using a belt
press. Average characteristics of the sludge are given in Table
1. It is especially interesting that sludge characteristics did
not vary significantly or in any detectable pattern throughout
the three-year study period. This is an important characteristic
'of the sludge dewatering process used at the Longmont Treatment
Plant.
lA major difference between this process and others was the use of
only finished compost (recycle) as the bulking agent in the CORE
mix, BED and COVER. As Figure 2 shows, the recycle material was
i
used directly in the next pile built. A list of compost pile
characteristics follows; some these values are optima which were
found over three years of research, e.g. , ratios and pile height,
and are designated "O" ; other are ranges of values used all of
which produced efficient compost performance, e.g. , initial
moisture content in the CORE, and are designated "R" ; others are
constraints built into the Longmont pilot project, e.g. , cover
and mixing bed facilities, designated "C" . The extensive experi-
ments that were done on process parameters designated "O" and "R"
are discussed in the theses or R. Klees (1986) and M. Richardson
(1987) and a special report by R. Klees (1987) . Project con-
straints and recommendation for pile weather protection are
discussed at the end of this section. The two operational
-9- Ci h ��y
C'0. 2 >
parameters, pile aeration and mixing, are covered separately in
the two sections following this one.
1 Average pilot-scale compost pile mass, 34,200 lbs, was important
1 for our calculations of pile performance; however, as is dis-
cussed in the "SCALE-UP" Section of this report, total pile mass
l and volume are easily increased as long as aeration system
1 capacity is sufficient.
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TABLE 1: LONGMONT SLUDGE CHARACTERISTICS
ll PARAMETER VALUE
I
JSOURCE UNDIGESTED: 60% PRIMARY SLUDGE
- 40% BIOFILM SOLIDS
TREATMENT BELT-PRESS DEWATERED
AVERAGE MOISTURE CONTENT 75$
AVERAGE VOLATILE SOLIDS CONTENT 72%
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-12-
The following, then, is a list of compost pile
characteristics that can be adopted directly to full-scale
operations.
1. Total aerated static pile PERIOD: 21 - 45 days (R)
2 . RATIO SLUDGE/RECYCLE in CORE: 1/1 (volume and wet
mass) (O)
3 . AMOUNT OF SLUDGE in the entire compost pile:
l - 25 to 35% (wet mass) (R)
4 . BED DEPTH: 8 - 12 inches (R)
l5. COVER DEPTH: 8 - 12 inches (R)
6. PILE HEIGHT: 4. 0 feet (O)
7 . PILE WIDTH: 12 feet (C)
8 . PILE LENGTH: 20 feet (C)
9. INITIAL CORE MOISTURE content: 35 to 61% (R)
10. Pile TEMPERATURE for best volatile solids degradation:
40 - 50 C (O)
11. Piles COVERED and UNCOVERED but without walls (R)
12. CORE MIXING BED paved and uncovered (C)
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1 The constraint on pile width was a result of the test air dis-
tribution pipe configuration. One four-inch diameter PVC pipe
with three 3/8-inch air holes every four inches was used for
J l every 6 feet of pile base width. Compost pile length was limited
only by the size of the area reserved for pilot-scale operations.
The pile shelter, a shed roof approximately 6 feet above the
piles, was built to protect the piles from rain and snowfall.
lBecause the test piles had to be built close to the edge of the
area covered by the shed roof, snow and ice did blow onto one
1
edge of the piles.
1 The open sides of the pile shelter offered the advantage of
lincreased moisture removal; evidence for this came when test
piles were built in an enclosed box which protected the compost
from rain and snow, but allowed for the accumulation of excess
l sludge moisture. Roof protection of the piles was improved by
I addition of roof drainage of melting snow. Experiments comparing
l performance of piles operated without protection and piles built
under the shed roof did not produce results indicating that one
or the other system was superior. As a result, the more conserva-
tive roof system is not recommended especially as it sig-
nificantly increases the cost of the composting process.
The second operating constraint, an open mixing bed, was found by
us to be a disadvantage in the colder months. We observed ice
balls in the CORE mix that were the result of an unprotected
mixing area. We recommend, contrary to the pilot-process con-
straint, that the mixing bed be covered.
-14-
LONGMONT COMPOST PROCESS PERFORMANCE
Aerated static pile performance was measured as a combination of
sludge moisture removal, volatile solids destruction, sludge mass
and volume reduction, sludge temperature elevation and metals
concentration. Except where noted, experimental results are
l averages of 19 months of experimental compost operation (37
I piles) operated from January 1985 to August 1986 by R. Klees and
lM. Richardson under the direction of J. Silverstein. In Table 2,
the removal of sludge water and organics, and sludge mass reduc-
tion are presented. Table 3 summarizes temperature data, and
J Table 4, the fate of heavy metals.
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Combining the sludge characterization information from Table 1
l with the process performance data in this section (Tables 2 - 4) ,
J we have made the following general conclusions about the perfor-
mance of the Longmont aerated static pile process.
1. In the average pile detention period of 26 days, sludge
moisture was reduced from 76 to 35%, a reduction of more
than 50%.
2 . In the same period, volatile solids in the sludge were
reduced from 73 to 33%, a reduction of more than 50%.
- Process performance easily met the regulatory criteria of
more than 38% sludge volatile solids reduction, and
less than 65% volatile solids content in the composted
material. The most significant volatile solids reduction
I occurs when pile temperatures are less than 50 C, i.e. ,
the high pile temperatures recommended for pathogen
destruction were found to be too high for efficient
1 microbiological activity associated with degradation
or sludge organics.
3 . Two-thirds of the static piles attained an average
temperature of 40 C for five days and 55 C for four hours.
Of the 37 test piles built in 19 months, seven did not
reach 40 C for five days (using the average of 12
temperature measuring points in the pile) , and 13 did not
meet the 55 C criterion of the State of Colorado. The most
difficult months to achieve high temperatures in the piles
were January, February, and March, the coldest months of
the year. However, because the contents of these piles
were immediately recycled into subsequent static piles as
bulking agent, the sludge material eventually was heated
to standard temperature associated with pathogen
destruction. The use of recycled compost for bulking agent
seemed to result in a slower temperature rise in the piles.
This effect has been discussed in detail by Klees and
Silverstein (1986) and is discussed more extensively in
this report later in the "MIXING" section.
4 . Of 190 wet tons (382, 000 lbs) of sludge composted in 19
months, 24 wet tons (48, 000 lbs) of end product were
produced and disposed of in the Longmont Sanitary Landfill.
That is a total reduction of 87% of the initial sludge
mass.
5. Pile detention time, defined as pile mass*pile period/
input (sludge) mass, was 86 days; solids retention time,
defined as pile mass*pile period/end product mass, was
474 days. The latter number is an estimate of the length
of time solids remained on the treatment site, and well
exceeds the State of Colorado minimum criterion of 80
days.
6. Heavy metals are concentrated in the composting process
by a factor of more than three. This poses a
problem for Longmont for only two metals, copper and zinc,
both of which exceed the Class I concentrations recommended
by the State for food crop application of sludge treatment
end products. However, because the compost end product is
disposed of in a sanitary landfill, and not sold or
distributed to gardeners or farmers, copper and zinc
concentrations in the end product that fell into Class II
of the State sludge classification system were found to
be acceptable. Certainly maintenance of the lowest possible
inputs of heavy metals is a desirable goal of the city's
industrial pretreatment system.
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TABLE 2: REMOVAL OF SLUDGE MASS, VOLATILE SOLIDS, WATER
PARAMETER REMOVAL*
MASS1 87$
VOLATILE SOLIDS2 55$
WATER2 54$
* Average of data from 9/84 to 8/86
1 Over two years, 9/84 - 8/86
2 Over 28 day composting pile period
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TABLE 3: COMPOST PILE TEMPERATURES
TEMPERATURE CHARACTERISTIC FREQUENCY/VALUE
> 40 C FOR 5 DAYS 81%*
> 55 C FOR 4 HOURS 65%*
AVERAGE TIME TO 55 C 13 DAYS**
l MAXIMUM VOLATILES REDUCTION 37 < TEMPERATURE < 45 C
1
* PILE CORE AVERAGE OF 6 POINTS, 37 PILES
** AVERAGE 6 POINTS, OF 11 PILES
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ITABLE 4: HEAVY METALS CONCENTRATIONS IN FEBRUARY 1986
1 MATERIAL METALS (mg/kg dry weight)
Cu Cd Pb Ni Zn Cr Ag
I
SLUDGE 376 6 124 37 613 33 14
ICORE 764 7 201 59 717 84 23
COVER 787 8 222 64 733 96 30
1 CURING 913 10 245 65 1274 * *
1
* not measured
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PAC0824
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I COMPOST PILE OPERATIONS
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` AERATION AND BLOWER OPERATION
l
It was found that the aerated static pile compost period could be
divided into two fairly distinct parts: a COMPOSTING PERIOD from
day 1 to day 14, and a DRYING PERIOD from day 15 to day 28. In
measurements made April through August 1986, the airflow rate
provided by the 1/3 HP blowers was at least 667 standard cubic
feet per minute (SCFM) . During the COMPOST PERIOD, the range of
airflow rates was 4.3 to 43 .8 SCFM/dry ton; during DRYING
PERIODS, the range was 20.8 to 102 .4 SCFM/dry ton (Piles 41 -
I48) . In the pile CORE, ambient oxygen concentrations measured
during 1985 (Piles 35 - 38) ranged from 7 to 20% of total air
,.,.� mass; in the COVER, measurements in the same piles ranged from 10
to 20% oxygen.
( 092A
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1 The following are recommendations based on experimental blower
operation during two years of pilot tests:
l 1. Blowers should push air into the piles both during COMPOST
l and DRYING periods.
I This mode of aeration results in better retention of
heat, more even distribution of heat and better advection
of moisture out of the pile. Also compost solids and water
do not accumulate in the pipes or corrode blower parts.
l This mode of aeration was found to produce no odors.
` 2. During the COMPOST period, the blowers should be ON 10
minutes followed by OFF 10 minutes, 24 hours/day.
This mode of aeration results in a rapid rise in pile
temperature and good removal of compost volatile solids.
3 . During the DRYING period, the blowers should be ON 30
minutes followed by OFF 30 minutes, 24 hours/day.
l This mode of aeration results in efficient reduction
of compost moisture and volatile solids.
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COMPOST PILE CORE MIXING
Numerous experiments were done on the variables sludge/recycle
mass ratio, initial pile moisture content, and mechanical method
of mixing the pile CORE. The optimum value for sludge/recycle
1 ratio (1/1) has been given. It should be noted that larger ratios
(sludge fractions) were composted successfully, but odor problems
were experienced. Because odors are an important concern both for
the people who must work around the piles and nearby residents,
odor-causing ratios of sludge/recycle mass in the pile CORE have
not been considered. Initial CORE moisture contents ranging from
35 to 61% were composted successfully, and statistical analyses
of test results verified that initial CORE moisture content
within the ranges tested did not alter the effectiveness of the
aerated static pile compost process. It should be noted that in
1984 a very wet (>80% initial moisture content) pile did not get
hot. We added water to this CORE mixture; certainly that is a
procedure we do not recommend, and from our experience with this
pile, very high initial moisture content is undesirable.
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t For mixing the CORE with the purpose of making a uniform com-
1
J posite of sludge and recycle material with a fairly uniform
particle size of less than 3 inches in diameter, we recommend:
1. An auger-type mixer be used.
It is not necessary to purchase an expensive "Scarab"
type mixer; in tests done in 1986, this mixing did not enhance
compost performance. We used a "Brown Bear" type auger
l which can be installed in an ordinary front-end loader
t bucket.
- 2 . A front-end loader bucket does not provide satisfactory
mixing.
We found uneven particle sizes and nonuniform mxing
I of sludge and recycle material, with lower pile
temperatures and volatile solids reduction when we used
a front-end loader to mix the pile core.
i 3 . Finished compost pile material should be mixed into
the new pile CORE on the same day.
Especially in winter, recycle material left overnight
(even covered with a tarp) gets very cold; some winter
days, ice balls formed in the pile core, slowing subsequent
heating in the pile.
4 . Auger mixing requires that the sludge and recycle
material be spread out to a maximum thickness of
6 inches on the mixing bed.
Greater mixing depths produced inefficient mixing. This
I requirement can be satisfied by providing a mixing bed
of sufficient size. Odors during mixing can be curtailed
by enclosing the mixing area.
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EQUIPMENT
1
The success of aerated static pile composting depends on three
1 large pieces of equipment in addition to the blowers and mixers
described. They are the sludge dewatering, transport, and pile
1 construction equipment.
1 SLUDGE DEWATERING
IAn efficient belt-press was available to us throughout the three
year pilot test period. This belt-press produced a raw sludge
1 cake of 24 .4% solids concentration with great consistency; the
standard deviation of the mean sludge solids concentration was
,) less than 3% of the mean value. Using the present belt-press
about 50% of the plant sludge (2002 estimate) can be dewatered
for composting. Composting 100% of the sludge would require
purchase of a similar press, or demonstration that another
dewatering process performed as well. We cannot overemphasize the
importance of the dewatering process in sludge composting. Time
and motion studies conducted by us in 1986 showed that the belt-
1 press dewatering was the critical factor that determined time
1 required in building a compost pile.
i
SLUDGE AND COMPOST TRANSPORT
Both raw sludge and finished compost were transported in two
five-cubic-yard dump trucks made available to the project. The
solids content of sludge and compost are sufficient for this
method of transport, and too great for pumping. If necessary,
compost materials can be moved by conveyor belt; that was not
I
1 tried during our experiments, but we were assured of this option
l by an experienced construction engineer who helped us with re-
search on sludge transportation.
1
COMPOST PILE CONSTRUCTION
Compost piles were built (and torn down) using a front-end loader
loaned to the Wastewater Treatment Plant by the Street Depart-
ment. We were able to build and tear down piles rapidly (in less
than 30 minutes for a 34,200 lb pile) with this vehicle, and
recommend its purchase for continuous usage in a scaled-up ver-
sion of the compost process.
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INSTRUMENTS
I
We recommend the purchase of digital programmable timers to
Icontrol blower operation and automated pile temperature measure-
ment and temperature data logging. These instruments were used
successfully by us in this research project. Our experience was
-I that operators could use both these instruments and that they
provided satisfactory control and monitoring of the composting
Iprocess.
ICOMPOST TEMPERATURE
Static pile temperature was found by us to be the most easily
Imeasureable parameter indicating successful process performance.
In addition, pile temperature is one of the four criteria used by
the State of Colorado to measure satisfactory composting of
sludge. For this reason we are recommending relatively careful
' measurement of pile temperatures. The EPA (1979) recommends use
use of a daily temperature which is the average value of measure-
ments taken at four locations in the static pile. In these pilot
studies we used an average of ten measurements to characterize
pile temperature. Temperature was initially measured manually one
to three times per day; in 1985 an automated temperature logger
was connected to ten thermocouples in each pile. The temperature
' at each of the ten points was recorded every two hours. We recom-
mend that a fraction of the piles built in a large-scale compost-
ing operation be monitored for temperature at the four points
recommended by the EPA. If temperature data are collected from
one 34 , 000 pound compost mass built every two days at four points
J in that mass, we think an adequate characterization of compost
operating temperature profiles can be obtained.
Some investigators have suggested use of pile . temperature to
control the blower system. Such a feedback control system seems
to us to be an unnecessary expense. We have found satisfactory
1 pile temperature profiles if blowers are operated during the
COMPOST and DRYING periods on the fixed schedule recommended
above. Temperature monitoring can verify this in future opera-
i tion.
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TRANSPORT
1
Composting costs are not as sensitive to transportation as land
Idisposal of digested sludge. In a study we performed in 1986,
composting construction time (and cost) was most sensitive to
Idewatering operations. Transport of dewatered sludge to a compost
Isite away from the waste treatment plant increases the transport
costs, but varying an estimated transport distance up to five
Imiles to the Longmont landfill did not significantly alter pile
construction time. If the composting site is a long distance from
Ithe treatment plant, the computer simulation program developed
for studying composting times can be rerun to test it transport
Ibecomes a significant factor is compost cost.
1
Ft 09,2^'S
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1 COMPOST PROCESS SCALE-UP
The three year study that was managed by faculty and students of
jthe environmental engineering program of the Civil, Environmental
and Architectural Engineering Department of the University of
Colorado has provided much information for the design of a full-
scale aerated static pile compost process. Because large pilot-
scale tests were made from 1984 to 1986, scale-up of pilot test
composting operations mostly requires multiplication of values
for pile length and width, blower capacity, equipment and instru-
ments required. Data from the pilot tests on blower operation,
mixing and aerated static pile compost performance can be applied
1 directly to predictions of full-scale compost performance. The
design engineer should be able to develop an aerated static pile
design by calculating the area required for full-scale mixing and
for the piles themselves, the cover required for the mixing area,
and the amount of recommended equipment for scaled-up operations.
The following are items that we think need to be determined for
scale-up of the pilot-project results:
f 1. Compost pile site
2. Mixing bed/shelter and equipment
3. Pile shelter
4. Full-scale pile configuration (length and width)
+ 5. Aeration equipment
J 6. Use of the product material for landfill cell cover
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I
REFERENCES
1
Colorado Department of Health; (1985) Domestic Sewage Sludge
Disposal Regulations; Denver, CO.
1
Epstein, E. et al. ; (1976) "A forced aeration system for
composting wastewater sludge;" J. Water Pollut. Control Fed. ;
1 V. 48:4 ; p. 688.
1 Finstein, M. et al. ; (1980) "Sludge Composting and Utilization:
A Rational Approach to Process Control;" Final Report; Rutgers
University; New Brunswick, NJ.
I
Klees, R. and Silverstein, J. (1986) "Aerated Static Pile
Composting of Municipal Sludge;" Proc. of the ASCE National
1
Conference on Environmental Engineering; Cincinnati, OH.
1 U.S.E.P.A. ; (1979) Sludge Treatment and Disposal ; Process
Design Manual ; Washington, DC.
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PILOT RESULTS
c
INDUCED AERATION WINDROW
COMPOSTING OF RAW SLUDGES
HE Clark County Sanitation Dis- evaluate the feasibility of using the current
trict in Las Vegas, Nevada oper- / system with other sludge management alter-
ates a 40 mgd biological wastewa- PllOt-scale natives and, very importantly, to examine
ter treatment facility that utilizes the potential for the beneficial use of a sludge
screening,primary and secondary ` end product that could be used either as a
clarifiers and single stage trick- COmpO$ting of soil amendment or as fill material in the arid
ling filters. Under construction at desert environment where alkaline and ce-
chemically
the present time is an 18.5 mgd primary mented sandstone soils abound.
plant addition. The effluent from the pri- conditioned and The consultant's report included the rec-
mary plant will be blended with the second- ommendation that the District proceed with
ary plant effluent that is currently conveyed dewatered raw plans for anaerobic digesters and a full-scale
to the 90 mgd advanced wastewater treat- windrow composting facility for digested
\ ment(AWT) plant, a physical-chemical phos- sludges secondary sludge. It was further recom-
phorus removal facility. The AWT plant !n Car mended that the design of a full-scale facility
utilizes lime rapid mix, flocculation,clarifica- County Nevada be preceded by a small-scale windrow com-
lion, pH adjustment, dual media filtration, / posting demonstration project utilizing raw
post aeration and post chlorination. found an organic sludges, for the purpose of answer-
The Sanitation District has experienced ing questions concerning odor potential and
continued difficulty with the disposal of raw anaerobic digestion product quality. Substantial capital cost sav-
sludges generated from primary and second- b ings would be realized if the construction of
ary wastewater treatment plant processes step is not anaerobic digesters could be eliminated from
since the early 1960s. The District's sludge the process train.
handling practices have included the use of necessary. The decision to evaluate induced aeration
anaerobic digesters with sludge drying beds, windrow composting was predicated on the
hauling of raw sludges to a remote site for mid to evaluate its effectiveness in control-
land disposal, wet air oxidation, vacuum fil- ling internal temperatures,ventilation,odors
tration and incineration of the filter cake, James Wren Jarvis and the rate of biological stabilization. Path-
and raw sludge injection into the sub-soil.To- ogenic bacteria destruction, trace metal con-
day, the process method is the plate and centrations and the ability to compost lime
frame press with final disposal of the filter stabilized raw sludges were also of signifi-
cake to a sanitary landfill. cance in terms of producing a material that
Realizing that a fully comprehensive would be stable and could readily be used as
sludge management plan had never been fill or as a soil amendment in the landscaping
prepared, the District retained the services and horticultural industry.
of a consultant to prepare one. The purpose
of the consultant study was to investigate a FACILITY DESCRIPTION
long-range, cost-effective and reliable A 7,200 square foot blacktopped area adja- .
method of handling raw wastewater cent to the AWT plant solids handling build-
treatment plant sludges. The study was ing was selected as the composting site be-
prompted by several reasons beyond the cause of its proximity to the filter cake
need for a comprehensive plan, the foremost unloading area and to the headworks to
being the potential liability associated with which compost filtrate could be returned. In
C the long-term landfilling of raw sludge,ques- addition, large open areas were available for
Lions about the long-term reliability of the the storage of bulking material and for cur-
existing landfill operation and concerns with ing of the compost material.
the forthcoming federal sludge management Aeration system: The existing blacktop
programs and regulations. surface was cut and excavations made for
In addition, there appeared to be a need to the construction of the two-parallel-Wee-
25
ter (40 foot) long concrete ar cot/. A 1.he hL0T PROJECT RESULTS
cm thick perforated steel plate laced a plastic Seven windrow cycles were completed dur-
channels, above which wasp nod. The first was initiated
mesh support, fine mesh screen overlaid ends
ing the study 1986, and the final cycle was
of each
(3 inches)o silica sand.The west ends on March 25, 1986. A brief de-
east is as follows:
of each channel were blanked off end on the concluded on October 2 to nature
east ends c cm(8 inch)diameter PVC pipes scCycle N1:This waption of the s introductory operators
interconnected the channels to the blower as- Cy set up cle to familiarize the ope
chansembnel
i A cutaway section of the aeration with the mechanics of the operation and to
channel is shown in Figure 1. protocol for collection and han-
The blower assembly vault was con- establishamples.Woodchip bulking particles
strutted below ground level with reinforced citingwere compost mixture.
concrete floor base and sides (see Figure 2 were used in the come
blower configuration). The pipe connecting Cycle conditioned
N2: Raw sludges were con condidi ferric
the aeration channel to a 208 liter(55 gallon) with 20 percent lime and 5 percent
ferric
A
airtight steel drum installed as the collector chloride and
compost mixture wadewatered on filter s prepared
sump and air cushion chamber,was set to a 41 percent grade of 2.1 cm per meter(114 inch per foot)to with sawdust as the bulking particle. Blow-
allow for condensate drainage- And air flow ers were set to draw air downwards through
damper and pitot tube arrangement con- the windrows son 10 air flow m Wminute on-60 indrow
offf
netted differentially to a manometer was in- cycles.
stalled ahead of the collector sump. Air ve- Nl caused severe odor conditions to occur.In-
locity setting were established off the creased
sTemperature rd the con in i ion Witt i 24
manometer readings.
IMMINISMISMISII
FIGURE 4
FIGURE 1 Blower configuration Ain To ODOR
Aeration channel (Cutaway section) SCRUBBER
BLOW
XHAUST
COMPOST
WINDROW
BLOWER INTAKE
CC
OR WOST MATERIAL
/ TO MANOMETERII.III ,Q,ii,`vi
SANG 5.M C. rumumuuu. .��'ui III ■'I I '
( EVE LIESN SCREEN / � ,
idir
MSTIC YESN SUMCAT
STEEL PLAT
STEEL PLATE / - AERATION AIR VELOCITYLE AGNATE
_ CHANNEL PROBE CONDENSATE.
CONCRETE AERATION TROWN DAMPER
� v
Ii The final compost material
Blower and controls: Each windrow was haven erratically. H of id7. with
equipped ble of mmoTving 34m 1(1200 scfm assembly
The centratiun of 79 percentand a pH solids con-
controls for the blowers operated off signals <1.0 MPN total coliform, fecal coliform and
to a programmable logic controller which Salmonella present. D/T odor levels were
controlled the blowers either on time cycles minimal.
Cycle N3: In Windrow N1 raw dewatered
or temperature and tom ui ment: sludges were mixed with recycle compost
Odor control and composting a equipment: from Cycle 1 while Windrow N2 was a mix-
monitor nitor ilCheney Shr threshold
levels was used to
cled compost
monitor dilution to tmpling stations around d from Cycle 2,sludge and Windrow N2. The initentroand
tal
at five established.27 meter
� the study site. A 4.27 meter(14 foot) Scarab solids ocent respeche t/elywere 4 pe
composting machine was used for the turn- 38.3 were were set the same as for Cycle 2.
ing he windrows.
The failing h is a breakdown of the costs Blowers
of 34melmin. were installed to handle
r blowers with a maximum ca-
higher peak aeration rates when needed.
of installing the compost project facilities: temperature conditions in Windrow N1 were
$ 5,98$ erratic, and the windrow was drove/11 w re
Construction materials 2,204 w was levels failed to
Blower assembly 1,256 ter day 25 when temperature CFA
�ie'riesasupplies 13,002 recover to above 55°C. Windrow 12 was
`'ies and benefits completed satisfactorily with a solids con- A-.'
$22,447 centration of 88.2 percent, pH of 7.6 and no
.er rental was$1,400 per month. microorganisms present. Odor levels were
Allan,1988 49
__--
nonexistent from day 10 to the end of the cy- els were reduced to 2 D/T. Product quality in
cle. Windrow #2 was acceptable.
Cycle #4: An attempt was made to com- Cycle #6: Raw dewatered sludges were
post (by windrow) a 30 percent raw dewa- again conditioned with the liquid flocculant
`bred sludge without a bulking amendment. but at the higher dosage rate of 50 Kg per
.temperatures in both windrows failed to in- dry tonne(100 pounds/dry ton). In addition,
crease above 30°C, and even though the to- 5 percent ferric chloride was added for both
tal solids readings of 60 percent indicated a release of bound water as well as odor sup-
drying effect occurring in the windrows, pression. The 32 percent cake was mixed
there appeared to be very little organic de- with sawdust to form a 59 percent mixture in
composition taking place. Windrow #1. The 32 percent filter cake was I ;
The pH levels remained above 11.0 until combined with woodchip to form a 57 per-
day 20 when some drop in pH occurred in cent mixture in Windrow#2.Blower settings
both windrows. Microorganism levels were were 1.0 and 0.85nDmin.respectively on a 10
initially low and on termination of the cycles minute on-60 minute off cycle. Temperature
on day 21, very little change was noted. elevations were very rapid and sustained
Cycle #5: Raw dewatered sludges were above 55°C till the end of the cycle. 'Ibtal
mixed with a high molecular weight long solids concentrations of the final compost
chain polymer at a dosage rate of 40Kg/dry were above 85 percent with a final pH of 8.1
tonne (80 pounds per dry ton). The sludges in Windrow #1. Inactivation of total coli ,
with total solids concentrations of 43 percent form, fecal coliform and Salmonella was ac- "
were blended with sawdust. Blower settings complished in both windrows. Odor levels
were 1.1m3/dry tonne for Windrow NI and were very low throughout the cycle suggest-
- *NV ' i ;
Table 1 # ' . * I
Seamtaty of Initial and Final Compost Cbatactedstics
Valume Bulk Density Percent Solids
r�rr
cu m cu yd Wm m Iblcl Total Volatile pH
Cycle 1 Initial 33.0 43.0 0.48 30.0 36.0 B.5 •' ' 1e�� `Y s
Windrow#1 Final 51.2 8.1 �
Cycle 1 Initial 22.2 29.0 0.59 37.0 31.0 I
.'4ndrow#2 Final 75.1 8.2 "" ••
( cle 2 Initial 33.6 44.0 0.45 28.0 41.0 74.2 9.5 -�
Wind ow Cycler2 #i Initial 26.0 34.0 0.43 27.0 37.1 76.1 10.5 I f III is:i
Windrow#2 Final 0.35 22.0 79.0 67.8 7.8 , I l i I IIf I:I
r i
Cycle 3 Initial 18.4 24.0 0.53 33.0 43.0 47.0 11.0 1 I ,
Windrow#1 Final 9.2 12.0 0.34 21.0 88.0 44.0 7.1 / ; (i 1
Cycle 3 Initial 18.4 24.0 0.56 35.0 38.3 57.4 10.9 I• M*�
Windrow#2 Final 7.9 10.3 0.37 23.0 68.2 53.5 7.6 '� r - �i_
Cycle 4 Initial 23.0 30.0 0.66 41.0 30.9 53.5 11.9 oe
„ 77-f ~ �� ".,1*1 "
Windrow#1 Final 59.8 54.7 9.9 ., - 'i:1 + „ '
Cycle 4 Initial 23.0 30.0 0.66 41.0 29.9 53.1 11.9 /: � x,:g
Windrow#2 Final 52.4 57.9 8.4 lr ' i y{K'i"t
Cycle 5 Initial 34.4 45.0 0.54 34.0 36.0 79.8 8.3 '00-- � .,,t, V .-s
Windrow#1 Final 0.34 21.0 92.4 77.3 7.3 >• # �.'
Cycle 5 Initial 32.1 42.0 0.51 32.0 40.0 76.2 8.0 w .
Windrow#2 Final 0.32 20.0 92.7 77.7 7.0 '
Cycle 6 Initial 39.8 52.0 0.59 37.0 38.0 84.0 6.2
Windrow#1 Final 0.32 20.0 88.0 82.4 8.1 st
Lytle 6 Initial 39.8 52.0 0.56 35.0 38.4 87.0 6.8
Windrow#2 Final 0.38 24.0 85.0 80.8 6.7
Cycle 7 Initial 42.1 55.0 0.51 32.0 37.3 76.0 6.3 A 7,200 square foot blaektopped area
Wndrow#1 Final 0.34 21.0 53.4 75.4 7.4 adjacent to the treatment plant served as
Cycle 7 Initial 42.1 55.0 0.54 34.0 34.0 77.0 7.3 the composting site, with additional area
Windrow#2 Final 0.32 20.0 51.8 76.4 7.1 available for bulking agent storage and '
curing piles.
0.78m'/dry tonne for Windrow #2. ing that the ferric chloride may have ac-
Temperature elevations occurred rapidly counted to some degree in odor control. The
with frequent changes occurring in Wind- compost off both windrownyag-q&moen�l sual-
row #1. Temperature conditions remained ity. a ;‘The .
fairly uniform in Windrow #2 through the Cycle #7: Raw sludges were conditioned
end of the cycle. Final total solids concentra- with the same dosages of polymer and ferric
/ -ins in both windrows were above 92 per- chloride as in Cycle 6. In Windrow #1 the 31
\. .ent with a pH of 7.0 in Windrow #2. Micro- percent sludge combined with the 88 percent
organism inactivation to zero levels occurred recycled compost from Cycle 6 Windrow #1
by the 11th day into the cycle. Odor levels was mixed to a 37.8 percent concentration.
were quite noticeable in the early stages of In Windrow#2 the raw sludge was combined
the cycle so blower cycles were increased to with the 85 percent recycled compost off Cy-
20 minutes on-60 minutes off until odor lev- cle 6 Windrow #2 to a mix concentration of
50 BioCycLE
34 percent.Blower rates were the same as in of sludge balls and resultant poor mixes. No
the previous cycle. Temperature elevation problems were encountered in the cycles
was rapid in both windrows with the higher where sawdust was used as a bulking parti-
levels recorded in Windrow #2. The final de probably due to using drier dewatered
, solids concentration was above 51 percent sludges and thorough mixing techniques.
with a pH of 7.1. Total and fecal coliforms In Cycle 4 of the study, raw dewatered
! concentrations were reduced to <1.0 MPN/ sludges were set up without bulking parti-
g.Odor levels were generally higher than Cy- cles. The cycle was unsuccessful largely due
de 6 so the blower cycles were increased to to a lack of free air space,porosity and struc-
20 minutes on-60 minutes off until odor ley- tural stability in the windrow, resulting pri-
( els decreased to the 2 D/T levels. Compost marily from the plastic characteristics of the
produced from both windrows was of good sludge.
quality. Aeration: Haug' has stated that air must
Table I provides a summary of the initial be supplied for three basic purposes: (1) to
and final compost characteristics for each of satisfy oxygen demands imposed on organic
the seven cycles. decomposition and also for the removal of
carbon dioxide and free ammonia; (2) to re-
REVIEW OF FINDINGS move moisture from the composting mate-
In the early 1970s the Blue Plains plant in rial to provide drying;(3)to remove heat gen-
Washington D.C. attempted windrow com- erated by organic decomposition to control
posting of raw sludge and encountered diffi- process temperatures. The aeration system
culties because of high level of odors. Since used in the study was a separate blower con-
raw sludge generally contains higher levels netted to each windrow. The blowers were
of pathogens than digested sludges, there used to carry the peak demand of air for heat
was concern that some of these organisms removal, and sized sufficiently large to ac-
might survive in the outer layers of the wind- FIGURE 3 commodate the peak aeration rates. Murray
rows where temperatures are lower.The Dis Temperature comparisons et at reported that peak aeration rates of 125
trict study focused on the above mentioned between windrows. to 156 cubic meters per metric dry ton (4,000
concerns with an evaluation of induced aera- to 5,000 cfh/dt)of sludge were sometimes in-
tion windrows as a means of controlling sufficient to keep process temperatures be-
odors and providing air for the aerobic de- ----:i�� low 60°C when composting a raw sludge/
composition of organics. In addition, fre- - woodchip mixture in an aerated static pile.
quent complete turning of windrows pro- I, - j __ In the study windrows, it was necessary to
' vided the assurance that lower temperature i •. / increase peak aeration rates to as high as
( outer layers would be brought to the center ^. 187m'/metric dry ton (6000 cfh/dt) for short
of the windrows where higher internal tem- periods until peak demands for temperature
peratures prevailed. control had passed, which affirms close simi-
Moisture Control and Mixing Ratios: The • ' •• larities in the peak aeration rates for static
importance of moisture control has been — ""°" "` "' pile and raw sludge windrow composting
highlighted in works by Senn' and in the Los techniques.
Angeles Sanitation District studies where it Hay reports on the findings of the Los
has been determined that material with 60 Angeles Sanitation District aeration re-
percent moisture or less developed rapidly el- search project that aeration works best when
evated temperatures. It was further deter- starting total solids exceed 40 percent, and
mined that at higher moisture content the further that sawdust windrows perform bet-
mixtures tended to slump.This was affirmed ter under forced aeration. The Clark County
during the study in Cycle 4 when dewatered project conformed with the above state-
raw sludge windrows set up without bulking ments with the exception that when a wind-
particles slumped to the extent that voids row was initialized with a mix of 35 percent
and free air space were virtually eliminated total solids concentration, it was generally
and temperature elevations did not occur. slower in starting,but the total compost pro-
Mixture ratios in three other cycles were set cess was carried through to successful com-
up with moisture content in the 62 to 65 per- pletion.
cent ranges and these were successfully oper- Temperature: Temperature, one of the
ated, which leads to the conclusion that set- most important composting operational ga-
ting a minimum target moisture content of rameters, is a good indicator of biological ac-
60 percent is conservatively acceptable for tivity within a windrow and also of the prob-
raw sludge windrow composting. able extent of pathogen destruction or
The study utilized four different ap- survival.The U.S.Environmental Protection
proaches to control the moisture content in Agency promulgated the windrow compost-
] the feed substrate. Each was equally effec- ing standard of 55°C for 15 days with a mini-
tive.The four approaches included the use of mum of five turnings. This standard was
recycled compost, a dry amendment (saw- used in the study for monitoring the destruc-
dust), bulking particles (woodchips), and air tion of pathogenic bacteria. It was interest-
drying. ing to note that temperature elevations ap-
Bulking Particles: The primary bulking peered to occur more rapidly in windrows
\. particles used in the study were woodchips prepared by polymer conditioned raw
and sawdust.These were selected because of sludges than they did for the lime and ferric
A�
their porosity and capability to significantly ^S, q a'-= chloride conditioned sludges (see Figure 3).
absorb moisture.Other authors have encoun- e,. Hydrogen!on Concentration: !taw sludges
tered problems with very fine bulking mate- at the District facilities are generally within
riots,such as sawdust,causing the formation a pH range of 6.5 to 7-2 with the addition of
APa11. 1988 51
. ............
20 percent lime and ferric chloride for raw windrow, with a substantial increase in odor
sludge conditioning.The resultant filter cake levels. The damper was opened and blowers
pH ranged between 10.5 and 11.5. Similarly, turned on continuously for 24 hours at its
when long chain high molecular weight poly- maximum aeration capacity before the wind-
mers were used for conditioning, the filter row recovered; and (2) Conditioning of raw
cake pH would be below neutral. Haug' sludges with polymers apparently results in
states that under the above mentioned pH a dewatered filter cake that is quite odorous.
conditions, an initial lag in the composting Aeration rates and duration of blower opera-
rate can be expected, and this was affirmed Lion had to be maintained at an increased
in the study. Eventually the carbon dioxide level until odors were reduced.
and ammonia produced by the slow persis-
tent microbial activity neutralized high or
low pH and overcame the rate limitation. It was concluded from the study that:
Disinfection: Study findings show that to- (1) Raw sludges conditioned with lime and
tal and fecal coliform concentrations of less ferric chloride prior to filter press dewatering
than 1 per gram of material were achieved in can be successfully composted in aerated
all seven cycles. Salmonella, ascaris and as- windrows.
pergillus monitoring was conducted during (2)Raw sludges conditioned with polymers
the study, and it was found that tempera- prior to dewatering tend to produce a more
tures were sustained such that adequate dis- odorous filter cake,which can be successfully
infection occurred. composted with carefully monitored and con-
Odor Control: Las Vegas is a burgeoning trolled aeration rates.
city, and the concomitant encroachment of (3) Frequent turnings are necessary to
bring the cooler outer layers of the windrow
_ in contact with the higher internal tempera-
Compost bed evaluation t�-
(4)Raw dewatered sludges with 30 percent
FILTER PILE total solids content could not be composted
without the addition of a bulking material to
provide free air space, porosity and struc-
tural stability.
(5)Study windrows required peak aeration
BLOWER rates as high as 187m/metric dry ton of
sludge to control peak demands for tempera-
( ture control.
(6) Windrows with initial total solids con-
centrations of 35 percent, although slower in
starting,were ultimately composted success-
ierO D O R fully
DISTRIBUTION (7) When temperatures of 55°C and above
illkth are maintained for 15 days with five turn-
VAULT ings,adequate disinfection is provided to the
compost material.
CONDENSATE (8)Temperature elevations occur more rap-
COLLECTOR idly in polymer conditioned sludges than
lime stabilized sludges.
residential areas upon treatment plant (9) Carbon dioxide and ammonia produc-
boundaries makes the issue of odor control Lion in aerated windrow composting pro-
significant. There are many techniques for duced by slow microbial activity eventually
collecting and reducing odors from windrow neutralizes high or low pH materials in the
operations including the use of natural mate- windrows.
rials. The technique of utilizing compost (10)Natural material beds for odor control
beds was evaluated in the study (see Figure may have an application in remote areas,but
4), but there were limitations with regard to for urban locations the need for mechanical
controls of moisture and temperature, buf- odor scrubbers seems apparent. ■
fering capacity and, most importantly,a gen-
eral lack of engineering data by which sys- James Wren-Jarvis is deputy director of.the
tem performance could be monitored. The Clark County Sanitation District.
above mentioned properties and limitations
may have their application in remote facili- REFERENCES
ties, but with the current sensitivity to odor 1. Senn, C. L., "Dairy Waste Management
issues by the community, it becomes clear Project—Final Report." University of California
that the use of more sophisticated controls Agricultural Extension Service, Public Health
such as mechanical odor scrubbers, must be Foundation of Los Angeles County.(1971).
implemented to reduce composting odors to 2- Haug,Roger Tiro,"Compost Engineering Prin-
a near nonexistent state. ciples and Practices." Ann Arbor Science Pub-
lishers, Inc., Ann Arbor, Mich. (1980).
Scentometer monitoring indicated that 3. Murray, C. M., et al, "Strategies for Aerated
odor levels were not significant with two ex- Pile Systems." Biocycle, Jour n�j pf aW y-
cept ion s: (1) In Cycle 2, the unplanned clos- cling, Vol. '27, No.s, (July 1980 �fl ,,
ing of the air flow damper in Windrow #1 re- 4. Hay,Jonathan C., "Windrow Aeration Study."
salted in no air movement through the JWPCP Research Report.(November 1985).
52 11ioCra.r:
S composting facilities gain ENCLOSURES FOR COMPOST PROJECTS
more operating experience, the
steps necessary to improve
overall performance become
more cleat For example, when
the Beltsville aerated static pile
method was first developed in To coyER
the early 1970s, it was thought that this .
composting method could function well out
in the open,under a variety of climatic condi-
tions.While that basic theory still holds true,
other ®R NOT
other factors—such as location of the facil-
ity—mean that open air composting may not
'
be feasible.As a result, more and more "non-
reactor" composting operations are taking
cover or, in some cases, becoming totally en-
closed. i s- —
The Sussex County,New Jersey Municipal COVER
Utility Authority's composting operation is .i_ t _ ,
a case in point. The 12 dry ton per day ex- 1 j � .
tended static pile facility began operating in I il r .
� ) , ,,i i
July 1984. It was plagued by odor problems
and thus complaints from neighbors(see Bio-
Cycle, April 1987 for a full report). Ulti- +--- ,
mately,operations were suspended in Febru- —,(
ary 1985,until a solution could be found.The Managers of ,,.,,r,., ----,.
primary upgrade was to install a new aera-
tion system that employed positive (forced non-reactorF
air) aeration. The operators also found it es jar
sential to put the compost piles inside of composting ------:. tiSHISS .. c .
buildings.
"We wanted to do everything we could to facilities debate -,;2I"+«. --'AT.•47,t t,sm¢ y`•
keep the rain and snow from affecting the
piles," says Peter Goodman of the Sussex merits of enclosing ro t - "-
County MUA."In addition,the buildings en-
able us to control odors and keep the site components of .. ��.. s v ,_
cleaner, which also gives us more control of • ~ z '^.^«�.
the composting area." their operations. ���,.a \
Five prefabricated steel buildings were ?
constructed to house the compost piles. ;} �r 43
Each building has six totally independent NOtB GOlCIStCI[1 .-;.•,. Y
aeration systems. Air is pulled through the �� 4 Z ,
buildings by two 40,000 cfm exhaust fans lo-
cated in the back of the buildings to elimi-
nate all water vapor released from the piles, components of a composting operation. "Cli- Aerial view of Scranton,
and to dilute the off gases from the compost mate and neighbors and public acceptance is- Pennsylvania project that
process. sues drive facilities to covers," says Richard uses two buildings to ensure
To date, the exhausted air is released into Kuchenrither, a consultant with Black & greater flexibility during
the atmosphere, without scrubbing any Veatch in Denver,Colorado."Covers are very wet weather.
odors that may be present.The MUA is plan- important for process control, especially if a
ning to process that air in the future, even facility is in a climate with lots of precipita-
though the facility only receives several odor tion. There can also be some odor control ef-
complaints per month. The first step, how- feet from enclosing buildings because it pre-
ever, is to replace the fabric doors of the vents wind from blowing across the piles,
buildings with something more permanent. which enable odors to escape. But covers
Recently, an open frame building was con- only capture odors. Then a system must be
strutted for the curing phase of the compost- designed to treat them."
ing process.Total costs for the upgrading,in- A potential drawback to covers,he adds,is
eluding the new buildings, blowers, and that they can shield the piles from the sun,
computerized temperature feedback system retarding the drying effect. A solution is to
were $450,000. install covers with solar panels, which allow
90 to 95 percent of the needed radiation to
COYER-UP DEBATE
get through. This design was used effec-
The most common approach to covering a tively at Denver Metro's aerated windrow
composting operation is to build an open- composting facility.
sided building, i.e. to simply put a roof over In aid climates, covers may be needed to
the area needing cover. Oftentimes, these avoid premature drying due to excessive ex- e , i Te, fi
same structures can be fitted with sidewalls posure to the sun. Black and Veatch, there- .'3>�s' ,
if necessary fore, is considering covers for an aerated
A variety of factors have an impact on a windrow composting facility it is designing
decision to cover and/or enclose all or various for Las Vegas County, Nevada.
34 Bi0C`a3 C
covers and enclosures often boils down Lo
economics—when the costs of enclosing a
non-reactor system begin to approach the
cost of an in-vessel system. "'Chat is very
site-specific," says Kuchenrither. "In the
case of Denver,and in Philadelphia where the
facility has been enlarged, it was less expen-
,_..1,;,,�• ;': sive to put on covers and construct buildings
,�. . than to build an in-vessel system."
.. "' t r i�.i~ While enclosing composting operations is
- not a solution to controlling odors that may
"c ' ''...":4(,:.J.--. ' be generated, New Jersey's Department of
�` '• , r ` ��'� �� F,nvironmental Protection believes it is an
' �I ,t important first step. Its recently issued
'` _ I � �` tfI x-,ts statewide sludge management plan includes
f s .`} a requirement that all new sludge composU
I. 6=�, .3F , � q - ing facilities be enclosed. Existing static pile
I _ ____ _ . .,,._. 1. M" °'>; facilities (the state has no windrow or aer-
• I"' t • ¢ �„.• � aced windrow operations) will he "grand-
_ ii 9 - t.l fathered", although any expansion at those
`t ,3 .,t,. sites must be enclosed. The primary motiva-
i i , � ';?' k r tion for the requirement, says Helen Chase, '
.•i '. ', , Chief of the Residuals Management Pro-
' t «� i r+ 1 . <'t`. 1...c7, .1..1'.(11 gram, is to control odors.The new regulation
- ` , has yet to be tested because the only permit
,.,�,,,''�t 4y - —` applications for composting submitted so far
a ,i --k»k-.„_ v `,� ,�. • �` " have been for an in-vessel facility.
n ` -,c4.. `�F}� . •�=-r_ yK - . OPERATIONAL EXPERIENCE
; ? t. T, ::: ' .., -4'. c.' "" Based on conversations with operators at
fit .�1 k p�.-�'ytl's s" .- a number of static pile composting facilities,
"" ' - - ti",= - there is no set conclusion on whether an aer-
ated static pile facility should be enclosed, or
II. _ __ The active composting area at at least put under cover. The following is a
Maryland's Montgomery County summary of the comments received:
- project was enclosed by heavy fabric Montgomery County,Maryland:This facil-
- sides as part of an odor control
+ "+ program. ity, designed to handle 400 wet tons per day
° of sludge,currently receives 200 wet tons per
+ ka"_ ._ �,•,. day. When it first began operating, the mix-
/ 1 Covers with solar panels ing area and the active composting piles
-di have worked effectively at were in open-sided buildings. The screening
Denver Metro's aerated operation was put in a separate building.The
- windrow plant.
..f facility is bordered by residential areas and
7 an industrial park From the beginning, LL re-
cowed odor complaints
.. 4
John Donovan of Camp Dresser McKee in "We did odor emission and odor modeling
Boston sees a trend toward designing covers work and found that when the atmosphere is
�� -,;,�m,:N�. for aerated static pile facilities. "For the ac- very stable, low level odor emissions from
.. - tive composting piles, we are generally using the aeration pad would accumulate close to
z buildings where the sides can be closed if the ground and travel off site very slowly,"
"�'� j necessary, and air collection and odor control says Charles Murray, chief operator. "There
systems can be added," he says. "With cur- was no dispersion in the air. That pointed to
I ) „- I rat .,;,.(:-.1' fsacs:. ing and storage, we use a shed type of ar- the need for enclosure."
-,,,,,La�„,,,,�- „id, rangement." The active composting area was enclosed
Phe rationale for covers, he adds, is to con- by putting up heavy fabric sides. Dispersion
" • . trot moisture the most critical aspect of enhancement technology was used to ex-
IN composting—and composting—and to insure that weather con- haust the air into the atmosphere (the pro-
ditions don't have a severe impact on the op- cess air goes through a separate odor scrub-
1 • ". 't � .l. eration. "From just purely an operational burg phase) Murray says that a study of
,,4j standpoint, iL is best to keep the front end odor sources at the facility measured by
>r. loader operators dry to enable them to work surface area—found that about 50 percent
most effectively and to keep outside fac- come from the surface area of the compost
tors—such as slippery conditions—from af- piles. About two percent are from the mixing
feeling them." area and 11. percent from the curing piles(be-
The trend toward covering and/or enclos- cause at that point the woodchips are re-
ing these operations has resulted in more ex- moved and the pile area is much smatter).
pensive facilities. "Costs can increase by up More permanent garage door-like sides will
to one-third," says Donovan, "especially if be installed to replace the fabric walls this
- odor control is required." spring. Mechanical mixers are also being in-
When designing a facility or expanding an stalled,and that area will be enclosed as well.
existing one. determining how far to go with I,00king back, Nlurrolsgrkc{{ll!u-��des that if
4. /X2.1
I,
I'lililfllARY 1988 {.5
j
they knew five years ago what they know is about 18' to 20' high so it can accommo-
now about controlling odors,it may not have date dump trucks and front end loaders.
been necessary to enclose the process area. Three blowers have been installed to aerate
"We believe that 95 percent of odor emis- the compost material.
sions at this site come from the process air The active composting area is uncovered,'.
' stream. If we had been able to solve that however the township is considering the in
problem we might have been alright." None- stallation of two buildings within the next
theless, from a political standpoint, Murray year, similar in design to those built by the
says it was best to enclose as much of the Sussex County MUA.The primary reason is
operation as possible because of the location process, not odor, control. "We have found
of the site (especially since a hotel and res- that composting in bad weather makes it dif-
taurant are opening right outside of the facil- ficult to get a good quality product," says
ity's gate!).The cost of the original enclosure Jim Crooks. "We haven't had that many
F odors, and we aren't in an odor-sensitive
' y., area.'
'7's'„e,: Each building could accommodate several
cells of com post.The exhaust system will be
,apa- 4, ,,- comprised of two, four foot diameter high
���—� speed fans.Estimated costs for the buildings ,
//' are between $20,000 and $25,000 each.
"--„,,,_.' - Charlottesville, Virginia: The Moores
x Creek Wastewater Treatment Plant has a 4.5
dry ton per day composting facility.Not long
' after operations began, it was decided to
till,el
cover the entire composting area with a steel
building. "This keeps the operation as dry as
ny, possible," says Norman Wescoat.
4. lik. bt Nashville, Tennessee: The Central Waste-
..,.. - t` ' water Treatment Plant recently expanded its
_ 1 operation from 20 dry tons per day to 40 dry
''`.. tons per day.Structures with open sides were
n v^,- - 4.1... - -,- . e..c,, , , _ built to cover the curing/screening and the
_ pugmill mixing areas. "Our main problem
Five prefabricated steel was $2 million, which included the fabric was that when the compost was wet, it was
buildings were constructed sidewalls and extending the ends of the difficult to screen,"says David Snyder,oper-
to house compost piles at building to accommodate the exhaust sys- ator of the facility. "The covers are needed
New
project reach with ex County tem. The permanent walls being installed for effective year-round operation. To have
independent aeration will cost about $1 million. covered the whole area would have been very
systems. Philadelphia:This sludge composting facil- expensive."
ity has been expanded to accommodate up to Scranton, Pennsylvania: The Scranton
400 dry tons per day of sewage sludge. Cur- Sewer Authority has two curing buildings
rently, the facility is composting 175 dry used to get the material dry prior to screen-
tons per day. As part of the expansion and ing. Covering the active composting piles
upgrade, several new buildings were con- would be economically prohibitive, says AI-
structed.There are two 64,000 sq. ft. drying fred Polidori, manager of the authority, who
sheds,open on all sides,with skylights in the adds that cold weather and rain don't seem
roof.Aeration blowers have been installed to to affect the composting process itself. "Lib-
further dry the compost prior to screening. eral use of wood chips and an insulating blan-
"These sheds will be a big help, particularly ket keep the piles from getting too wet," he
during the rainy seasons when the material says. "And when the weather is really bad
would get so wet that screening capacity we make sure the piles we want to screen two
would decrease," says Kate Ellis, assistant, weeks from now are put under cover and
manager of operations. spread out so they can dry for 10 days to two
The city never considered covering the ac- weeks."
tive composting piles because the area is too
vast. Ellis adds that very few problems are RESOLVING THE DEBATE -
experienced during that phase of compost- While there is no definitive answer on
ing. "We can control the process by adjust- whether or not to cover or enclose non-
ing aeration rates." reactor composting operations, there is no
Mechanical mixers, housed in an enclosed question that if a facility can afford it,covers .
building, just began operating. This should over the curing/storage area—particularly
help to reduce odors at the site. "With front prior to screening—can improve efficiency
end loaders, mixing was the most odorous and ease of operation. Covering the active
part of the operation," says Ellis. The city piles will enhance process control, and en-
has also retained Black and Veatch to do an closing this area can be a beneficial first step
odor control study at the facility to evaluate to controlling odors from the piles. Finally,
optimum methods. from a public acceptance viewpoint, out of
Springettsbury Township, Pennsylvania: sight, out of mind still seems to be the most
Recently, this 4.5 dry ton per day operation palatable route. At that point, budget, and
built an open-sided structure—about 100' X the ultimate fate of the facility, become the
200'—to cover its curing piles. The building determining factors. .y ■
36 BioCrci.e. sra9As1
STABILIZATION RESEARCH
i
TEMPERATUREifP ATHOGEN CONTROL
AND PRODUCT QUALITY
,,
• .
COLOGICAL, energy, and sari- however, the number designed for MSW is
tary requirements have drastically very small,although plants designed to com-
changed the management of ur- An analysis of the post sewage sludge are quite numerous, and
ban, i.e., municipal solid wastes the co-composting of MSW with sewage
(MSW) in recent years. Uncon- effectiveness of sludge is gaining in interest.
trolled landfilling, tipping, and in- The utility of composting is lessened by
cineration were ahnost the only various systems to two potentially important risks or dangers
means of disposal in practice until a few associated with the end use of the product.
years ago. By that time the invasion of reduce the The drawbacks are: 1)possibility of releasing
wastes into the environment had become so heavy metals into the environment- and
extensive and its concentration in some pathogen content 2) the danger to human and animal health
places so great as to bring those methods posed by human and animal pathogens that
into question. of the compost may also be present in the product. This pa-
The recent economic crisis in Europe has per is specifically concerned with the second
led to a change in the concept of waste. It is product. risk, especially with the effectiveness of the
no longer considered as being whatever soci- various compost systems to reduce the path-
ety has to eliminate, and instead,is regarded ogen content of the compost product.
as a source of recoverable energy. The in-
crease in the extent of recycling wastes made Marco de Bertoldi, PATHOGENIC MICROORGANISMS IN MSW AND
more apparent the resulting reduction in Franco Zuccorli, WASTEWATER SLUDGE
amount of waste to be disposed and the cor- Sludge and MSW may contain huge popu-
responding lowering of disposal costs. M Civdi❑t lations of pathogenic microorganisms—
The fraction of MSW presently of greatest bacteria, viruses, fung
i, and parasites. The
interest is the readily biodegradable fraction. variety of the types of microorganisms is in-
The reasons for the interest are two-fold: dicated by the list in Table 1. Some patho-
that other than in the U.S., it is the largest gens, such as parasites and viruses, can not
fraction (60 - 70 percent), and that it poses reproduce outside of a host, and as such may
the greatest danger of pollution. survive for a long time in a waste without
Because of its heterogeneous chemical increasing in number. By using assimilable
composition, the biodegradable organic frac- matter in the waste as substrate,other path-
. Lion is an ideal substrate for an entire series ogens (e.g., bacteria and fungi) may repro-
, of microorganisms, making it possible to use duce and gain in number with the passage of
in several different microbial transformation time.This latter group makes it necessary to
processes. For example, the biodegradable provide conditions during the composting
fraction of MSW can be used in the produc- process such that the microorganisms not
tion of biomass, animal feedstuffs, methane only are reduced in number, but also are un-
(through anaerobic digestion), ethanol able to grow and multiply in the mature com-
(through fermentation), and organic fertil- post.
izers and soil amendments (through com- When the compost product is applied to
posting). the soil, its pathogenic populations are ex-
Low energy costs and the existence of posed to the homeostatic properties of the
good outlets make composting the most soil and to competition with microorganisms
widely used of the five processes. A large indigenous td the soil.The result is a further
number of industrial composting plants reduction in the number of pathogens. De-
ranging in capacity from a few tonnes to 100 spite the reduction, there is the risk that
or more tonnes per day have been con- some of the pathogens may reach man in suf-
structed or are being planned. In the U.S., ficiently high numbers as
to cause disease or
•.' �U�li�Pi';a-unev 1988 43
food poisoning.Hence,it is essential that the
FIGURE 1 number of surviving pathogens in the com-
COMPOST SWDGE ADDED post product be sufficiently low as to impose
REMOVED HERE a minimum or even no risk to health and hy-
HERE giene.
Technically speaking, the necessary reduc-
_ tion could be accomplished through steriliza-
tion of the product. Unfortunately, steriliza-
s a a c; Lrv/zoi //a% � r z lion not only is economically impractical, it
�� �� --- also would not completely eliminate the risk
of the re-growth of some pathogens (e.g. sal-
Fig. 1. Diagram of a turned pile. monellae). In the absence of competition, the
latter could grow beyond measure. Further-
more, complete sterilization would not be
necessary because the soil, which almost in-
• variably is the destination of the compost '
product, already harbors certain pathogens
Ehience shows Table 1. Pathogens likely to be tound In solid (e.g. Clostridium tetani, Aspergillus fumiga-
per urban waste and wastewater sludge. tus). It would be a superfluous undertaking
that total coliforms, and a waste of money to attempt to elimi- .
PATHOGEN DISEASE nate pathogens naturally present in soil.
fecal streptococci Because of this situation, composting
Virus must guarantee that all pathogenic microor-
enterobacteriaceae Enterovirus gastro-enteritis,heart disease, gamsms not indigenous in the soil and pos-
meningitis ing a danger of contamination at sufficiently
certain viruses, and Rotavirus gastro-enteritis high concentrations be reduced to a level
Parovirus gastro-enteritis that eliminates danger. Otherwise, there is a
arasite ova can Adenovirus respiratory tract infections, risk of direct transmission of disease to hu-
p conjunctivitis mans who consume the contaminated food
Hepatitis A virus viral hepatitis crops or of indirect transmission through the
serve as satisfactorily Polio virus poliomyelitis consumption of animals fed on contaminated
Ecovirus meningitis feedstuffs.
reliable indicators. CDxsaDhfYfrns meningitis There are two main problems associated
with the reduction of pathogens: 1) the ex-
Bacteria tent to which the sanitization of the com-
Salmonella(1700 types) typhus,salmonella posting material should proceed; and 2) the
Shigellae sigellosis method or methods of determining the de-
Mycobacterium tuberculosi tuberculosis gree of sanitization completed. The answer
Vibrio cholera° cholera to the first problem is a matter of economics.
Escherichia tali gastroenteritis Waste, by definition, must not be burdened
Yersinia enterocolica gastroenteritis with an "overhead" in the form of cost of
Clostridium perlingens gangrene
Clostridium botulinum botulism transformation into compost that would
Listeria manocytogenes meningo-encephalitis make the end product non-competitive on
the open market. Consequently, extent of
fungi pathogen reduction must be a compromise
Candida sp. systemic and skin mycoses between cost of processing and benefit accru-
ing from a safe, sanitized end product. De-
Tricosporon cutaneum skin mycosis
Aspergillus lumigatus lung mycosis gree of sanitization can be determined either
Tricophyton sp. skin mycosis during or at the completion of the compost-
. Epidemophyton sp. Microspor skin mycosis ing process.
Microsporum sp. skin mycosis Sanitization is accomplished in compost-
ing by the high temperatures characteristi-
Protozoa tally attained and maintained in a compost-
Eutamoeba amebiasis ing mass.Level of temperature and length of
Giardia lamblia giardiasis its duration must be selected on the basis of
Balantidium coli balantidiasis a logarithmic reduction of the principal path- .
Naegleria fowled meningo-cephalitis ogens. The degree of the reduction that
A. canthamoebe meningio-cephalitis should be attained is as yet to be defined.Na-
tions have individually established tempera-
Helminths ture standards ranging from 55°C to 65°C
Ascaris lumbricoides ascariosis covering a time-span ranging from 24 hours
Ancylostoma sp. ancilastomiosis to 3 days.
Necator amaricanus necatoriasis Before being marketed, the compost prod-
Enterobius vermicularis enterobiasis uct should undergo a series of analyses to de-
Sfrongyloides stercoralis sirongilaidiasis termine the degree of its sanitization. Some
Toxocara sp. larvae in the viscera laboratories base this determination on the
Thrichuris thrichuria thricuriasis disappearance of particular groups of patho-
Taenia saginata tapeworm gens, acting on the assumption that other
Hymenolepsis nana tapeworm pathogens simultaneously disappear. Others
Echinococcus gmnulosus echinococcosis Echinococcus mulfilo°ularis rely upon the use of indicator microorgan-
isms. Experience thus far shows that total
tai rifler.
44 RIOt;YC1.F,
coliforms, fecal streptococci, enterobacteria- and fungi, readily soluble substances un-
ceae, certain viruses, and parasite ova can dergo the transformation that constitutes
serve as satisfactorily reliable indicators. composting. The upshot is that the metabo-
For an indicator to furnish reliable infor- lism and growth of the pathogens is impeded
mation, it must satisfy four requisites: by a shortage of assimilable organic matter.
1) It must always be present in suffi- Moisture:The moisture level in waste usu •
-
ciently great numbers in the raw material ally is sufficiently high to support pathogen
to be composted. growth. A very high moisture content, such
2) It must belong to a group that has the as that in sludge, does not impair pathogen
same reactions to the treatment (i.e. ther- development because many pathogenic mi-
me] changes). croorganisms, particularly the bacteria, are
3) As a safety margin, it must have a re- facultative anaerobes. At moisture levels
sistance greater than that of the patho- lower than 25 percent, all microbial growth,
gens to be eliminated. including that of pathogens, slows and even-
4) Tests involved in determining its iden- tually ceases. Consequently, conditions pre-
tity and number must be simple and inex- veiling in cured, stabilized compost would
pensive. not be conducive to a regrowth of patho-
One of the most controversial problems gens—provided that the moisture content re-
Only certain
under discussion is the degree to which indi- mains lower than 30 percent. y
cators must be reduced in order to have a Temperature: All pathogenic microorgan- pathogenic fungi
safe level of sanitization in the compost. isms have a threshold resistance that varies
The aim of this present research was to from one group to another and with environ- and bacteria can
study several different composting methods, mental conditions. Sporogenous and non-
analyzing raw materials and finished prod- sporogenous can survive exposure to tem- multiply In compoSC ucts for the presence of a particularly impor- peratures above 100°C. Consequently, no 1
tant pathogen—Salmonella sp. and two compost process (system) can completely and only under
indicators—total Coliforms and fecal Strep- eliminate such microbial forms. Fortunately,
tococci—which seem the most suitable of all the most dangerous of the pathogens in certain
for this job. wastes, as far as the environment and agri-
GROWTH FACTORS AND PATHOGEN culture are concerned, are neither sporoge- CITCumStanceS.
G OW GROWTH
FACTS nous nor thermophilic. As such, they can be
eliminated through a rather mild heat treat-
Only certain pathogenic fungi and bacteria ment.
can multiply in compost, and only under cer- Obviously, the effectiveness of heat treat-
Lain circumstances. Although viruses and ment is a function of both the temperature
parasites can survive for a long time in the attained and the length of exposure to that
raw material to be composted, they cannot temperature. Moisture has the technical ef-
multiply outside of their respective hosts. feet of increasing the conductivity of the ex-
The subsequent paragraphs and sections dis- posed mass.Sanitization is brought about by
cuss the principal factors that affect the high temperatures (e.g., 65°C) generated in
growth and survival of pathogens in com- the composting mass.The sanitization effect
post. is greater if the moisture content is relatively
Organic Matter: Because all pathogens in high; and in fact, the lethal effect is much
a waste are heterotrophic, their survival is less pronounced if the material is relatively
dependent upon the availability of organic dry.
matter that can be metabolized by them.The It is essential that the lethal temperature
molecular composition of the organic matter be reached simultaneously in all parts of the
in fresh waste—and more so in sludge—is ex- composting mass. Both requirements (all
tremely heterogeneous. Included are sub- parts of the pile and simultaneity)are techni-
stances that range from short-chain organic rally very difficult to achieve.
acids to highly complex molecules such as Oxygen Supply: Temperature rise in the
lignin. This diversity results in a good sub- composting mass represents the accumula-
strate for a wide variety of microorganisms. tion of heat released through exothermic re-
Thus, bacteria and pathogenic fungi gener- actions. Because the reactions are bio-
ally can metabolize readily assimilable or- oxidations, an adequate supply of oxygen is
genic matter such as the simpler alcohols,or- a requisite. Consequently, the attainment of
gaic acids, sugars, etc., whereas they high temperatures is possible only when suf-
cannot multiply on complex compounds such ficient oxygen is available for oxidation. In
as cellulose, lignin, and humic compounds. its absence, anaerobic processes take over
This limitation places the pathogens in an and heat generation is sharply curtailed.The
unfavorable competitive position with re- result is the failure of temperature to rise.
spect to the non-pathogenic microorganisms Microbial Competition and Antagonism:
indigenous to the waste. In the composting Microbial competition and antagonism rank
process, a gamut of non-pathogenic organ- among the most important of the factors in
isms transform the organic matter of raw the control of pathogens in composting. The
waste into simpler compounds through min- number of indigenous(i.e.,"native"or"natu-
*--
eralization and humification. In cured com- ral") saprophytes involved in composting is ' ' y -,'?.e
post, the residual fraction consists mainly of enormous. By contrast, the population of
stable polymers, often combined to make up pathogenic microbes is numerically insignifi-
a complex humic fraction.Through the meta- cant.This combination of a highly dense het-
bolic activities of the indigenous bacteria erotrophic population and very small patho-
FF,a RUARY 1988 45
genic population is characterized by a
relatively high degree of antagonism and in- FIGURE 4 con+rosnNG WI N FoeceD AeennON
tense competition for nutrients in which the
minute pathogenic population is definitely
the loser. The disadvantage is intensified by
the fact that composting material is not the
natural environment for pathogens. - -
PRACTICAL COMPOST SYSTEMS
A principal objective of this paper is the rtF
evaluation of several types of composting *`viz�- E`""":"""
_
systems in terms of their effectiveness in COMPOST
pathogen destruction. The evaluation in- "„o:�JORE
eludes an analysis of raw materials (waste)
and finished product for the incidence of the WRIER TRAP
particularly important pathogen,Salmonella FOR CONDENSATES rot pEEry DECQ
..o°.
sp. and two indicator microorganisms—total
conforms and fecal Streptococci. These two
indicators seem to be the best suited to the
task.
Table 2 presents a brief classification of °
compost systems in use at the time of this __________ �E„"
PEN SYSTEMS r� _.
Turned Pile:
Turning alone does not ensure the attain- a ,a
Ae MEOW
ment of a consistent or satisfactory oxygena-
tion. Within an hour after the application of FLAN VIEW
turning, oxygen levels within a pile drop
drastically, and microbial biooxidative ac-
tivity is correspondingly reduced. Conse- �. �,•
quently,to ensure adequate oxygenation,the " °
pile must be turned frequently.However,pro-
1---H >WA
viding the requisite frequency of turning CROSS SECTION A-A
leads to problems of a technical and eco- ��p"
nomic nature. (See Figure 1) a-e
Among the critical points to keep in mind Fig. 2. Diagram of an aerated static pile (bottom suction).
about the turning operation is the impor-
tance of periodically exposing material from
the outer layer of the pile to the conditions
prevailing in the interior of the pile. Pile size
is another important consideration. Thus, the flow of air leads to the development of
piles higher than about 3 m. are difficult to passageways ("short-circuiting")and sizable
aerate to the extent needed for satisfactory sections are not aerated. Because uniformity
sanitization. and freedom of air-flow are functions of the
Five experiments were conducted involv- porosity of a pile, the addition of materials
ing the turned pile approach. The raw mate- such as wood chips helps to raise the permis-
dal was the organic fraction of MSW ob- sible pile height.
twined from the Deno plant at Pistoia(Italy). The entire pile must be blanketed with an
This organic MSW was mixed with aero- insulating layer (usually of cured, sanitized
• bically stabilized sewage sludge. The piles compost).This ensures that temperatures le-
were 1.5 m. in height, sheltered by roofing, thal to pathogens will be reached in all layers
and turned twice each week. of pile—from the innermost to the outer-
In two of the five experiments, Salmonella most.
persisted longer than 30 days. A consistent Research has shown that such systems
drop in number of fecal conforms and fecal perform fairly satisfactorily if properly oper-
Streptococci was not observed in any of the ated (i.e., air flow not so great as to cool the
experiments. Repeated turning of the mass pile or to dry the material too soon). In our
disturbed the composting process and al- research,we worked with piles,each of which
tered the temperature profile. Nevertheless, had 20 tonnes of material, and was 1.5 m.
oxygen needs in the center of the pile were high and 2.5 m. wide. In two trials, the raw
such as to require turning at least twice per material consisted entirely of the organic
week. fraction of MSW; in another two trials, the
Static Pile: raw material was a mixture of the organic Q�
Bottom Suction: This is a static pile in fraction of MSW and aerobically stabilized'Jr
which air is drawn through the pile by the wastewater sludge.
imposition of negative pressure(bottom suc- "Bottom Blowing": Forced aeration by
tion).(See Figure 2)With such piles,height is blowing air through the pile(exertion of posi-
a critical factor. When they are greater than tive pressure)is a second form of aeration for
2.5 to 3 m.,uniform aeration becomes almost static piles. Such a method of aeration tends
impossible. In a pile that is excessively high, to cool and dry the bottom layers of the pile,
46 BloCYc1.E
leaving the outer layers warm and moist. mesophyllic conditions is ideal for the prolif-
However, with careful operation, a well- eration of Enterobacteria and Streptococci.
sanitized compost can be produced. Inadequate ventilation—regardless of di-
Alternate Ventilation.- As the name sug- rection of air-flow(top to bottom, or bottom
gests,with such a system,bottom blowing is to top)—and consequent failure to reach le-
alternated with bottom suction.The periodic thal temperatures in the upper levels are the
reversal of direction of air flow leads to an most serious disadvantages in the use of the
evenness of temperature level and moisture continuous vertical reactor in which the com-
content throughout the pile. The result is a posting mass is 7 to 10 m.high.This assess-
greater uniformity of sanitization. ment was confirmed by our analyses of mate-
In our experiments, an arrangement was rial obtained from a 100-m' vertical reactor
used that involved two temperature probes charged with a mixture of sludge and organic
and a solenoid valve adjusted to automati- MSW. (See Figure 3)
cally reverse the direction of the airflow as Horizontal Reactors:
soon as the difference between the tempera- As would be surmised from the name of
ture at a probe positioned 20 cm above the the reactor, the composting material is ar-
bottom of the pile and that at a second probe ranged along the length of the unit. The
positioned 1.20 meters above the bottom ex- depth of the mass does not exceed 2 to 3 m.
ceeded 15°C. Findings showed that of the The orientation and depth of the composting
three approaches,best results were obtained mass is comparable to that with the static At moisture levels
with the alternate ventilation system. pile method.The advantage of the horizontal
reactor is the ability to control the course of lower than 25
CLOSED(IN-VESSEL)SYSTEMS the compost process.Because oxygen is sup-
Continuous Vertical Reactors: plied either by turning or by aeration—or percent, all
Several types of vertical reactors have a both—the composting mass can be uni-
com-mon characteristic of processing large formly oxygenated and the temperature can microbial growth,
quantities of material (as much as 2,000 m') be readily controlled, and a satisfactorily
in reactors that may be as high as 9 m.Mate- sanitized product can be produced in quan- including that of
rial usually is loaded into the reactor through City
its top and eventually is discharged from its
bottom Oxygenation is provided by forcing CONCLUSIONS pathogens, slows
air up from the bottom or through perfora- Pathogenic Bacteria and Indicators: and eventually
tions in the bottom floor and through the A major challenge with the marketing and
composting mass. Conditions in these reac- use of compost is the possibility of patho- ceases.
tors are such that bottom ventilation is not genic microorganisms being present in the
sufficient to achieve the desired effects. product. Indiscriminate use of non-sanitized
The attainment of optimum oxygenation compost products could result in the disper-
levels requires a particular rate of air flow. sion of pathogens in the environment, and -
As a result, the mass must be no deeper thereby give rise to a serious threat to the
(thicker) than 2 to 3 m. Because the flow of health and well-being of man and animal.
air in a vertical reactor is from bottom to top, Therefore, all such products must be treated
the terms "depth of material," "thickness of before being released for utilization. The
material," and "height of material" become treatment should be such that the incidence
synonymous when applied to such reactors. of all pathogens in the products be reduced
Deeper(thicker)masses require a proportion- to a level lower than the risk level. The at-
ally greater quantity of air per unit of surface tainment of such a goal on a practical scale
area according to the height of the contained must be preceded by the resolution of two
mass. Supplying this air leads to the devel- problems: 1) Determination of the threshold
opment of hyperventilation in the lower por- level below which pathogens no longer con-
tion of the reactor,where the need for oxygen stitute a hazard;and 2)development of a pro-
is least. The hyperventilation has many gram of monitoring the compost product
drawbacks, not the least of which are exces- with respect to sanitization.
sive cooling and drying. On the other hand, Finding an answer to the determination of
in the upper portion of the reactor,where the a threshold level is not an easy task since the
raw material is introduced and consequently level varies from one organism to another.
the need for oxygen is greatest,oxygenation Moreover, the determination is constrained
is inadequate.The problem is aggravated by by the practical fact that "there is no such
the fact that as the forced air rises through thing as an economically feasible,completely
the mass,its composition changes because of hazardless level." With respect to monitor-
microbial action taking place in the reactor. ing, it must be admitted that the decision as
Thus, CO,concentration gradually increases to which pathogen to monitor is open to
and O, concentration decreases. Conse- question at present. This research attempts
quently,the concentration of O,in the air, by to make a contribution in that direction.
the time it reaches the upper levels of the In view of the wide array of pathogens � �composting mass, is too low to support aero- that could be present in the raw waste, a C0
'�
bic microbial metabolism. The usual cone- thorough analysis of the entire compost out-
quences then occur: development of anaero- put for its pathogen content would become ' '
biosis and failure of the temperature to reach an enormous economic problem.Therefore,it
levels lethal to microbes, and the production would be more practical to select a few repre-
of an inadequately sanitized end product. sentative pathogens that are easy to identify
The occurrence of partially anaerobic and (Continued on p. 50)
FEBRUARY 1988 47
(Continued from p. 47)
and quantify and are likely to be present in
most raw materials(wastes). The genus,Sal- Table 2. Practical Waste Compost Systems
monella, would meet these specifications.
The presence of Salmonella in a product Open Systems
would indicate poor sanitization.
To avoid the necessity of analyzing for all Turned Pile i
types of pathogens,recourse could be had to Static Pile: -suction
the use of indicator microorganisms. Our -air blowing
results,as well as those obtained by others in -alternating air flow
research on the use of fecal coliforms and fe- -blowing with temperature control
cal streptococci as indicators, especially of Closed Systems
the presence of Salmonella, indicate that the
two indicators are abundant in raw wastes Vertical Reactors -continuous
(although Salmonella may not be found at discontinuous
times). The fecal coli and fecal streptococci Horizontal Reactors-static
-movement of material
survive without difficulty under aerobic and
anaerobic conditions.However,conforms are
more sensitive to temperature (as is Salmo-
nella), whereas streptococci are more resis-
tant (45-48°C). In all composting trials, we to control the process. Furthermore, since
found that Salmonella disappeared before rise in temperature is the direct result of the
the conform level dropped to 5 X 102, and biooxidation activity of the microbial popu-
streptococci dropped to 3 X 10'.Both indica- lations, conditions promoting the bio-oxi-
tors can multiply in waste under favorable dation should be provided.
i conditions. Hence,both can be used for indi- iiiiim The conclusion to be drawn from the pre-
; eating regrowth. FIGURE 3 ceding two paragraphs is that from a practi-
At this stage of analysis,it would be inter- cal standpoint, satisfactory sanitization is a
esting to extend the research to include a de- function not only of the method or system
termination of the limits to be established for used in composting the waste,but also of the
the two indicators, and to investigate then i///i/, / /I/ __ conditions prevailing during the composting.
potential as indicators of the presence of '/ Thus, merely turning the waste periodically
pathogenic viruses and parasites. Our stud- ", ' �/�/�� without supplying ventilation does not guar-
tes found that if the temperature of the com- // ///�'�% j antce good sanitization—unless the piles are
jposting mass reaches 65°C and remains at j� /� /���� c low (1-1.3 m.). Conditions in the usual con-
that level for two days,Salmonellas disc - 9/ tinuous vertical reactor(9 m. column of con-
! pears completely.Moreover,under those con- r/ / iJ % tents)are not conducive to the production of
I ditions, the concentration of conform indica- ; /,,,/,,, a sanitized product. On the other hand, suc-
tors is always less than 5 X 10'- and that of / // cessful results were the rule when ventilated
a Streptococcus, less than 3 X 10'. Therefore, d1////// piles and horizontal reactors were used in
those two concentrations could be used ct in-
dicators 9/ /// this research.
I� dicators of the attainment of satisfactory /�/� - --- The most important parameters with re-
sanitization—at least with respect to patho- .�,. �/. A spect to attaining sanitization are the follow-
genic bacteria. ing: 1) The entire mass must be maintained
Compost Processing and Sanitization: Fig. 3. Diagram of at a minimum of 65`C for two to three con-
Composting and sanitization are not neces- continuous vertical secutive days;2)the material must be biolog-
sarily synonymous. For sanitization to take reactor with bottom ically stable so as to prevent pathogen re-
place, certain conditions must be supplied aeration (blowing); growth. Consequently, to be able to decide
during the composting process. In theory, 4 hyperventilated zone; with a reasonable degree of certainty that a
,co
B ne;
the end product can justifiably be considered zone with insufficient rrectly ventilated zo given compost product is hygienically safe,it
i sanitized if the compost process has been oxygen for the correct is necessary to know the precise conditions
properly conducted and the entire mass has processing of the mass. that prevailed throughout the composting
been exposed to lethal temperatures. In prac- process whence it came. ■
tice, meeting those two requirements is not
enough to guarantee the necessary "stabil- Editor's Note:Results of a study on the patho-
ity"with regard to sanitization,inasmuch as gen content of sample composts from facilities
pathogens may "regrow." Consequently, around the U.S., conducted by the Los Angeles
composting must not only drastically reduce County Sanitation District, will be presented in
the number of pathogens, it must also trans- an upcoming issue of BioCycle.
form the waste such that regrowth can not
occur. This can be done by adequately stabi- Marco de Bertoldi is Professor in Industrial Mi-
lizing the organic matter, mineralizing all crobiology, Faculty of Agriculture, University
simple compounds readily assimilable by of Udine,Italy. Franco Zucconi is a professor in
pathogens, and by humifying other com- the Faculty of Agriculture, University of Na-
I pounds. Moreover, the moisture content of pies.Prof. M. Civilini is in the Faculty of Agri-
1 the product should be fairly low (25-30 per- culture, University of Udine. This paper was
cent). supported by a contract with the Commission
Although many factors are involved in the of European Communities,Directorate-General
elimination of pathogens, temperature is the Science, Research and Development Pro-
I only one that can be quantitatively mea- gramme on Recycling of Urban and Industrial
f I sured and controlled.Thus,it should be used Waste. C', , d"1 -'r7 50 BIOCYCLE
ar
PROBLEM PREVENTION
i
PUBLIC HEALTH ISSUES
AND COMPOSTING
HE OBJECTIVE of this paper is zenbur en 1977 found the fun in
P P g ( ) fungus base-
to discuss the public health issues ments, bedding, and house dust.
What are the that are related to the design and Aspergillus fumigatus is common in com-
operations of composting facili- posting operations.Table 1 shows concentra-
potential problems? ties. We place particular emphasis trons of Aspergillus fumigatus found at a
on methods that reduce the im- compost site. Millner et al. 1977 reported
How can the proper pact of potential health problems. similar data. It is heat tolerant and grows
p t' The following are representative incidences well at thermophilic temperatures (above
design and operation which have occurred in the past two years 45°C)and therefore survives the composting
regarding the above issues. process. Passman (1980) and Millner et al.,
of composting 1. At a public hearing in conjunction with a (1977) showed that viable conidia can be re-
p g leaf and yard waste composting site, a covered in the immediate vicinity of agita-
facilities abate their question was asked as to the potential tion of aerosolization of fungal-containing
threat of Aspergillus fumigatus to the material but the counts drop rapidly only a
Im act? health of residents near the site. short distance from the source or a short
p 2. Similarly,the issue of Aspergillus fumiga- time after cessation of the activity.
tus was brought up at a meeting regard- Studies by Clark et al. (1984) showed no
ing a solid waste facility and worker trend to infection or allergic responses to
Eliot Epstein and health. workers at compost sites in the United
Jonathan L Epstein 3. Endotoxins were a concern at a waste- States. The authors found no consistent dif-
water treatment plant having a compost- ference between compost workers and work-
ing operation. Workers were concerned ers not involved in compost activities as de-
about dust and endotmdns. termined by antibody methods. The lack of
4. A soil blender was concerned about the increased antibodies to Aspergillus supports
health of employees in relation to use of the conclusion that, though Aspergillus
sludge compost products. colonization is more common in compost
ASPERGILLUS FUMIGATUS
Aspergillus fumigatus is a fungus which is
ubiquitous. It is found throughout the world Table 1. Levels of Aspergillus lumigatus at a
and is common in a variety of materials,such Compost Site and Surrounding Areas •
as hay,grain, decaying vegetation, compost,
and soil. Aspergillus fumigatus is found in Location Concentration
commercial soil potting products (Millner et CFU/M'
al., 1977) and woodchip piles in the forest .
product industry (Passman 1980). Hirsch Mix area 110-120
and Sosman(1976) studied the occurrence of Near tear down pile 8-24
Aspergillus fumigatus in homes.They found Compost pile 12-15
the fungus in 42 percent of bedrooms, 56 per- Front end loader operations 11-79
cent of bathrooms, and 85 percent of base- Peritery of compost site 2
As-
ments. It was the fourth most common mold Centrifuge operating room CO 4,-11
38-75
in households and present in all seasons. As- Grit building ,-1 0.2c1;'> 2
Pump house . .-x,r't 10
pergillus fumigatus was more frequent in Background level 2
homes with pets. Similar data were found by
Solomon(1974), who investigated the indoor Data from compost site at Windsor, Ontario, Canada. Clayton
atmosphere of 150 homes. Salvin and Win- Environmental Consultants Ltd Windsor, Ontario. 1983.
50 itioCycia. AUGUST 1989
workers, infection with the organisms is not.
One would expect a rise in antibodies to the
fungus if there were infections due to the fun- The data today show that many other work
s
Severe Aspergillus infections from any of environments have higher levels of endotoxins and
the species occur almost exclusively in peo-
ple who are severely debilitated or immuno-
compromised (Rippon, 1974) e.g. persons workers are at greater risk than at composting
with kidney transplants, leukemia, or lym- faC111t1eS.
phoma.
ENDOTOXINS dotoxins and workers are at a greater risk
Endotoxins are noxious substances pro- than at composting facilities.
duced by gram negative bacteria. The term Dr. John Rippon, Director of The Mycol-
endotoxin refers to the gram negative cell ogy Services Laboratory, The University of
wall lipopolysaccharide. It is produced by Chicago, Division of the Biological Sciences
many bacteria including many which are and The Pritzker School of Medicine (per-
non-pathogenic. This suggests that it plays sonal communication) states that:
no part in virulence,i.e. in the degree of dis- "It is concluded therefore that the ex-
ease producing properties of a species of bac- amination and monitoring of compost
teria. One of the more important properties operations in several sites in several
of these lipopolysaccharide substances is counties has not indicated a significant
their heat stability. The metabolic products level of bio-hazard risk associated with
of gram negative bacteria may remain in the viable bacteria dr fungi, dust or endo-
dead bacteria or their fragments after they toxin. Studies directed at detecting
break up. Endotoxins can be present in air- work-associated health problems have
borne dust particles.If inhaled in large quan- also been unable to find significant or
tities they can cause tissue damage. Air- consistent abnormalities. It would ap-
borne endotoxins have been directly or pear that at the present time, signifi-
indirectly implicated in occupational worker cant bio-hazards from composting op-
health problems in many different situa- erations have not been established. It
Lions. Some examples are: agricultural ani- should be noted that this environment
mal housing and animal processing plants of composting operations does contain
(Jones et al., 1984, Olenchock, et al., 1982), potential bio-hazards (fungal conidia,
textile mills and cotton dust (Olenchock et endotoxins, allergins, etc.) and particu-
aL, 1983,Castel en et al., 1984),poultry han- lar individuals hypersensitive to aller-
tiling plants(Thelin et al., 1984),cotton card- gens or predisposed to opportunistic fin-
ing (Rylander et al., 1985) humidifiers (Ry- fections may be at risk." ii
lander and Haglund, 1984) wastewater ),
treatment plants and composting operations PATHOGENS
(Rylander et al., 1982; Rylander and Lund- The main pathogen groups found in sludge
holm, 1979; Rylander et al., 1977). are:
Levels in composting plants showed air- • Bacteria.salmonella,tuberculli bacteria,
borne endotoxin ranging from 0-001 to 0.014 yersinia
mg/m'. In an office environment, levels as • Virus: entroviruses (poliovirus), hepati-
high as 0.39 mg/rre were found(Rylander and tis, adenoviruses
Hagland, 1984). • Helminths: nematodes (roundworms),
Human exposure to large quantities of air- cestodes (tapeworms)
borne endotoxin produce symptoms which • Protozoa: giardia lamblia, entomoeba
include fever, diarrhea, fatigue, headaches, histolytica i
nausea, irritation, nasal irritation, chest These pathogens are sensitive to heat and
tightness, cough, and expectoration of are eliminated at temperatures exceeding
phlegm(Olenchock et al., 1982). 55°C (131°F). This is the basis for the Fed-
Many of the normal bacterial flora of hu- eral Regulations 40 CFR Part 257 "Criteria
mans are gram negative. The mucous mem- for the Classification of Solid Waste."Proper ' i j
branes of the nose, throat, and gut contain composting should result in the elimination
large numbers of gram negative bacteria, of these organisms. Recently,a document by
both living and dead and large amounts of William Yank°of the County Sanitation Dis-
endotoxins (Sheagren 1986). There is no evi- tricts of Los Angeles County was produced
dence that the physical presence of large for the U.S. EPA providing results on patho-
numbers of gram negative bacteria,living or gen analysis of sludge products from various
dead, or extremely large quantities of endo- facilities (Goldstein et al., 1988).
toxins within the gut (intestines of man) An intensive sampling was conducted at
cause any symptoms of any kind. one static pile facility in Pennsylvania and a
Table 2 shows endotoxin levels in compost windrow facility in California. Subsequent
from several sources.The endotoxin levels in bi-monthly samples were carried out at 24
sludge compost, 3.9 to 6.3 ng/gm were Simi- sites which included static pile,in-vessel,aer-
lar to levels found in compost from leaves, ated windrow, heat drying, and other sludge to
cattle, and sheep. facilities. °a'� , ,F
i.
The data today show that many other The bi-monthly samples at 24 sites gener-
work environments have higher levels of en- ally showed low bacterial contamination in
aI ! .
BI0CYCLE AUGUST 1989 51 Y,.II
4i'.
I
i
•
' recycling of wastes,it is concerned about the
public health issues discussed. Not only are
One of the most significant aspects in the wens concerned about the siting of the fa-
One cilities,but they are also concerned about the
maintenance of good environmental and health design and operation as related to health and
I environmental •issues.
conditions at a composting site is the provision of KEY FACTORS IN DESIGN AND OPERATION
sound operator training. The key factors in the design and opera-
tion of composting facilities as related to
health of workers and the surrounding popu-
lation are:
compost • Uniform mixing
p products. Some salmonella were • Moisture control
found in air-dried sludge,thermal filter press • Temperataure control
sludge, and one static pile, and one in-vessel • Dust control
facility. The study found that sludge prod- • Hygiene conditions
ucts were free of pathogenic viruses and via- —building ventilation
ble parasite ova.Sahnonella was detected in —vehicle/equipment ventilation
a significant number of samples, and a non- • Odor control
pathogenic variety of Yersinia was also • Paved surfaces for leachate and runoff
found at very high concentrations. The au- control
thors indicated that there were no known Uniform mixing is essential for good com-
cases of sahnonellosis traceable to the use of posting and adequate disenfection since
sludge-based soil amendments- Unfortu- clumps of materials may not be exposed to
nattily,the study did not describe the facility high temperatures for pathogen destruction.
design and operations. A re-examination of Furthermore these clumps could remain an-
data clearly shows that at facilities where aerobic and produce odors.
temperaturesexceeding 55°C were main- Moisture, temperature,and aeration affect
tained throughout the pile and cross contam- the composting process; their control is es-
ination between sludge and compost did not sential for disinfection and pathogen de-
occur,the compost was pathogen free.We 10- struction. These factors also impact odor
sated most of these facilities and upon re- generation.Low moisture(less than 25%)re-
view determined that the design and opera- duces biological activity and slows the com-
tions contributed significantly to the posting process. At low moisture contents
potential for pathogen survival in compost more dust is generated which can impair
products. The main contribution of this worker health. At high moisture contents
study is to point out that pathogen survival (greater than 60%)porosity of the mix is re-
can exist in compost products, as well as in duced, and the potential for anaerobic condi
sludge which may be land applied. tions exists which results in excessive odors
and reduces the pile temperature. Tempera-
ture control is essential for pathogen de-
struction and effective composting. For
. pathogen destruction, temperatures exceed-
ing 55°C need to be maintained for several
Table 2 Comparison of ErMofoxin Levels in days. Temperatures in the 45°C to 55°C
range enhance biodegradation and reduce
Composts from Various Sources
the potential of odors.Proper aeration is nec-
essary to maintain aerobic conditions and
Source Levels control temperature and moisture.
Dust is principally generated by vehicular
Sludge compost 3.9-6.3 traffic and during screening operations.
Cattle manure 2.3 Good housekeeping such as sweeping and
Sheep manure 4.9 watering roads can control much of the dust
Leaf compost 4.5 g
generated by vehicles. Proper moisture
maintenance during composting and selec-
tion and design of screening equipment and
housing will result in low dust emissions. In
municipal solid waste composting operations
Data from Windsor, Ontario, where the which involve shredding, grinding and sepa-
Provincial Government's public health au- ration, adequate ventilation in the facility is
thorities have conducted monthly analysis of necessary.
compost from 1980 to 1985, showed no sal- Hygienic conditions in buildings and vehi-
monella or other pathogens. Similarly, at cles are important to worker health. These
Nashville, Tennessee, for the past year no principally relate to dust control-The princi-
salmonella were detected.In both of these fa- pal mitigation measures involve ventilation
cilities the compost product has also been and air filtration. Air conditioning and/or
free of at ens.p ho
g dust filters in front-end loaders and other ve-
The u p bhc today is very much concerned hi sled should be installed and proCrl� on-
with health issues and, although it is favor- twined. 1 :,� d, 'l,},� -
ably disposed to composting as a method of The single most vex&tg pfdbireirC4 com-
52 BI0CYCLE
AUGUST 1989
posting operations has been odors. Odors One of the most significant aspects in the
have plagued composting facilities regard- maintenance of good environmental and a
less of type, i.e. static pile, windrow or pro- health conditions at a composting site is the
prietary in-vessel. Odor control can be provision of sound operator training. Cou-
achieved through proper aeration and other pled with the training is the need for good
operations, odor scrubbing and good house- operation and maintenance manuals. These
keeping. Haug (1980) points out that odor manuals need to be clear,concise and specific
emissions can increase significantly if the to the facility.All too often one finds generic
thermodynamic and operational constraints manuals loaded with vendor equipment spec-
are exceeded. In most cases the surface odor ifications which neither instruct the operator
emission rate is greatest at the beginning of as to the importance of various operations,
the compost cycle and decreases with time. nor instruct the operator on the mitigating
Leachate and runoff contamination of measures that must be taken to correct or
ground and surface waters have not been a avoid problems. ■
problem at composting sites since most ac-
tivities are on a sealed paved surface or un- Eliot Epstein is Chief Environmental Scientist
der a roof. Provision needs to be made for with E&A Environmental Consultants in
collection and disposal of any excess water Stoughton, MA. Jonathan Epstein, M.D., is
which is a by-product of the composting op- Assistant Professor of Pathology at the Johns
eration. Hopkins Medical Center in Baltimore.
'h
LITERATURE CITED
1. Epstein, E., Willson, G.B., Burge, W.D., Mul- Occupational exposure to airborne endotoxins
len, D.C. and N.K. Enkiri. A forced aeration sys- during poultry processing. J. 7bxicol Environ
tem for composting wastewater sludge.J. Water Health 9:339-349, 1982.
Pollut Control Fed,48:688-694, 1976. 14. Olenchock,S.A., Castellani P.M., Cocke, J.B.,
2. Lundholm, M. and R. Rylander. Occupational Beloit, D.J., Hankinson,J.L.,and J.C.Mull. En-
symptoms among compost workers.J.Occn Med dotoxins and acute pulmonary function changes
22:256-257, 1980. during cotton dust exposures.Proceedings Cotton
3. Epstein, E.and J.E. Alpert. Pathogenic health Dust Research Conference. 1983.
aspects of composting sewage sludge. A report 15. Castellani R.M.,Olenchock, S.A., Hankinson,
submitted to the State of Utah Department of J.L., Millner, ED., Cocke, J.B., Bragg, C.K.,
Public Health and Central Valley Sewage author- Perkins, H.H., and R.R. Jacobs. Acute broncho-
ity, Salt Lake City. 1980. constriction induced by cotton dust: Dose-related
4. Burge, W.D., and P.D. Millner. Health aspects responses to endotoxin and other dust factors.
of composting.primary and secondary pathogens. Ann. Int. Med. 101:157-163, 1984. j
In "Sludge- Health Risks of Land Application." 16. Thelin, A., O. Ziegler and R. Rylander. Lung
C. Bitton, et al. (Eds.) Ann Arbor Sci. Pub. Inc. reactions during poultry handling related to dust
Ann Arbor, MI. 1980. and bacterial endotoxins. Eur. J. Resp. Dis.
5. Clark, C.S. Bjornson, H.S., Schwartz-Fulton, 65:266-271, 1984.
J., Holland, J.W., and P.S. Gartside. Biological 17. Rylander, R., P Hagland and M. Lundholm.
health risks associated with the composting of Endotoxin in cotton dust and respiratory function
wastewater treatment plant sludge. J Water decrement among cotton workers in an experimen-
Pollut Control Fed 56:1269-1276, 1984. tal card room. Am. Rev. Resp. Dis. 131:209-213, -
6. Milkier, P.D., Marsh, P.B., Snowden, R.B., and 1985.
J.F. Parr. Occurrence of Aspergillus fumigates 18. Rylander, R. and P. Haglund Airborne endo-
during composting of sewage sludge. Appl and toxins and humidifier diceace5. Clinical Allergy
Environmental Microbiol 34:765-772, 1977. 14:109-112, 1984.
7. Passman, EJ. Monitoring of Aspergillus fumi- 19. Rylander,R.,and M.Lundhol n. Responses to
Batas associated with municipal sewage sludge wastewater exposure with reference to endotox-
composting operations in the state of Maine.Final ins. In: Pahren, H, and Jakubowski, W. eds.
Rept.to Portland Water District. 1980. Wastewater aerosols and disease.Proc.of a Symp.
8. Hirsch, S.R. and J.A. Sosman. A one-year sur- held Sept. 19-21, 1979.Cron,OH. EPA Doc. EPA-
vey of mold growth inside twelve homes. Annals 600/9/80-028 pp.90-98, 1980.
of Allergy. 36:30, 1976. 20. Rylander, R., Anderson, K., Berlin, L.,
9. Solomon.,W.R.Assessing fungus prevalence in Bergland, G., Bergstrom, R., Hanson, L., Lund-
domestic interiors. J. of Allergy and Clinical Im- holm, M., and I. Mattsby. Studies on humans ex-
munology. 53:71, 1974. posed to airborne sewage sludge. Schweiz. Med.
10. Slavin, R.G. and P. Winzenburger Epidemio- Wschn 107:182-184, 1977.
logical aspects of allergic aspergillosis. Annals.of 21. Sheagren, J.N. Role of inhaled endotoxin
Allergy. 38:215-218, 1977. symptoms suffered by workers in the West Wind-
11. Rippon, J.W, Medical Mycology. The patho- sor polution control plant.Paper submitted to the
genic fungi and the pathogenic Actinomycetes. City of Windsor. 1986. P 2nd ed. W.B. Saunders, Chpts. 23 and 28. 1982. 22. Goldstein, N., W.A. Venice, J.M. Walker, and
12. Jones, W., Morring, K.,Olenchock, S.A., WG- W. Jakubowski. Determining pathogen levels in .
Gams, T., and J. Hickey. Environmental study of sludge products.BioCycle 29:44-67, 1988. .`�i '�¢ -
poultry confinement buildings. Amer. Ind Hyg. 23. Haug, R.T. Compost engineering principles -
Assoc.J. 45:760-766, 1984. and practice.Ann Arbor Science.Ann Arbor,MI.
13. Olenchock,S.A.,Lenhart,S.W.,and J.C.Mull. 1980.
6 IOCvCLE AUGUST 1989 53
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