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Home My WebLink About961188.tiff RESOLUTION RE: ACTION OF BOARD OF COUNTY COMMISSIONERS OF WELD COUNTY, COLORADO, CONCERNING SITE APPLICATION OF TOWN OF WINDSOR, COLORADO, AND AUTHORIZE CHAIR TO SIGN WHEREAS, the Board of County Commissioners of Weld County, Colorado, pursuant to Colorado statute and the Weld County Home Rule Charter, is vested with the authority of administering the affairs of Weld County, Colorado, and WHEREAS, the Board has received a site application from the Town of Windsor, Colorado, 301 Walnut Street, Windsor, Colorado 80550, concerning the expansion to an existing wastewater treatment facility located on the following described parcel of land, to-wit: SE1/4 SE1/4 of Section 34, Township 6 North, Range 67 West of the 6th P.M., Weld County, Colorado WHEREAS, the regulations for site applications for the expansion to an existing wastewater treatment facility require review of the site application by the Board of County Commissioners, and further, that various local and state agencies be given the opportunity to review and comment on said revised site application, and WHEREAS, the site application from the Town of Windsor, Colorado, was submitted to the Board of County Commissioners of Weld County for review and comment, a copy of said application being attached hereto and incorporated herein by reference, and WHEREAS, after study and review, the Board finds that said site application is compatible with the Weld County Comprehensive Plan, and that it is in the best interest of Weld County to recommend approval of said application. NOW, THEREFORE, BE IT RESOLVED by the Board of County Commissioners of Weld County, Colorado, that the site application submitted by the Town of Windsor, Colorado, be, and hereby is, recommended favorably to the Colorado Department of Health, Water Quality Control Commission, as being compatible with the Weld County Comprehensive Plan. BE IT FURTHER RESOLVED by the Board that the Chair be, and hereby is, authorized to sign said site application. 961188 ee f)t) hie fi',er PL0079 SITE APPLICATION - TOWN OF WINDSOR, COLORADO PAGE 2 The above and foregoing Resolution was, on motion duly made and seconded, adopted by the following vote on the 10th day of July, A.D., 1996. BOARD OF COUNTY COMMISSIONERS G' WEJ.A COUNTY, COLORAPC) ` a4A, Barbar J. Kirkmeyer, hair u Weld Countylerto the Board z • �rgeeBaxter, Pr -Te Clerk to the Board t , Dale,K. Hall APPR D AS TO M: LnceL. H&b/C� 1) )2/M___I W. / / det r 961188 PL0079 SITE APPLICATION for TOWN OF WINDSOR, COLORADO Rothberg, Tamburini & Winsor, Inc Professional Engineers and Consultants 1600 Stout Street, Suite 1800 Denver, Colorado 80202-3126 © 1996 RTW Project No. RO-2891-SC May, 1996 961188 Contents SECTION ONE Introduction 1-1 Background 1-1 Purpose 1-2 SECTION TWO Wastewater Service Area, Flows, and Characteristics 2-1 Service Areas 2-2 Current Population and Wastewater Flows 2-2 Population and Flow Projections 2-3 Wastewater Characteristics 2-4 SECTION THREE Review of 208 Plans 3-1 SECTION FOUR Treatment Facility 4-1 Existing Facilities 4-1 Wastewater Treatment Process 4-1 Solids Handling Process 4-3 Existing Facility Performance 4-3 Capacity at Recertification 4-4 Effluent Discharge Limits 4-4 1 1 Windsor WWTP Site Application 961188 SECTION FIVE Flood Plain and Natural Hazards 5-1 APPENDICES Appendix A Application for Site Approval Form SEPARATE DOCUMENTS Reassessment of Treatment Capacity Study by RTW I I I Windsor WWTP Site Application 961188 Figures' SECTION ONE Figure 1-1 Regional Map 1-1 Figure 1-2 Vicinity Map 1-1 SECTION TWO Figure 2-1 Service Area 2-1 Figure 2-2 Five Mile Radius Map 2-1 Figure 2-3 One Mile Radius Map 2-1 SECTION FOUR Figure 4-1 Plant Schematic 4-1 Figure 4-2 Site Plan 4-1 SECTION FIVE Figure 5-1 Flood Plain at Windsor WWTP per FEMA 1991 5-1 Figure 5-2 Flood Plain at Windsor WWTP after 1996 5-1 All page numbers indicate the page directly preceding each figure. Windsor WWTP Site Application iii 961188 Tables SECTION TWO Table 2-1 Population, Flow, and Flow Per Capita Data 2-2 Table 2-2 1995 Flow Data 2-2 Table 2-3 Projected Population and Flows 2-3 Table 2-4 Influent Wastewater Characteristics 2-4 Table 2-5 Maximum Influent Loadings 2-4 SECTION FOUR Table 4-1 Windsor WWTP Existing and CDPHE Projected Effluent Limits 4-5 l f I Windsor WWTP Site Application iv 961188 SECTION 1 Introduction The Windsor wastewater treatment plant (WWTP) is operated by the Town of Windsor and treats domestic waste from the Town and the Kodak plant. An additional wastewater source is the Metal Container Corporation facility which discharges into the Town of Windsor's wastewater collection system. The plant is currently permitted to treat 1.5 MGD of wastewater. The proposed recertification would increase treatment capacity to 2.8 MGD. It is anticipated that the expansion and upgrades performed in 1995 will allow the treatment plant to operate at the 2.8 MGD capacity without significant modifications. Background In March 1994, the Colorado Department of Public Health and Environment (CDPHE) approved a Site Application to convert the Windsor WWTP from an aerated lagoon system to an activated sludge type mechanical plant with a design capacity of 1.5 MGD. Plant expansion was necessary to meet discharge requirements established by the Colorado Department of Public Health and Environment (CDPHE) and to provide the needed capacity for the continued growth of the Town. Construction for the plant expansion began in February 1995. Plant startup was in October 1995. The existing Windsor WWTP uses an earthen basin extended aeration activated sludge process with a "Biolac" fine bubble aeration system. Also included are preliminary treatment (grit removal and in-channel grinder), ultra-violet disinfection, and a decanting sludge lagoon. At start up of the facility, the average influent flow had already approached the 80% capacity rate (1.2 MGD). This flow has been attributed to significant and increasing infiltration and inflow (I&I) from both the Windsor and Kodak collection systems as identified by current data and a previous I&I study performed by RTW. The existing I&I problems are currently being addressed by both the Town and Kodak. It is anticipated that I&I reductions of up to 25% can be realized. i Windsor WWTP Site Application 1-1 961188 Fort Collins Town of Windsor 39 Loveland Greeley 34 85 87 25 76 Boulder Denver• 70 Strasburg I s I 4 I I FIGURE 1-1 Regional Map Rotbberg, Tamburini & Winsor, Inc. 961188 ckip -too 4 ttfr 4-7 A LAKE Le t �own o'f indsor J _., APF! ��x' , cu�iaus 3 miles / / Q to I-251 • LIFT WASTEWATER %� -Th r� STATION L . on KODAK MVP 5 • WINDSOR WWTP 41 SITE 's i I E II FIGURE 1-2 Vicinity Map N Rothberg, Tambnrini & Winsor, Inc, 961188 Section one. Introduction Purpose The purpose of this report is to present the Application for Site Approval and supporting information to justify increasing the rated capacity of the Windsor wastewater treatment plant (WWTP) to 2.8 MGD. A completed Application for Site Approval is provided in Appendix A. The remainder of this report provides information integral to the Site Application. Section Two discusses the Windsor service area, wastewater flows and characteristics encountered at the treatment facility as well as those projected for the future. Section 3 presents the 208 Plan and review process. Section 4 is a brief discussion of the existing Windsor WWTP, its projected capacity and discharge limits. Section 5 summarizes the flood plain and natural hazards that may have an impact on the WWTP operation. Because the Windsor WWTP has only been operating since October, 1995, an additional report was prepared which evaluates historical operating and performance data from the Tri-Lakes WWTP in Monument, Colorado. The Tri-Lakes facility, which has been operating for approximately 4 years, is nearly identical in process components, size, and influent characteristics as the Windsor facility. This report entitled, "Reassessment of Treatment Capacity for the Tri-lakes and Windsor Wastewater Treatment Plants" accompanies this report and evaluates the treatment capacity of both the Tri-Lakes and Windsor facilities based on the Tri-Lakes operational and performance data, state design criteria for wastewater treatment plants, and the flows and loadings experienced by the two facilities. The evaluation concluded that both facilities should be re-rated to 2.8 MGD capacity (maximum 30-day average flow). I I Windsor WWTP Site Application 1-2 961188 SECTION 2 Wastewater Service Area, Flows, and Characteristics This section analyzes population and wastewater flow projections for the Windsor WWTP service area in order to determine the treatment plant capacity required for current and future flows. Wastewater characteristics and loadings are also presented in this section. Service Areas The Town of Windsor service area is shown on Figure 2-1. All wastewater produced within the service area is treated at the Windsor WWTP. Figure 2-2 is a five mile radius map of the area surrounding the plant showing nearby sanitation districts, sewage treatment plants, lift stations, and domestic water supply intakes where applicable. Habitable buildings within a one-mile radius, locations of potable water wells, as well as approximate topography is presented in Figure 2-3. A well list is included in Appendix B with the site application form. Current Population and Wastewater Flows Table 2-1 summarizes population and flow data for the Windsor area. Population data was provided by the Town of Windsor Planning Department. Wastewater flow data was derived from magnetic flow meter measurements taken at the wastewater lift station. One magnetic flow meter was used to measure raw sewage flow from the Town of Windsor and pretreated process wastewater from the Metal Container Corporation (MCC). A second magnetic flow meter measured the combined wastewater from the Town, MCC, and the Kodak plant prior to leaving the lift station. Wastewater flows from the Kodak plant were estimated by determining the difference in recorded I I Windsor WWTP Site Application 2-1 96118E ----1‘ x � 'r�4.c C...1 �'` �;y 4i�' §- sti (1 '._ A 1 J • _ ,� • • c. ../ •FEl ' - IV • • D IDS 40 • teen ed 04 J � ••- ' :fir d ii' ��. V Itt 1 ( !l Y, .. _ fit \. ._ --1 / TF�.Q#Ti�'A ff 1. I1T'��i> I /� r fi1F11t#hj °1 �:if 1 I __J 'ii!. 3 ' J r — . J' �� / ;+� ) 71 C / • • s' .1 • Cam • ® wi/ ^l "4f I• ii 1 •tilt, _ \ es u 17 �.� i � ; :St: .p� \�\ : S •-• i it v] In ' r i• r-�rryyr i / 111 ':. IWV• :•1•�Y(.1 )-. ZZ 4 r•%6' Y eNY Z rc£z/w 'Ned aro'!Sall 96118s stikpi1' .� .Si pi.il.,1C1•�Jlla ci /•/�a rmi//1//em.r a. ■C_=al- i _ • 1l ►ti 1 ea nun- . ■) - 1 C N r3 , txl _�1 a u.pi fS4411 R ie/ FIUI7 r=Js�aA_ • Pre �'' +p� : . itiiii .0 • ..- 1. ..t4—a . Ildre, 0 • - •4 I ft\di'''. 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O a ]C J ___'111!!!-J4 j lea • Iisi .0 :a E:INI— • . 04 • o tit CC I we I�ss111 ----.7. �rSI • m nE RI NQ p. yall.,.......".....?1 n - • �/j -q ./�3 • f a� �Yf t. J%� �bl • / 't a j G c i . . : .. . O ♦ / Jr •� I�IIII � - m / •l_ f/�. :.. t a•_��`°see�. :b 11) 11 h , M I Ill ! I J' /i • + Q'rCSI ,ie l v� CC D ej ' \ LJl • I /:' Sp �i. 70 / J "PB 1 1 .O . LL I •uQ N V lair bf- 2 O .5561 YZ tell, f69iNd TOM 'C1-Old 961188 Section two. Wastewater Service Area, Flows, and Characteristics flow between the two flow meters. Kodak contributes only domestic wastes to the Windsor WWTP. As shown in Table 2-1 the per capita flow has been as low as 127 gpd/person in 1995, and as high as 152 gpd/person in 1992. The average of the last three years is 136 gpd/person. Table 2-1 Population, Flow, and Flow Per Capita Data Year Population Town Annual Kodak Annual Total Annual Flow per Capita Average Average Flow' Average Flow (gpd/person)' Flow' (MGD) MGD 1990 5,062 0.76 0.08 0.84 148 1991 5,153 0.68 0.14 0.82 132 1992 5,319 0.81 0.11 .92 152 1993 5,600 0.81 0.2 1.01 145 1994 5,964 0.812 0.211 1.02 135 1995 6,510 0.826 0.285 1.11 127 Includes flow from the Town of Windsor and Metal Container Corporation(MCC) discharge. 2 Kodak flow determine by subtraction of the magnetic flow meter valves. ' Based on flow from Town. Does not include Kodak flow. August had the maximum average month flow for 1995. The August flow data is presented in Table 2-2. As indicated, the plant is currently operating near its present rated capacity of 1.5 MGD. Table 2-2 1995 Flow Data Town of Windsor Kodak Plant Total Flow and MCC Maximum Average Month Flow (MGD) 0.96 0.38 1.34 The relatively high per capita flows are due to significant infiltration and inflow (I & I) problems in the collection systems. These I&I problems are being aggressively addressed. Within the last six months, the Town of Windsor has replaced 2,200 feet of the interceptor line suspected of being the main source of I&I. The contractor working on one of the I&I projects verified that there was significant infiltration in the old line. Kodak is evaluating what actions can be taken to reduce the I&I occurring in its interceptors. There have been several meetings between the Town of Windsor and Kodak staff to discuss I&I reduction. Kodak 1 Windsor WWTP Site Application 2-2 1 Section two. Wastewater Service Area, Flows, and Characteristics has recently completed a study on their line which identified at least two significant sources of I&I. Kodak plans to eliminate these I&I sources by the end of 1997. As part of the most recent plant modifications, the magnetic flow meter used to measure the flow from the Town of Windsor and MCC was replaced by a Parshall flume (see Figure 4-1). Population and Flow Projections The population projections provided in Table 2-3 are based on an assumed flat line growth for the Town of Windsor of 200 building permits per year, and a density of 2.76 persons per building. The build- out values were received from the Town of Windsor Planning Department, the density is from the 1990 U.S. Census. A consultation with the Kodak Utilities Department in April, 1996, indicated that Kodak does not anticipate increasing the number of employees in the foreseeable future. Table 2-3 Projected Population and Flows Year Projected Projected Projected Kodak Total Projected Population Annual Average Annual Average Annual Average Flow' (MGD) Flow' Flow' 1995 6,510 0.826 0.285 1.11 2000 9,270 1.26 0.29 1.55 2005 12,030 1.64 0.29 1.93 2010 14,790 2.01 0.29 2.30 2015 17,550 2.39 0.29 2.68 2020 20,310 2.76 0.29 3.05 ' Except for 1995 which uses actual operating data, the annual average flow (QA) for each year is based on a constant flow of 136 gpd per capita. Q,,also incorporates the flow contributed by Metal Container Corporation. 2 The Kodak flow is assumed to be constant at 0.29 MGD. ' The total flow for each year includes the base flows for the Kodak facility, the MCC, and the Town. The average flow data for 1995 are based on measured flows. The projected flows assume that the Town of Windsor and Kodak will continue to take actions to reduce the infiltration and inflow (I&I) into their systems. The Kodak projected flows are maintained at the 1995 flow levels. This provides some conservatism in the projected flow values, as 1995 was a very wet year and high groundwater tables resulted in high I&I. If no control actions are taken, the I&I contribution to Windsor WWTP Site Application 2-3 961188 Section two. Wastewater Service Area, Flows, and Characteristics Kodak's flow may result in flows higher than those projected in Table 2-3. Wastewater Characteristics Almost all of the wastewater treated at the Windsor WWTP is from domestic sources. The Metal Container Corporation discharges approximately 0.07 MGD of pretreated industrial flow to the treatment plant which currently accounts for about 6% of total flow. The Kodak production facility operates their own lagoon system for treating their industrial process wastewater flow. Only domestic wastewater generated by the employees at the Kodak production facility is treated at the Windsor WWTP. It is anticipated that future wastewater characteristics will be similar to existing characteristics since build out of the area will be predominantly domestic dwellings. Wastewater flow data for each month of 1994 through 1995 were collected and analyzed for several relevant characteristics. These data are summarized in Table 2-4. Table 2-4 Influent Wastewater Characteristics (1994-1995) Parameter Average mg/L 90th Percentile mg/L Biological oxygen demand (BOD) 185 239 Total suspended solids (TSS) 153 211 Ammonia (NH,) 15.6' NA There were only 3 data points available for ammonia from the Windsor WWTP, the average of which is 15.6 mg/L. The maximum value was 21 mg/L. The anticipated loadings using the 90th percentile values and the design flow of 2.8 MGD is presented in Table 2-5. Table 2-5 Maximum Influent Loadings Parameter Maximum Projected Loadings 0 2.8 MGD BOD 5,581 lbs/day TSS 4,927 lbs/day 1 NH, 364 lbs/day I I Windsor WWTP Site Application 2-4 961188 Section two. Wastewater Service Area, Flows, and Characteristics A more complete discussion of the wastewater characteristics at the Windsor facility is presented in the "Reassessment of Treatment Capacity Study." i Windsor WWTP Site Application 2-5 961188 SECTION 3 Review of 208 Plan The Town of Windsor is located within the Cache la Poudre River drainage area. The drainage area drains the major portion of Northern Larimer County and the northwest portion of Weld Counties. The North Front Range Water Quality Planning Association (NFRWQPA) has prepared a draft update of the Areawide Water Quality Management Plan (208 Plan) for Larimer and Weld Counties. The draft refers to a study that is currently being initiated to investigate alternatives to cooperatively provide wastewater service to the region. One option which will be evaluated is a regional wastewater project located near I- 25 and the river to serve growth east of Fort Collins. The town of Windsor, along with Fort Collins, Timnath, Boxelder Sanitation District, South Fort Collins Sanitation District, and Larimer County are participating in the study. The study is scheduled to be completed in 1997. 1 Windsor WWTP Site Application 3-1 1 961188 SECTION 4 Treatment Facility Existing Facilities Wastewater Treatment Process The process sequence at the Windsor WWTP consists of preliminary treatment (screening and grit removal) followed by two parallel activated sludge basins, clarification, ultra-violet disinfection, and discharge to the Cache La Poudre River. An aerated biosolids storage lagoon with decanting capabilities is used for biosolids handling. A plant schematic is shown in Figure 4-1 and a Site Plan of the facility is shown in Figure 4-2. The plant headworks are located in the lift station building which is approximately one-half mile northeast of the main facility. The headworks includes screening equipment, degritting equipment, a Parshall flume, magnetic flow meter, and the wastewater transfer pumps. Raw sewage from the Town of Windsor, combined with process wastewater from the Metal Container Corporation, enters the lift station via a 24-inch main, and passes through a Parshall flume for flow recording. Process wastewater from the Kodak plant enters the influent wetwell via a 16-inch main. The combined raw wastewater is passed through an in channel grinder to remove large solids which could damage downstream equipment or interfere with treatment. The screenings are ground into smaller material and reintroduced into the influent raw sewage. The screened raw sewage flows into the grit basin where sand, gravel, cinders, and other particles which have settling velocities greater than those of the organic materials found in sewage are settled. Grit removal is provided to protect moving mechanical equipment from abrasion and abnormal wear and to reduce the quantity of deposits in channels and basins. The degritted raw sewage is then pumped through the magnetic flow meter where combined raw sewage flow is measured. The settled grit is collected and removed to landfill. I Windsor WWTP Site Application 4-1 961188 a a Is a 48 a a_o .a C3 = ►4 4 a r U 1x g ►4 ►4 mr it, Ect'g 5ds 5 04 04 ►4 N 1 11 04 co = i N f O Z m till g BO d ; 6c ,_ N o V 4 W U z 3 0 �.y ry J (.'! N(t L � .1114 ,:-.E, cn KO U O*1 IA �l o I W rniN J? � d LL • - -- --- -� .<_ V5 ttn< Ili o oh 18 c15 -o- 83 P 0 O y a C�z i PEE P CP�E I R, ; 1 maw -wr0O41 $0 ( •P661 ti WV OSOAQrams 9,10r Ya - 9l4 P 961188 II III CLARIFIER NO. 1 CLARIFIER NO. 2 '? - ^ AERATION VI'll BASIN NO. 1 III -- -.--r OPERATIONS BUILDING 24" EFFLUENT PIPEAERATION OPEN CHANNEL ih BASIN NO. 2 fj 1 k /a11 ' • H"--I LAGOON \ . ' '14: � SLUDGE � DISCHARGE • C40/ e. ". t'A . LAGOONSTORAGS POI RIVER �• \ P�U •\R�frei? \\ � �1 LIMITS OF • a FLOOD PLAIN \\ N • \ o a o ' .!' 1✓ ° PERIMETER FENCING i a-2 1 v. 1"=200' 12" FORCE MAIN FROM LIFT STATION I I I FIGURE 4-2 Site Plan 3 Rothberg, Tambnrini & Winsor, Inc. I t. 961188 Section four. Treatment Facility Following screening, grit removal, and flow measurement, the combined waste stream is pumped to a flow splitter box where the flow is directed to one aeration basin, or evenly split to the two parallel activated sludge process units. Secondary and nitrogen treatment is accomplished in the activated sludge process with fine bubble diffused aeration. The aeration basins are aerated using flexible sheath diffusers suspended uniformly across the basin. The diffusers are supported on weighted chains just off the bottom of the basins. Low pressure air is delivered to the diffusers by multistage centrifugal blowers. The oxygen concentration and mixing at various locations in the basins is controlled by adjusting the air flow to the individual aeration laterals. The laterals are activated or de- activated by automatic valves. Dissolved oxygen level in the basins is used to control the denitrification process. In the aeration basins, the biologically degradable organics in the sewage are utilized by microorganisms in the presence of oxygen to provide energy to the organisms, and the synthesis of more microorganisms, providing a substantial conversion of biochemical oxygen demand, BOD5, to organism cells. The basins can be divided into "aeration zones" allowing for areas to become oxic (with oxygen) and alternating anoxic zones (without oxygen). These alternating zones can be used to provide single-stage nitrification/denitrification. Aeration basin effluent flows by gravity to the secondary clarifiers. The activated sludge that is produced in the aeration basin is settled in the secondary (final) clarifiers. A part of the settled solids underflow (RAS) from the secondary clarifiers is returned to the aeration basins to maintain a high concentration of biologically active cells and to provide mixed liquor recycle for NO2-N conversion. Return activated sludge (RAS) from the secondary clarifiers is pumped back to the flow splitter box, where it is mixed with the influent waste stream and redistributed to the aeration basins. Alternatively, RAS can be pumped directly to the head of either aeration basin. Biological solids in excess of that needed to maintain the activated sludge inventory are "wasted" to the biosolids storage lagoon. Secondary clarifier effluent overflows a peripheral weir and launder and flows to the UV disinfection system. Effluent then passes through banks of UV lights which provides disinfection. The final effluent flows through a Parshall flume for flow measurement and is discharged to the Cache La Poudre River. Windsor WWTP Site Application 4-2 961188 Section four. Treatment Facility Solids Handling Process Materials captured in the mechanical bar screen are ground, then returned to the influent waste stream. Grit collected in the grit basin is mechanically removed and stored in a dumpster for disposal at the local landfill. Waste activated sludge (WAS) and scum from the secondary clarifiers is pumped to the biosolids storage lagoon. Although the biosolids lagoon is designed primarily for biosolids storage, the long holding time in the lagoon (43 to 143 days) will render the biosolids more inert, reduce the pathogen content, and decrease biosolids quantity. An air diffuser grid and a blower provides mixing and some aeration to the biosolids lagoon reducing potential odor problems. A decant facility allows for dewatering of the sludge lagoon to increase the solids content of the biosolids and reduce the overall sludge volume. Lagoon supernatant is pumped back to the headwork's flow splitter box where it is mixed with the incoming raw wastewater and RAS. Existing Facility Performance The Windsor facility has a limited amount of representative operational history since the modified facility began service in late October 1995. During the first three months of 1996, the Windsor facility final effluent BOD, TSS, and ammonia nitrogen averaged 6, 7, and 2 mg/L, respectively. Final effluent quality from the Tri-Lakes WWTP has also been excellent. Average annual effluent BOD, TSS, and total inorganic nitrogen (TIN) averaged less than 6, 4, and 4 mg/L in both 1994 and 1995. The maximum monthly flow at Tri-Lakes during 1994/1995 was 1.84 MGD and the maximum daily flow was 2.38 MGD. As the Windsor and Tri-Lakes plants are virtually identical in design, and as the Windsor facility has some operational advantages such as a significantly lower flow peaking factor, and warmer wastewater temperatures for most of the year, it is reasonable to expect that the Windsor facility is capable of meeting or exceeding the performance demonstrated by the Tri-Lakes facility. 1 Capacity at Recertification A discussion of each unit process and its capacity to handle 2.8 MGD of maximum month average flow is presented in the Recertification Study (see separate document). In summary, the study found: I Windsor WWTP Site Application 4-3 961188 Section four. Treatment Facility • Each secondary treatment train, consisting of an aeration basin and secondary clarifier, is capable of treating 1.4 MGD maximum monthly average flow. • The lift station in-channel grinder may require replacement with a larger unit when average daily flows exceed 3.7 MGD. • The magnetic flow meter measuring plant influent flows will need to be replaced when peak instantaneous flows approach 5 MGD. • Additional blower capacity will need to be added when peak day air requirements reach the existing firm air capacity. • Additional UV disinfection capacity will be added when peak plant flows reach 3.5 MGD. • RAS pumping capacity may not need to be increased. If the final RAS pumping capacity exceeds 1,000 gpm per pump, new RAS flow meters will be required. • All other unit processes are adequate to handle 2.8 MGD. Effluent Discharge Limits The Town of Windsor's wastewater treatment plant currently discharges under Colorado Wastewater Discharge Permit Number CO-0020320. The permit became effective on January 1, 1992 and will expire on December 31, 1996. The plant was permitted for a maximum 30-day average flow of 1.0 MGD. The recently completed plant modifications will, with approval of this site application, increase plant capacity to a maximum 30-day average flow of 2.8 MOD. A new discharge permit will be issued based on this site application and the additional plant capacity. Preliminary effluent limits have been calculated by the CDPHE based upon a 30-day maximum discharge flow of 2.97 MGD, the receiving stream classification, minimum monthly stream flows, stream temperature, and pH. These preliminary limits are compared to the current effluent limits in Table 4-1. As indicated, the most significant effluent limit changes are for total suspended solids (TSS), which will be reduced to a 30 mg/L monthly average, 45 mg/L weekly average, and for effluent ammonia (or inorganic nitrogen). The monthly ammonia limits will be reduced by a maximum of 44% (in May) with the most stringent limit of 1 Windsor WWTP Site Application 4-4 1 961188 Section four. Treatment Facility 9.8 mg/L occurring in June and July. The proposed limits can be readily met by the upgraded Windsor WWTP facility. Table 4-1 Windsor WWTP Existing and CDPHE Projected Effluent Limits Parameter I Existing Permit I Projected Limits I Permit Conditions Maximum flow, MGD 1.0 2.97 a BOD5, mg/L (lb/d) 30/45 30/45 b TSS, mg/L (lb/d) 75/110 30/45 b Fecal coliform, no./100 ml 6,000/12,000 6,000/12,000 e Total residual chlorine, mg/L 0.01 NA c pH, s.u. 6.5 to 9.0 6.5 to 9.0 d Oil and grease, mg/L 10 10 c Total ammonia or inorganic nitrogen' as N, mg/L January NA NA a February NA NA a March 19.9 12.7 a April 19.9 12.7 a May 24.3 13.5 a June 10.0 10.6 a July 10.2 9.8 a August 11.1 9.8 a September NA 12.0 a October NA 18.0 a November NA NA a December NA NA a * This is equivalent to the sum of total ammonia and total nitrite plus nitrate a 30-day average b 30-day average/?-day average c Daily maximum d Minimum-maximum e 30-day geometric mean/7-day geometric mean NA Not applicable 1 4 Windsor WWTP Site Application 4-5 961188 SECTION 5 Flood Plain and Natural Hazards The existing treatment facility site including aeration basins, sludge storage lagoon and clarifiers, has been raised above flood hazard level. In 1991, the Federal Emergency Management Agency gave the facility a Zone C designation, indicating an area which should only be subject to flooding by waters exceeding the 500-year flood level (Figure 5-1). The recently completed plant upgrades have maintained the same level of flood protection as indicated by the revised flood zone map in Figure 5-2. No plant impacts are expected due to flooding or flood plain issues. 1 1 Windsor WWTP Site Application 5.1 961188 a la lil +2t iy z trill. 7 + , ` , r o �'C.", +.u�. 3r 9'x'�'. N Z Z y{p�1�• d 10 CD 4e r% r.4:t%1 )J .ea M � Vw CD +l) tJ74 O f's� r ".t ' > C1','.N r, f 1Y aiS + �' rt �rit o 3 _ ern a4 ��'.� �/ "fin , ,41 r,Y IFT-�� h4 giS� �i�tf, ,ft � f 1 ,1! s 0 � -m I ?2f.rY ! �r iw5 N le ` t ia, � w . + a r Z X 114 Qm t .•,'Ai •i. - �.Q. cf, ., WI I. Lc' {II l� R•' y04 li 03 iir i ( N._ ^ ,. V 2 0\ ::, �j tjt'r%S2tit ib,r s G + !fit itit:, rW:1 _ !6� { • [7.'`+.'x...4 a.. N-tts . -�7"- ..-.._ ,•-•'"'"---..C''' h.''" �.F a a . a /i [[fit „ �` "- .�`?' A- r ,r,t 1244 Ms � `' Y Ohl '',41: -to.1.ec: �1 .t> \� 4 r , ,q ifr naTi ,.., , (-..v,4 b‘:;:it'"?.,"$i W %, r 1 I 4S Ii • vtYclti .... AS.:1"S`N + m} N +WI :',"x0rw)-.490 T •9EE+ Yd++d9 +69.t/F+ MAI APO l-S9+J 961188 a a >`,Zii M y % : I 1^� gld n t Y Y -41340 m9 } EY6 gib g; can ,p W ��" t aP yR x >, .23 az e,7 a -- T.C.• t,�t� %cwt'ata�•(Kt h YRf e \ q, T-�7„` Z _ r`fit W 3�1 i> 4 m i Ilk r � Fr r . 4.- z �rr $ *1 h`/a A c` T _ r- kt i(t r'�.�,.1� a`54, /l30 ar r (( 9(_‘,-;a1.,, a t5 a .: rw 3 �p .-Ftl? er- .1 a� ¢ U1 t} /Y C OrtET Pn7 nLi.3 t 11! ?w 3s v1,v- t >at ca r1 Oa pp;J'egc. ® fi5 a Y t Z N 2 / .¢�y� � . yy.. X15\<i..` ri' .h' ` � .'W' krx , j -�^ - y wm `^'•b"�� t1.,• Z Zit y / N V r \ z 1� I 4s e' fey • U �� +.ti �'y' / i _ a- T�1 `-. i N A • . Q d .&4-4. N I t :. � 1'F. <. +y't(�lts}iLb YT - - t'° �x y4 Y w , : L l ..7_4;tom- �' ✓7tt.. +n e�.�.s QI rr V'14,(41,,,- �v R�Y�+w �.4 /nom . . tn i .`rte .,Y - 4a •. \ \.. I iGa �. I m� ' h t N _ r r ]for p �: � �r{1cF.1r t e� CD I !r" t4.4 t+ r}vyfrriYrT-. W � ' Z oaf N I I KK,aA �} tfy{„z - N .wr ./.a0410-rra en •pest u pup roam rose sra a-ore 961188 APPENDIX A Application for Site Approval Form Windsor WWTP Site Application 961188 COLORADO DEPARTMENT OF HEALTH Water Quality Control Division 4300 Cherry Creek Drive South Denver, Colorado 80222-1530 APPLICATION FOR SITE APPROVAL FOR CONSTRUCTION OR EXPANSION OF: A) DOMESTIC WASTEWATER TREATMENT WORKS (INCLUDING TREATMENT PLANTS, OUTFALL SEWERS,AND LIFT STATIONS) OVER 2,000 GPD CAPACITY. B) INTERCEPTORS (IF REQUIRED BY C.R.S. 25-8-702 (3)) APPLICANT: Town of Windsor ADDRESS: 301 Walnut Street, Windsor, CO 80550 PHONE: (970) 686-7476 Consulting Engineer's Name and Address: Rothberg, Tamburini & Winsor, Inc., 1600 Stout Street, Suite 1800, Denver, CO 80202 PHONE: (303) 825-5999 A. Summary of information regarding new sewage treatment plant: 1. Proposed Location: (Legal Description) SE 1/4, SE 1/4, Section 34 Township T6N Range R67W , Weld County. 2. Type and capacity of treatment facility proposed: Processes used earth basin extended aeration activated sludge with mechanical clarifiers, UV disinfection. Hydraulic 2,800,00 Organic 7006 (4.0 MGD & 210 mg/L) gal/day lbs. BOD5/day Present PE 8.162' Design PE 16,912' % Domestic 94 % Industrial 6 see Attachment A 3. Location of facility: Attach a map of the area which includes the following: (a) 5-mile radius: all sewage treatment plants, lift stations, and domestic water supply intakes. (b) 1-mile radius: habitable buildings, location of potable water wells, and an approximate indication of the topography. 4. Effluent disposal: Surface discharge to water course Cache la Poudre Subsurface disposal N/A Land N/A Evaporation N/A Other N/A State water quality classification of receiving watercourse(s) Class 2 Recreation, Class 2 Warm Water Aquatic Life, and Agriculture Proposed Effluent Limitations developed in conjunction with Planning and Standards Section, WQCD: BOD5 30/45 mg/L SS 30/45 mg/L Fecal Coliform 6,000/12,000 /100 ml -1- WQCD-3 (Revised 8-83) 961188 Total Residual Chlorine 0.01 mg/L Ammonia 9.8 mg/L (most stringent monthly average) 5. Will a State or Federal grant be sought to finance any portion of this project? No 6. Present zoning of site area? Farming & Agricultural, Industrial Zoning with a 1-mile radius of site? Farming & Agricultural, Industrial 7. What is the distance downstream from the discharge to the nearest domestic water supply intake? No domestic intakes between site and confluence with South Platte River 13 miles downstream (Name of Supply) N/A (Address of Supply) What is the distance downstream from the discharge to the nearest other point of diversion? Jones Ditch, 10,000 ft downstream (Name of User) William Jones Irrigation Co., Greeley, CO (Address of User) 8. Who has the responsibility for operating the proposed facility? Town of Windsor 9. Who owns the land upon which the facility will be constructed? Town of Windsor (No new construction. Re-rating of facility capacity only.) (Please attach copies of the document creating authority in the applicant to construct the proposed facility at this site) 10. Estimated project cost: None at present time. Who is financially responsible for the construction and operation of the facility? Town of Windsor 11. Names and addresses of all water and/or sanitation districts within 5 miles downstream of proposed wastewater treatment facility site. See Attachment A (Attach a separate sheet of paper if necessary.) 12. Is the facility in a 100 year flood plain or other natural hazard area? Yes If so, what precautions are being taken? Plant site has been raised above flood hazard level. Has the flood plain been designated by the Colorado Water Conservation Board, Department of Natural Resources or other Agency? FEMA & CWCB (Agency Name) If so,what is that designation? Zone C, minimal flooding over 500 years 1 -2- WQCD-3 (Revised 8-83) 961188 13. Please include all additional factors that might help the Water Quality Control Division make an informed decision on your application for site approval. See attached report entitled, "Reassessment of Treatment Capacity for the Tri-Lakes and Windsor Wastewater Treatment Plants, April 1996." B. Information regarding lift stations: N/A 1. The proposed lift station when fully developed will generate the following additional load: Peak Hydraulic (MGD) P.E. to be served 2. Is the site located in a 100 year flood plain? If yes, on a separate sheet of paper describe the protective measures to be taken. 3. Describe emergency system in case of station and/or power failure: 4. Name and address of facility providing treatment: 5. The proposed lift station when fully developed will increase the loading of the treatment plant to % of hydraulic and % of organic capacity and agrees to treat (Treatment Agency) this wastewater? Yes No Date Signature and Title C. If the facility will be located on or adjacent to a site that is owned or managed by a Federal or State agency, send the agency a copy of this application. -3- WQCD-3 (Revised 8-83) 961188 D. Recommendation of governmental authorities: Please address the following issues in you recommendation decision. Are the proposed facilities consistent with the comprehensive plan and any other plans for the area, including the 201 Facility Plan or 208 Water Quality Management Plan, as they affect water quality? If you have any further comments or questions, please call 320-8333, Extension 5272. Date Recommend Recommend No Comment Signature of Representative Approval Disapproval 1. a• me t Agency 2. — � E (41 rnment: ' ities or Towns (If site is to w dory or within three miles) and t;tio Jiistricts. lt 3. 7hcI S ; ,Z7 -(t: r County mmissio rs 4. Oh n Wt� h thori 5. 7/7/9 City ounty Planning Authority 6. Council of Governments/Regional Planning 7. State Geologist (For lift stations, the signature of the State Geologist is not required. Applications for treatment plants require all signatures.) I certify that I am familiar with the requirements of the"Regulations for Site Applications For domestic Wastewater Treatment Works," and have posted the site in accordance with the regulations. An engineering report, as described by the regulations, has been prepared and is enclosed. DATE "Alpo X G' ✓ /[/�14/' iV. Wayne Millt'r Signature of Appl' ant TYPED NAME -4- 1 WQCD-3 (Revised 8-83) 961188 ATTACHMENT TO SITE APPLICATION In accordance with C.R.S. 1981, 25-8-702 (2)(a), (b), and (c), and the "Regulations for Site applications for Domestic Wastewater Treatment Works", the Water Quality Control Division must determine that each site location is consistent with the long range, comprehensive planning for the area in which it is to be located, that the plant on the proposed site will be managed to minimize the potential adverse impacts on water quality, and must encourage the consolidation of wastewater treatment works whenever feasible. In making this determination, the Division requires each applicant for a site approval for a domestic wastewater treatment works to supply an engineering report describing the project and showing the applicant's capabilities to manage and operate the facility over the life of the project to determine the potential adverse impacts on water quality. The report shall be considered the culmination of the planning process and as a minimum shall address the following: Service area definition including existing population and population projections, flow/loading projections, and relationship to other water and wastewater treatment plants in the area. Proposed effluent limitations as developed in coordination with the Planning and Standards Section of the Division. (Allow minimum four weeks processing time.) Analysis of existing facilities including performance of those facilities. Analysis of treatment alternatives considered. Detailed description of selected alternatives including legal description of the site,treatment system description,design capacities, and operational staffing needs. Legal arrangements showing control of site for the project life. Institutional arrangements such as contract and/or covenant terms for all users which will be finalized to accomplished acceptable waste treatment. Management capabilities for controlling the wastewater throughout and treatment within the capacity limitations of the proposed treatment works, i.e., user contracts, operating agreements, pretreatment requirements. Financial system which has been developed to provide for necessary capital and continued operation,maintenance,and replacement through the life of the project. This would include, for example, anticipated fee structure. Implementation plan and schedule including estimated construction time and estimated start-up date. Depending on the proposed project,some of the above items may not be applicable to address. In such cases,simply indicate on the application form the non applicability of those. -5- WQCD-3 (Revised 8-83) pp 961188 ATTACHMENT A Population Equivalent (PE) 1995 Recertification Maximum monthly average flow, QM 1.34 2.8 Annual average flow, QA 1.11 2.3 Ratio QM/QA 1.21 1.22 PE @ 136 gpd/person and QA 8,162 16,912 Names and addresses of all water and/or sanitation districts within 5 miles downstream of Windsor WWTP: City of Greeley 300 East 8th Street Greeley, CO 80631 (970) 350-9360 Hill and Park Sanitation District 1008 9th Street Greeley, CO 80631 (970) 352-8730 South Fort Collins Sanitation District 4700 South College Fort Collins, CO 80525 (970) 226-3104 • 961188 ATTACHMENT B Potable Water Wells Registered with the Colorado Division of Water Resources 1. Permit No. 35516; Eastman Kodak Co., Windsor, CO; permit issued 6/26/89; municipal and other uses 2. Applied for permit 11/16/90; Eastman Kodak Co., Windsor, CO; municipal & other uses 3. Permit No. 173537; Eastman Kodak Co., Windsor, CO; permit issued 6/10/93; municipal & other uses 4. Applied for permit 11/16/90; Eastman Kodak Co., Windsor, CO; municipal & other uses 5. Permit No. 173538; Eastman Kodak Co., Windsor, CO; permit issued 6/10/93; municipal & other uses 6. Permit No. 11456; H.V. Crumley, Windsor, CO; first used 5/25/62; domestic use 7. Permit No. 82024; H.V. Crumley, Windsor, CO; permit issued 12/4/75; domestic & livestock uses 8. Permit No. 124556; R.R. Anderson, Windsor, CO; permit issued 12/4/81; commercial use 9. Permit No. 147259; R.R. Anderson, Windsor, CO; permit issued 1/16/87; commercial use 961188 REASSESSMENT OF TREATMENT CAPACITY for the TRI-LAKES AND WINDSOR WASTEWATER TREATMENT PLANTS for the TOWN OF WINDSOR and WOODMOOR WATER AND SANITATION DISTRICT Rothberg, Tamburini & Winsor, Inc Professional Engineers and Consultants 1600 Stout Street, Suite 1800 Denver, Colorado 80202-3126 © 1996 RTW Project No. RO-2783-SC and RO-2890-SC } April, 1996 I I 961188 Contents Reassessment of Treatment Capacity for the Tri-Lakes and Windsor Wastewater Treatment Plants 1 Introduction 1 Physical Plant Comparison 3 Comparison of Wastewater Characteristics 5 Historical Plant Performances 8 Effluent Limits 9 Nitrification/Denitrification Requirements 10 Constant and Seasonal Inputs 11 Tri-Lakes WWTP Monthly Model Input Values 12 Aeration Basin Temperature 12 Aeration Basin pH 12 Ammonia Limit 12 BOD Concentration 12 Windsor WWTP Monthly Model Input Values 13 Aeration Basin Temperature 13 Aeration Basin pH 13 Ammonia Limit 14 BOD Concentration 14 Capacity of Treatment Unit Processes 14 Flow Estimates 14 1 Preliminary Treatment 15 Screenings 15 Tri-Lakes WWTP 15 1 Windsor WWTP 16 Grit Removal 17 Tri Lakes WWTP 17 1 Windsor WWTP 18 Flow Measurement 18 Influent 18 Tri-Lakes WWTP 18 Windsor WWTP 19 i Recertification Study for Tri-Lakes and Windsor WWTP's 961188 Flow Splitter Box 19 Tri-Lakes WWTP 19 RAS and WAS 19 Tri-Lakes WWTP 19 Windsor WWTP 20 Effluent 21 Tri-Lakes WWTP 21 Windsor WWTP 21 Transfer Pumps 21 Windsor WWTP 21 Activated Sludge Design Parameters 22 Return Activated Sludge (RAS) Pumping 22 Waste Activated Sludge (WAS) Pumping 24 Tri-Lakes 24 Windsor WWTP 25 Blowers 26 Tri-Lakes WWTP 26 Windsor WWTP 28 Secondary Clarifiers 30 Disinfection 31 Tri-Lakes WWTP 31 Windsor WWTP 33 Biosolids Digestion and Storage 34 Tri-Lakes WWTP 34 Windsor WWTP 35 I I I I I I Recertification Study for Tri-Lakes and Windsor VWVfP's ii 961188 Figures' Figure 1 Plant Schematics 1 Figure 2 Tri-Lakes and Windsor WWTP Flow Comparison 5 Figure 3 BOD Loadings at Tri-Lakes and Windsor WWTP's 5 Figure 4 Aeration Basin Temperature at Tri-Lakes and Windsor WWTP's 5 Figure 5 Tri-Lakes Projected Peak Day Air Requirements 28 Figure 6 Windsor Projected Peak Day Air Requirements 29 Figure 7 Tri-Lakes WWTP Chlorine Contact Basin 31 Figure 8 Fecal Coliforms vs. Contact Time—Tri-Lakes WWTP 1993-1995 31 Figure 9 Fecal Coliforms vs. Contact Time (Log Scale)—Tri-Lakes WWTP 1993-1995 31 Figure 10 Fecal Coliforms vs. Contact Time (Minutes)—Tri-Lakes WWTP 1993-1995 31 Figure 11 Fecal Coliforms vs. Chlorine Residual Tri-Lakes WWTP 1993-1995 32 1 I I All page numbers listed indicate the page directly preceding each figure. Recertification Study for Tri-Lakes and Windsor WWTP's iii 961188 Tables Table 1 Tri-Lakes WWTP Projected Flows at Re-Rated Plant Capacity 1 Table 2 Windsor WWTP Projected Flows at Re-Rated Plant Capacity 2 Table 3 Comparison of Original Plant Design Parameters 3 Table 4 Comparison of Plant Process Components 3 Table 5 Comparison of Influent Wastewater Flows and Loadings 6 Table 6 Wastewater Temperature at Tri-Lakes and Windsor 7 Table 7 Tri-Lakes WWTP Final Effluent Quality 8 Table 8 CDPHE Projected Effluent Limits for Tri-Lakes and Windsor WWTP Based on Indicated Effluent Flows 9 Table 9 Tri-Lakes Secondary Treatment System Nitrification Capacity and Operational Parameters' 13 Table 10 Windsor WWTP Secondary Treatment System Nitrification Capacity and Operational Parameters' 14 Table 11 Flows Used in Tri-Lakes and Windsor Recertification Evaluation 15 Table 12 Activated Sludge Design Parameters Compared to CDPHE Criteria 22 Table 13 Tri-Lakes WWTP 1995 Operational Data 23 Table 14 Tri-Lakes WWTP Estimated Waste Activated Sludge Production 24 Table 15 Aeration Blowers at Tri-Lakes WWTP 26 Table 16 Data Used to Determine Tri-Lakes Air Requirements 27 Table 17 Aeration Blowers at Windsor WWTP 28 Table 18 Values Used to Determine Monthly Air Requirements of Re-Rated Windsor WWTP 29 Table 19 Secondary Clarifier Evaluation 30 Table 20 Chlorine Contact Basin Detention Times at Tri-Lakes WWTP 31 Table 21 Chlorine Dosage Required at Projected Flow to Achieve CT*=15 33 I I Recertification Study for Tri-Lakes and Windsor WWTP's iv 961188 Reassessment of Treatment Capacity for the Tn-Lakes and Windsor Wastewater Treatment Plants Introduction This report is submitted in support of increasing the rated capacity of both the Tri-Lakes and Windsor wastewater treatment plants. The treatment capacity for both facilities is addressed in a single report because the plants are very similar, the same methodology was used in evaluating both facilities, and both evaluations relied on the four years of operating data from the Tri-Lakes WWTP. A flow schematic of the two facilities is shown in Figure 1. Our analysis indicated that the treatment plants will be able to adequately treat the projected flows shown in Tables 1 and 2 below. We are therefore, requesting that the Colorado Department of Public Health and Environment re-rate the capacities of both the Tri-Lakes and the Windsor WWTP's to 2.8 MGD. Table 1 Tri-Lakes WWTP Projected Flows at Re-Rated Plant Capacity Jan Feb Mar Apr May Jun Jul I Aug Sep Oct Nov Dec Annual Average Projected average 1.36 1.32 1.34 1.68 2.79 2.68 2.21 1.86 1.61 1.48 1.39 1.40 1.76 monthly flow, MGD Projected maximum 1.60 1.49 1.55 2.13 3.58 3.19 2.61 2.23 1.96 1.72 1.65 1.64 2.11 day flow, MGD l ` • I I IRecertification Study for Tri-Lakes and Windsor WWTP's 1 961188 0 a • 4 • 0 Ca Q 1 ... . a 4. N H • • INS a> u a 0 04 o cn z 04 104 vi a cle m 6 r R w am N N�I-R N3 w,->•-O F ¢ 3 • z H W P. C ♦ U WJ O S< eV 1 N U�� D isa yy/ JJ yy N \ y0 Oas - K V N •• U Zw N..— O•V r �"O�� re • z O U I I- 3 m I «a C/� 3H �o U ce 3 — p 0 T IZI W t U i .... Z CAPonll RI 11 P. I • r W I MOMUMEIJ CF2tEKK [gR U. - +voN 'V 2JX4r51-W f1£•966l '02 am 06g&W road 910 I-Old 961188 ' Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Table 2 Windsor WWTP Projected Flows at Re-Rated Plant Capacity Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average Projected average 2.04 1.81 1.99 2.00 2.28 2.60 2.68 2.77 2.46 2.23 2.36 2.36 2.30 monthly flow, MGD Projected maximum 2.13 2.08 2.04 2.12 2.69 2.87 2.82 3.02 2.82 2.34 2.60 2.52 2.50 day flow, MGD Plant flow capacities were determined by first identifying the flow and loading patterns present at the two treatment facilities. Then the operational periods (peak day, peak month, peak hour, etc.) which would be limited by existing plant equipment and processes were identified. Once the most restrictive flow periods were identified, the projected monthly flows at the re-rated capacity were determined using the annual flow patterns for the facility. Thus, it should be noted that the plant flow values shown in Tables 1 and 2 are not necessarily the maximum plant capacity for each month of the year. Instead, the flows in Table 1 and 2 are the expected monthly flows at the facilities which resulted from capacity limitations during some limited period of the year. The evaluations provided are reasonably conservative, especially in the case of Windsor where limited operational data for the newly constructed plant was available. Blower and pump capacities were not allowed to dictate final plant capacity. Additional pumping and blower capacity will be provided if firm capacities are reached during the life of the facilities. Instances when pump and blower capacity could potentially be limiting are discussed in the report. This report contains technical information and evaluations necessary to support these revised plant capacities. The report first compares the 1 similarities and differences in the design, loadings, and required effluent limits for the two facilities. Facility performance is discussed. Finally, the capacities of the unit process and equipment at each facility are I evaluated and the capacity limitations identified. Governing entities for the Tri-Lakes and Windsor WWTP are aware that regardless of rated plant capacity, the treatment plants are required to meet all conditions contained in their discharge permits. 1 I Recertification Study for Tri-Lakes and Windsor WWTP's 2 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Physical Plant Comparison Tables 3 and 4 compare the design parameters and process components for the Tri-Lakes and Windsor WWTP's. Both facilities were designed by Rothberg, Tamburini & Winsor, Inc. and are identical in most respects. The most significant differences related to plant capacity are lower blower and RAS recycle pumping capacities at Windsor WWTP, and the use of ultra-violet disinfection at Windsor verses the use of chlorine and sulfur dioxide at Tri-Lakes WWTP. Table 3 Comparison of Original Plant Design Parameters Design Parameters Tri-Lakes WWTP Windsor WWTP Average daily flow capacity, ID AVM 1.5 MGD 1.5 MGD Maximum period flow capacity, °,,,AK 2.4 MGD 2.1 MGD Peak hour flow capacity, °PEAK 5.8 MGD 5.0 MGD Total BOD5 (90th percentile), mg/L 400 mg/L 250 mg/L Total NH4 (90th percentile), mg/L 25 mg/L — Total Kjeldahl nitrogen, mg/L 40 mg/L 11 mg/L Total suspended solids, mg/L 400 mg/L — Table 4 Comparison of Plant Process Components Process Units I Tri-Lakes WWTP I Windsor WWTP 1 Preliminary treatment Screening • bar screens bar screens Type one manually cleaned (bypass), one manually cleaned, one 1 one mechanically cleaned overflow barscreen I (primary unit) Number 1 + 1 1 + 1 1 Grit removal Type square grit chamber square grit sump 1 Number 1 1 Dimensions 10'x 10' x 2'-0" deep (HWL) 2'-10" x 2'-1011x 3'-0" deep 1 Activated sludge system Lagoon Type earthen basin extended aeration earthen basin extended aeration INumber of trains 2 2 I 1 Recertification Study for Tri-Lakes and Windsor WWTP's 3 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Process Units Tri-Lakes WWTP J Windsor WWTP Basin dimensions 180' L x 100' W x 12' SWD 180' L x 100' W x 12' SWD at bottom Side slope 1.5 horizontal, 1 vertical 1.5 horizontal, 1 vertical Total volume at 2.1 mg/basin 2.1 mg/basin HWL Maximum RAS 900 GPM each basin 800 GPM each basin flow Blowers Type centrifugal centrifugal Number 3 4 Total SCFM 6,005 @ 5.35 psi discharge 4,550 @ 6.25 psi discharge O 95°F inlet) Firm capacity 3,585 @ 5.35 psi discharge 3,475 @ 6.25 psi discharge SCFM (D 95°F inlet) Secondary clarifiers Type center feed/perimeter overflow center feed/perimeter overflow with both rapid sludge return, with both rapid sludge return, bottom scraper return and scum bottom scraper return and scum removal removal Number 2 2 Diameter 50'-0" 50'-0" Side water depth 12'-0" 12'-0" Weir length 1,735 ft 1,735 ft Volume 176,243 gals 176,243 gals (neglecting slope) Return activated sludge pumping Type horizontal centrifugal horizontal centrifugal Number 3-1 per clarifier and 1 swing 3-1 per clarifier and 1 swing service service Flow 900 gpm each 800 gpm each Waste activated sludge pumping Type progressing cavity progressing cavity Number 3-1 per clarifier and 1 3-1 per clarifier and 1 swing/scum service swing/scum service Flow 80 gpm each 80 gpm each Disinfection Type chlorination/dechlorination ultraviolet (UV) I I Recertification Study for Tri-Lakes and Windsor WWTP's 4 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Process Units Tri-Lakes WWTP J Windsor WWTP Chlorine contact basin Number of units 1 (current), 1 (future) NA Size, ft 20 x 70 x 4 swd NA Volume, gallons 42,000 NA Sludge storage and decant Storage lagoon 8.9 mg 8.0+ mg volume NA = Not applicable Comparison of Wastewater Characteristics The influent wastewater characteristics of the Tri-Lakes and Windsor WWTP's were compared to provide a better understanding of the relative performance of the two facilities and to provide information for rating the capacity of the two facilities. Table 5 compares the annual average and peak monthly flows and influent BOD, TSS, ammonia and pH. Figures 2, 3, and 4 compare the monthly average flow, BOD loadings, and aeration basin temperatures of the two facilities. Based on the information presented, the following differences and similarities in wastewater flows and characteristics became apparent. 1. The 1995 annual average daily flows through the two facilities were quite similar; 1.156 MGD at Tri-Lakes and 1.113 \1GD at Windsor. 2. The Tri-Lakes facility showed much greater variation in monthly flows than did the Windsor facility. As indicated in Figure 2, the Tri-Lakes WWTP flows increased significantly during May and June. Maximum day flows as high as 2.38 and 2.25 MGD occurred in May and June 1995, respectively. In contrast, the Windsor 1 facility exhibited more moderate increases in monthly flow. In 1995, 1 the high flow period at Windsor lasted from May through September, but the peak daily flow never exceeded 1.5 MGD. 3. Tri-Lakes WWTP has higher influent concentrations and loadings ] than the Windsor facility. The Tri-Lakes influent BOD concentrations and loading were about 10 and 20% higher than at Windsor in 1994 and 1995, respectively. Tri-Lakes total suspended 1 solids were about 40% greater and influent ammonia appears to be 30 to 50% higher at Tri-Lakes, although very limited Windsor influent ammonia data was available. Recertification Study for Tri-Lakes and Windsor WWTP's 5 961188 d O - cn \ . -o z g < - O - o .§ K1 \ / / ` _� a / < \ -/ \ & .X t, _� / \ - / ` ` —< \ C » \ I / / \ . 6 < ! —< ; , r � r / u is ' -f i O \ —� \ \ � .:7- -/ \ a Z _ / - \ ej tit / (% o . o & / / \ 2 < < \ 2). -� 'a \ § < ii >- ` 5 1 2 . S - / ~ - E . -< _ k \- : q ! . Z L » -< CC | cep \ ^ \ \ C D %e* ! U- | : ; ; v » 961188 f..) ' O _ wt U _. O 'z - ............ O .............. J Q 1 ) a) Z ..C ....Y - D w Jo o Q C4 • 2m H )r::. — m . mQ — s_, m O cn I Z rn w U 0 rn a •'+, > = ct '• , HO Z N ..•�....x - O 3 f ................ .• Ir w _ _. . F U H .... H Q J U Z C Q O cc 2m - w M Z Q LLJ i Ct No c0 c0 d- 1— N O N N N r r r _ (P/41 ow.) 0O9 ebJl eAy LL f 9611813 j — \ C / . . 7 S \ / \ 6 _ 2 \ / ct P-i / / | \ • g• \ \ ® f \ \ \ c.. ' - c / / Ct ccs \ d C \ ccs e .2 2 ! > t \ _/ \ 0 | 6 p • _ 2 \ 3 | < & ` | 2 w = �/ - c - 2 ! / » w I - \ I ! / # | ` j w | inc‘i 0 r r b •Bea) @meama . 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's 4. Surprisingly, the winter aeration basin temperatures at the Windsor WWTP (elevation 4,740 feet) were generally colder than the aeration basin temperatures at the Tri-Lakes facility (elevation 6,850 feet) from October through February. See Figure 4 and Table 6. This may indicate that during winter, heat lost from the large aeration basins at night and during cold spells, is not regained during daylight or intermittent warmer periods. As would be expected, spring brings warmer water temperatures, more quickly to the lower plant (Windsor) and during July and August, aeration basin temperatures at Windsor were 5 to 6°C warmer at Windsor than at Tri-Lakes. An alternate explanation is that water temperatures in the Windsor lagoons were colder than at the Tri-Lakes aerated basins because longer holding times in the lagoons resulted in a greater heat loss to the environment, especially during the winter. This is substantiated by the significantly warmer aeration basin temperatures reported for the Windsor aeration basins in November and December 1995 vs. the November/December 1994 lagoon temperatures (Table 4). The Windsor treatment capacity evaluation in this report used the 1994 and 1995 Windsor lagoon temperature values. This provides a conservative estimate of treatment capacity, if as expected, aeration basin temperatures prove to be warmer than the lagoon data would indicate. Table 5 Comparison of Influent Wastewater Flows and Loadings Parameter Tri Lakes Windsor Data Review Period 1993- 1995 1994-1995 Average Flow, MGD 1993 0.788 - 1994 0.945 1.023 1995 1.156 1.113 Peak Day Flow, MGD 2.378 1.46 (month, year) (May, 1995) (August, 1995) Average Influent BOD, mg/L 1993 216 - 1 1994 214 177 1995 214 193 1 i Recertification Study for Tri-Lakes and Windsor WWTP's 6 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Parameter I In Lakes I Windsor Peak Day BOD, mg/L 308 348 (month, year) (December, 1995) (October, 1995) Average Influent TSS, mg/L 1993 235 — 1994 216 153 1995 220 153 Peak Day TSS, mg/L 451 319 (month, year) (August, 1993) (July, 1995) Average Influent Ammonia, mg/L 1993 25.24 - 1994 25.86 12' 1995 23.9 17.5 • Peak Day Ammonia, mg/L 33.5 21 ' (month, year) (December, 1994) (December, 1995) pH (range of monthly averages) Low 6.81 (July, 1995) 6.6 (December, 1995) High 8.7 (February, 1993) 8.5 (August, 1995) ' There were only three data points available for ammonia from Windsor WWTP: June, 1994 (12 1 mg/L), November, 1995 (14 mg/L), and December, 1995 (21 mg/L) • Table 6 Wastewater Temperature at Tri-Lakes and Windsor Month Tri-Lakes WWTP Average Aeration Windsor WWTP Average Effluent Basin Temperature °C Temperature °C 1 1994 1995 Average 1994 1995 Average January 6.1 6.7 6.4 4 5 4.5 1 February 5.9 7.3 6.6 5 7 6 March 8.1 8.6 8.35 11 10 10.5 1 I April 9.5 9.3 9.4 13 11 12 May 126 10.6 11.6 19 15 17 1 June 16.2 13.8 15 23 20 21.5 July 18.3 16.6 17.45 24 22 23 1 August 18.7 17.7 18.2 23 23 23 September 17.1 16.4 16.75 19 18 18.5 I Recertification Study for Tri-Lakes and Windsor WWTP's 7 361188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Month - Tri-Lakes WWTP Average Aeration Windsor WWTP Average Effluent Basin Temperature 'C Temperature °C 1994 1995 Average 1994 1995 Average October 14.2 13 13.6 11 13 12 November 10.0 10.5 10.25 8 13 10.5 December 7.8 8.1 7.95 7.9 13 10.45 Historical Plant Performances As shown in Table 7, final effluent quality from the Tri-Lakes WWTP has been excellent. Average annual effluent BOD, TSS and total inorganic nitrogen (TIN) averaged less than 6, 4, and 4 mg/L in both 1994 and 1995. The maximum monthly flow during 1994/1995 was 1.84 MGD and the maximum daily flow was 2.38 MGD. Furthermore, this high quality effluent was produced when only one aeration basin was in service. During 1994, the treatment plant operated using one aeration basin for approximately 9 months of the year, and in 1995 for approximately 7 months of the year. The Windsor facility has a limited amount of representative operational history since the modified facility began service in late October 1995. However, during the last two monthly reporting periods available (January and February 1996), the Windsor facility final effluent BOD. TSS and ammonia nitrogen averaged 8, 8, and 3 mg/L, respectively. As 1 the two Windsor and Tri-Lakes plants are virtually identical in desig,n. and as the Windsor facility has some operational advantages such as. a significantly lower flow peaking factor, and warmer wastewater 1 temperatures for most of the year, it is reasonable to expect that the Windsor facility is capable of meeting or exceeding the performance 1 demonstrated by the Tri-Lakes facility. Table 7 Tri-Lakes WWTP Final Effluent Quality Effluent Parameter Final Effluent Value { 1994 1995 I Flow, MGD Annual average 0.95 1.16 Maximum month 1.163 . 1.84 Maximum day 1.597 2.38 I Recertification Study for Tri-Lakes and Windsor WWTP's 8 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Effluent Parameter Final Effluent Value 1994 1995 BOD, mg/L Annual average • 5.0 5.4 Maximum month 8 10 Maximum day 10 11 TSS, mg/L Annual average 3.8 3.8 Maximum month 5.5 7 Maximum day 10 8 Total inorganic nitrogen, mg/L Annual average 2.8 3.8 Maximum month 5.6 7.1 Maximum day 13.6 8 Effluent Limits The expected effluent limits for the two facilities are shown in Table 8. The Tri-Lakes limits were calculated by the Water Quality Enforcement Division of the CDPHE based on a Tri-Lakes discharge of 3.2 MGI) and Donala WWTP discharges of 1.0 MGD. Both the Tri-Lakes WWTP and Donala WWTP discharge to Monument Creek and their relative and total contribution must be considered when calculating effluent discharge limits. Table 8 CDPHE Projected Effluent Limits for Tri-Lakes and Windsor WWTP Based on Indicated Effluent Flows 1 Parameter Tri-Lakes Windsor Permit Conditions Evaluated flow, MGD 3.2 2.97 a BODs, mg/L (Ib/d) 30/45 30/45 b TSS, mg/L (Ib/d) 30/45 30/45 b Fecal coliform, no./100 ml 2,345/4,690 6,000/12,000 e Total residual chlorine, mg/L 0.003 NA c pH, s.u. 6.0 to 9.0 6.5 and 9.0 d Oil and grease, mg/L 10 10 c 1 Recertification Study for Tri-Lakes and Windsor VV\A/TP's 9 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Parameter Tri-Lakes Windsor Permit Conditions Total ammonia or inorganic nitrogen* as N, mg/L January 20.5 76.7 a February 21.3 49.5 a March 23.1 12.7 a April 23.6 12.7 a May 19.6 13.5 a June 21.6 10.6 a • July 19.5 9.8 a August 19.8 9.8 a September 20.7 12.0 a October 17.8 18.0 a November 14.5 39.0 a December 24.5 61.3 a This is equivalent to the sum of total ammonia and total nitrite plus nitrate a 30-day average b 30-day average/7-day average c Daily maximum d Minimum-maximum e 30-day geometric mean/7-day geometric mean NA Not applicable, Windsor uses ultraviolet disinfection The expected effluent limits for the Windsor WWTP were estimated by the Water Quality Enforcement Division of the CDPHE based on a Windsor discharge of 2.97 MGD. • Nitrification/Denitrification Requirements In suspended growth nitrifying treatment systems, the aeration basin treatment capacity, and treatment capacity of the secondary clarifiers, is generally controlled by the concentration of mixed liquor suspended solids required to provide adequate nitrification of the wastewater. Nitrification rate is influenced by aeration basin temperature, pH, dissolved oxygen level and the final effluent ammonia concentration. RTW evaluated nitrification requirements for each WWTP using a 1 model which RTW developed. The model is based on accepted nitrification kinetic and stoichiometric principals. The nitrification model used the four parameters mentioned above, and other information, to calculate the sludge age, and ultimately, mixed 1 Recertification Study for Tri-Lakes and Windsor WWTP's 10 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's liquor suspended solid concentration required to meet the estimated future ammonia effluent limits. The allowable capacity of the secondary treatment system (aeration basins and secondary clarifiers) was determined by maintaining the mixed liquor suspended solids in the aeration basin below 3,500 mg/L, clarifier solids loading rate at or below 30 lb/sq ft/day, and the design safetyy factor between 10 and 25%. Evaluations were made on a monthly basis. In every case, the clarifier loading rate, rather than the mixed liquor concentration, controlled secondary system capacity. The model inputs which were used are discussed below. The constant and seasonal input values were used in the nitrification model for both the Tri-Lakes and Windsor facilities. Different monthly model input values were used for Tri-Lakes and Windsor due to differing operational conditions and available data at the two facilities. The model inputs for the two facilities are discussed below. Constant and Seasonal Inputs The following model inputs were kept constant or only adjusted on a seasonal basis: Yield (lbs biosolids / lbs BOD removed) was maintained at 0.875. Actual monthly yields averaged 0.72 lb/lb in 1995 with a maximum monthly value of 0.95 lb/lb. Return activated solids (RAS) recycle ratio was maintained at 1. Aeration basin dissolved oxygen was kept at 1 mg/L for all model runs. The anoxic fraction of the aeration unit was set at 25% from April through November and at 20% from November through March. Anoxic periods, which promote denitrification, are not needed to meet the proposed permit limits. However, clarifier suspended solids removal will be improved if denitrification is accomplished before secondary clarification. The aeration basin capacities were evaluated assuming that, overall basin aeration will be off 20 to 25% of the time to allow for denitrification to occur. A slightly higher anoxic fraction (25% instead of 20%) was used for the warmer months because denitrification in the clarifiers more readily occurs in warmer waters. 1 Recertification Study for Tri-Lakes and Windsor WWTP's 11 96118s Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Tri-Lakes WWTP Monthly Model Input Values The following model inputs were adjusted on a monthly basis when running the nitrification model. Aeration Basin Temperature The Tri-Lakes WWTP measures aeration basin temperature every 3 to 4 days. The 10th percentile temperature value (aeration basin temperature exceeds this value 90% of the time) was determined for each month using the January 1992 through December 1995 temperature values. These 10th percentile values were used in the model analyses unless an observed minimum monthly temperature for 1992 to 1995 was below the 10th percentile value. In those instances, the minimum observed temperature was used. Aeration Basin pH Tri-Lakes WWTP measures the plant influent pH on a daily basis. The lowest influent pH value for each month of 1995 was used in the model analyses. Ammonia Limit The preliminary ammonia nitrogen limits as calculated by the CDPHE based on a Donala WWTP discharge of 1.0 MGD were used for each month. BOD Concentration The Tri-Lakes WWTP analyzes for influent BOD on a weekly basis. Influent BOD concentrations have steadily increased since the Tri-Lakes WWTP was put into service in 1992. The highest BOD value reported for each month of 1992 through 1995 was used when running the model. The secondary system nitrification capacity based on the model inputs and ammonia limits described above are shown in Table 9. Also shown are the calculated sludge age, required mixed liquor suspended solids and clarifier solids loading rate for each month as determined by the model. I Recertification Study for Tri-Lakes and Windsor WWTP's 12 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Table 9 Tri-Lakes Secondary Treatment System Nitrification Capacity and Operational Parameters' Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Average flow, MGD 2.5 2.5 2.7 3.0 3.3 3.5 3.8 4.0 3.1 3.1 2.7 2.5 Design sludge age, days 14.6 15.4 13.5 12.5 10.1 7.9 7.0 6.0 107 11.0 12.8 14.3 Required MLSS, mg/L 2846 2864 2556 2288 2120 2034 1833 1742 2284 2289 2606 2366 Solids loading, lb/sq ft/day 30 30 29 29 30 30 30 30 30 30 30 30 Values determined using RTW Nitrification Model Windsor WWTP Monthly Model Input Values The following model inputs were adjusted on a monthly basis when running the nitrification model. Aeration Basin Temperature The Windsor WWTP measures aeration basin temperature five days a week excluding holidays. The 10th percentile temperature value (aeration basin temperature exceeds this value 90% of the time) was determined for each month using the January 1994 through December 1995 temperature values. These 10th percentile values were compared to the minimum monthly aeration basin temperature actually observed in 1994 and 1995, and the lowest value was used in the model analysis. l The one exception was February, where the minimum reported temperature for 1994 and 1995 was 4°C, but the 10th percentile temperature value was 1.42°. A value of 2°C was used for the Febn.ary 1 evaluation. Aeration Basin pH Windsor WWTP measures the aeration basin pH five days a week excluding holidays. The lowest effluent pH value observed in 1994 and 1995 (pH=6.6) was used in the model analysis. The pH occurred in December 1995, when complete ammonia removal with nitrification resulted in a pH drop to 6.6. The permit does not require ammonia removal in December, and pH 6.6 is viewed as a "worst case scenario." II Recertification Study for Tri-Lakes and Windsor WWTP's - 13 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Ammonia Limit The preliminary ammonia nitrogen limits as calculated by the CDPIIE based on a Windsor WWTP discharge of 2.97 MGD were used for each month (see Table 8). BOD Concentration The Windsor WWTP analyzes for influent BOD on a weekly basis. The highest monthly BOD value reported for 1994, and 1995, was used when running the model. The secondary system nitrification capacity based on the model inputs and ammonia limits described above are shown in Table 10. Also shown are the calculated sludge age, required mixed liquor suspended solids, and clarifier solids loading rate for each month as determined by the model. Table 10 Windsor WWTP Secondary Treatment System Nitrification Capacity and Operational Parameters' Jan Feb Mar I Apr I May I Jun I Jul I Aug I Sep I Oct I Nov I Dec Average flow, MGD NA NA 2.1 2.0 2.7 3.2 3.9 4.0 2.6 2.25 NA NA Design sludge age, days NA NA 30 26 17 11.5 8.0 7.3 13.8 19.5 NA NA Required MLSS, mg/L NA NA 3418 3474 2632 2151 1824 1711 2739 3134 NA NA Solids loading, lb/sq ft/day NA NA 30 30 30 29 30 29 30 30 NA NA Values determined using RTW Nitrification Model using pH=6.6 for all months. NA Ammonia removal not required Capacity of Treatment Unit Processes { Flow Estimates Table 11 shows the flows used in evaluating the Tri-Lakes WWTP capacity. Actual 1995 flow data was evaluated to determine the ratio of maximum month, 90th percentile maximum month and maximum weekly flow to the annual average flow. Actual 1993 through 1995 flow data was used to determine the ratio of the maximum day flow to the monthly flow. These ratios were used directly to determine projected flows based on a maximum monthly average flow of 2.8 MGD. The Recertification Study for Tri-Lakes and Windsor WWTP's 14 • 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's ratio of peak hourly, and peak instantaneous flows to peak day, and to annual average flow, using the 1995 data were lower than expected. Instead of using these ratios, more conservative peak hour flow and peak instantaneous flow values were used. The flows used in evaluating the Windsor WWTP were developed using the same methodology. The ratio of maximum month, 90th percentile maximum month, and maximum weekly flow to the annual average flow were determined using 1995 influent flow data. Actual 1994 and 1995 flow data was used to determine the ratio of maximum day flow to the monthly flow. These ratios were used directly to determine projected flows based on a monthly average flow of 2.8 MGD. As in the case of Tri-Lakes, the ratio of peak hourly and peak instantaneous flows to peak day, and to annual average flow, were lower than expected. Instead of using these ratios, a 5 MGD peak hour flow, and 5.5 peak instantaneous flow were used at Windsor, the same values as used at Tri-Lakes. Table 11 Flows Used in Tri-Lakes and Windsor Recertification Evaluation Tri-Lakes MGD Windsor MGD Maximum month average flow, QM 2.8 2.8 Annual average flow, °A 1.76 2.3 Maximum weekly average flow, Qw 3.43 2.9 Maximum day flow, Q, 3.58 3.05 90th percentile maximum month flow, Q, 3.68 3.07 Peak hour flow of maximum day, QH 5 '5 Peak instantaneous, Q, 5.5 5.5 Preliminary Treatment Screenings Tri-Lakes WWTP The Tri-Lakes WWTP has two bar screens, one mechanically cleaned, and one manually cleaned. The mechanically cleaned bar screen is used in daily operation and is designed for 5.8 MGD. The screen has bar spacing of/a' on center and is I Recertification Study for Tri-Lakes and Windsor WWTP's 15 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's oriented with a 75° slope with the horizontal. The interval/duration time set for the mechanically cleaned bar screen is adjustable and controlled through the PLC. The manually cleaned bar screen is used for bypass purposes only and is also designed for a flow rate of 5.8 MGD. The screen has bar spacing of on center and is oriented with a 45° slope with the horizontal. The channel approach to both screens provides a uniform flow cross section at the screen. The entire channel is accessible for observation and cleaning. Projected maximum month average flow is 2.8 MGD. At this flow rate the velocity at the manually cleaned bar screen is slightly less than 1 foot per second, and approximately 1.68 feet per second at the mechanically cleaned bar screen. These velocities meet the State velocity criteria for manually cleaned and mechanically cleaned bar screens at daily average flows (design velocity of 1 foot per second for manually cleaned screens, and a maximum of 2.5 feet per second for mechanically cleaned screens). The expected peak instantaneous flow is 5.5 MGD. Both bar screens are capable of handling projected average daily flows and peak instantaneous flows without additional improvements. Windsor WWTP The Windsor WWTP has one 'drop-in' manually cleaned bar l screen, and an in-channel grinder with overflow bar screen. The drop-in bar screen has bar spacing of approximately 11/2" on center, is oriented with a 90° slope with the horizontal, and is used only when the in-channel grinder is out of service. The in- ! channel grinder is operated continuously through an operator determined interval/duration timer. A manually cleaned bar screen is also provided at the old Town and Kodak influent entrances to the Lift Station/Headworks. These bar screens are manually cleaned and are used only during emergency bypass conditions. f The channel approach to the screen provides a uniform flow cross section at the screen. The entire channel is accessible for observation and cleaning. 1 Recertification Study for Tri-Lakes and Windsor WWTP's 16 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Projected maximum month average flow is 2.8 MGD. At this flow rate the velocity at the drop-in manually cleaned bar screen is approximately 0.67 feet per second. This velocity meets the State velocity criteria of 1 foot per second for a manually cleaned bar screen at daily average flows. The in-channel grinder with overflow bar screen is designed for a flow rate of 3.7 MGD. At this flow rate, should the drop-in screen be required due to grinder servicing, the velocity at the screen would be approximately 0.9 feet per second. The screening and grinding equipment is capable of handling projected average daily flows without additional improvements. When average daily flows exceed 3.7 MGD the in-channel grinder may require replacement with a larger unit. Grit Removal Tri Lakes WWTP Grit removal is accomplished using a 10 foot square grit settling basin with scraper system. Influent deflector fins located upstream of the grit collector equally distribute and slow the flow prior to entering the grit chamber. A rotating mechanical scraper moves the settled grit into the grit sump where it is pumped to the sludge storage lagoon using one of two grit pumps. The CDPHE design criteria for a channel-type grit chamber is "to provide controlled velocities, applied over the entire flow range, as close as possible to 1 foot per second" and to consider "undesirable turbulence and velocities at inlets and outlets." At the Tri-Lakes facility, the flow velocity through the grit chamber will be approximately 0.14 ft/sec at the projected annual average flow of 1.76 MGD with a detention time of 73 seconds. At the projected peak hour flow of 5 MGD the velocity through the grit chamber will be approximately 0.4 ft/s with a detention time of 26 seconds. The low flow velocity through the Tri-Lakes grit chamber helps to mitigate influent and effluent turbulence which could adversely effect settling in the chamber which is only ten feet in length. Any excessive organic material which may settle with the grit is pumped along with the grit to the sludge storage lagoon. The Tri-lakes facility has no primary settling, and the removal of some heavier settleable organic material in the grit 1 Recertification Study for Tri-Lakes and Windsor WWTP's 17 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's chamber may be beneficial by preventing subsequent deposition of the material in the aeration basins. The existing grit removal basin and ancillary pumping equipment have adequate capacity to handle the projected flows and grit loadings. Additional equipment is not required for projected future flows. Windsor WWTP Grit removal at the Windsor WWTP is accomplished using an in- channel grit sump and manually operated grit pump. Grit in the raw wastewater settles out in the grit sump as it passes through the influent channel. Periodically the grit is pumped by a recessed impeller grit pump to the grit collection box. The collected grit is dewatered via a mesh bottom on the collection box that drains back into the influent channel. Grit is dumped into a waste hopper located adjacent to the building and removed to landfill with other industrial waste. Due to the typically low grit content in the raw wastewater it is not anticipated that additional grit removal capacity will be required at higher flows. Flow Measurement Flow measurement is provided at various locations throughout the treatment facilities, including influent, RAS, WAS, and effluent flows. Each flow measuring location is presented below. Influent Tri-Lakes WWTP The headworks is equipped with a 12-inch Parshall flume for measuring influent flow. Instantaneous flow is measured by a staff gauge. The hydraulic capacity of the 12-inch flume is 10 MGD. Flow recording is currently not available. The capacity of the Parshall flume is adequate for projected ]' future flows. Although flow recording is not available at the 1 Recertification Study for Tri-Lakes and Windsor WWTP's 18 X1.188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's influent, effluent flow recording is available. No additional improvements for influent flow measuring will be required for projected future flows. Windsor WWTP A 12-inch Parshall flume upstream of the bar screen in the influent channel is used to measure raw sewage flow from the Town of Windsor. Wastewater from the Town and the Kodak plant is combined and measured using a 10-inch magnetic flow meter prior to leaving the Lift Station/Headworks. The hydraulic capacity of the 12-inch Parshall flume is 10 MGD. The flow rate is displayed locally. The magnetic flow meter has a capacity of 5 MGD. The flow rate from the magnetic flow meter is displayed locally and is also transmitted to the plant where it is indicated, recorded, and totalized. In order to accommodate projected peak instantaneous flows, the magnetic flow meter will require replacement. No other additional improvements for influent flow measuring and recording will be required for projected future flows. Flow Splitter Box Tri-Lakes WWTP and Windsor WWTP • The flow splitter box design is identical for the two treatment plants. Wastewater influent is split between two aeration basins in an upflow weir split box. Equal flow division is accomplished by weirs which have equal lengths and equal crest elevations. An air line is supplied to the bottom of the upflow tube to insure movement of solids through the tubes and to prevent deposition. No additional improvements will be required for projected future flows in either facility. RAS and WAS Tri-Lakes WWTP Flow measuring is accomplished using a magnetic flow meter on each of the RAS and WAS lines. Flow recording is accomplished I Recertification Study for Tri-Lakes and Windsor WWTP's 19 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's in the PLC on a continuous basis. Totalized flows are determined through PLC logic and are accessible from the PLC. The capacity of the Tri-Lakes RAS meters is 1,200 gpm. There is one meter for each of the two aeration basins. The existing firm RAS pumping capacity for each aeration basin is 900 gpm. Therefore, the existing RAS meter has adequate metering range. If additional RAS pumping capacity is provided beyond the 1200 gpm range (see discussion on RAS pumping), a higher range RAS meter will be required. The capacity of the Tri-Lakes WAS meter is 250 gpm. The Tri- Lakes WWTP has three WAS pumps with an individual maximum capacity of 80 gpm. Firm pumping capacity (two pumps operating, one standby) is 160 gpm. Projected maximum WAS pumping requirements are 167 gpm at re-rated plant capacity (see discussion on WAS pumping). Therefore, the existing WAS meter has adequate capacity for WAS flows at t re-rated plant capacity. Windsor WWTP Flow measuring is accomplished using two 6-inch magnetic flow meters on the RAS lines and one 4-inch magnetic flow meter on the WAS line. The flow rate from either RAS mag meter is displayed locally and is also transmitted to the PLC. The flow rate and totalized flow for the WAS mag meter is displayed locally. The capacity of each Windsor RAS magnetic flow meter is l,1100 I gpm. There is one meter for each of the two aeration basins, The existing firm RAS pump capacity for each aeration basin is 800 gpm. Therefore the existing RAS meter has adequate metering range. If additional RAS pumping capacity is provided beyond the 1,000 gpm range (see discussion on RAS pumping), a higher range RAS meter will be required. The capacity of the Windsor WAS meter is 200 gpm. The Tri- Lakes WWTP has three WAS pumps with an individual maximum capacity of 80 gpm. Firm pumping capacity (two pumps operating, one standby) is 160 gpm. Projected maximum WAS pumping requirements are 157 gpm at the re-rated plant capacity (see discussion on WAS pumping). Therefore, the 1 Recertification Study for Tri-Lakes and Windsor WWTP's 20 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's existing WAS meter has adequate capacity for future WAS flows at the re-rated plant capacity. Effluent Tri-Lakes WWTP Effluent flow is measured using a 12-inch Parshall flume after disinfection. The hydraulic capacity of the flume is 10 MGD. Flow recording is accomplished using an electronic sensor, the signal of which is sent back to the PLC for totalizing. No additional improvements to the effluent flow metering and recording equipment is required for projected future flows. Windsor WWTP Effluent flow is measured using a 9-inch Parshall flume as the primary device with a capacitance probe as the secondary device. Flow rate is indicated, recorded, and totalized locally. The capacity of the flume is 10 MGD. No additional improvements to the effluent flow metering anc. recording equipment is required for projected future flows. Transfer Pumps Windsor WWTP The Windsor WWTP has three transfer pumps to pump preliminary treated wastewater from the lift station/headwork,, to the flow splitter box. The pumps are sized for 1,500 gpm each (6.48 MGD total capacity). No additional improvements to the transfer pumps are required for projected future flows. I Recertification Study for Tri-Lakes and Windsor WWTP's 21 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's . Activated Sludge Design Parameters Table 12 evaluates the activated sludge system design parameters at the re-rated plant capacities for the Tri-Lake and Windsor WWTP's compared to the requirements contained in Table H-1 of the CDPHE Design Criteria. As illustrated, all design criteria are satisfied. Table 12 Activated Sludge Design Parameters Compared to CDPHE Criteria Flow Average Average Space Average Average Design Aeration Time Loading MLSS Conc. Loading Factor Recycle Range MGD (hrs) lbs. GODS (mg/L) lbs. BODS Or 1,000 cu. ft./day lb. MLVSS/day a CDPHE design 24 <25 2,000 to 6,000 0.05 to 0.2 0.25 to 1.50 criteria for extended aeration Tri-Lakes WWTP Annual average 1.76 57 8.1 1,742 to 2,866 0.08 (maximum) 0.25 to 1.47 flow (2 pump;) Maximum month 2.8 36 12.8 1,742 to 2,866 0.12 (maximum) 0.25 to 0.33 average flow (2 pumps) Windsor Annual average 2.3 44 9.5 1,500 to 3,474 0.10 (maximum) 0.25 to 1.0 flow (2 pump) Maximum month 2.8 58 11.6 1,500 to 3,474 0.12 (maximum) 0.25 to 0.32 average flow (2 pumps) Return Activated Sludge (RAS) Pumping The Tri-Lakes WWTP 1995 monthly RAS recycle ratios are shown in Table 13. As indicated, the maximum monthly recycle ratio was 1.0 in December 1995 and the average 1995 recycle rate was 0.72. Two years (1994 and 1995) of daily operational data was evaluated to better define the RAS recycle rate used at the Tri-Lakes facility. This evaluation found the plant operated at a RAS recycle of 0.84 or less, more than ninety percent of the time. i iRecertification Study for Tri-Lakes and Windsor WWTP's 22 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Table 13 Tri-Lakes WWTP 1995 Operational Data Parameter Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Average RAS recycle 0.48 0.49 0.53 0.51 0.60 0.73 0.85 0.89 0.93 0.72 0.89 1.01 0.72 ratio Yield 0.76 0.75 0.74 0.95 0.83 0.69 0.64 0.61 0.82 0.80 0.67 0.63 0.74 lb solids/lb BOD The operating RAS ratio is a function of sludge settleability, compactability, desired sludge concentration, desired blanket depth and removal efficiency of the sludge collection system. Typical operating values are 0.3-0.8 for most systems. The RAS recycle ratio requirements at Tri-Lakes and Windsor are expected to be within this range. Both plants have a rapid return type sludge collection system which is more efficient at capturing settled solids in the clarifier than conventional systems, thereby reducing the volume of recycle RAS flow required. Secondly, both systems are designed to denitrify in the aeration basin. This eliminates poorly settling sludge due to denitrification in the • secondary clarifiers. State design criteria require a RAS recycle range of 0.25 to 1.5. The Tri-Lakes WWTP has three RAS pumps with 900 gpm capacity each at 26 feet of rated head. At the average annual flow rate of 1.76 MGD, two pumps (firm capacity) would provide a maximum available RAS recycle ratio of 1.47. At the maximum monthly plant flow of 2.8 MGD, two pumps can attain a maximum RAS recycle ratio of 0.92. Additional RAS recycle capacity can be added by changing the impellers in the RAS pumps and switching to larger motors. This will be done at Tri-Lakes if operational experience indicates that higher recycle rates are required. The Windsor WWTP has three RAS pumps, each with 800 gpm capacity at 24 feet of rated head. At the average annual projected flow rate of 2.3 MGD, two pumps would provide a maximum available RAS ratio of 1.0. At the maximum monthly plant flow rate of 2.8 MGD, two pumps can attain a•maximum RAS recycle ratio of 0.82. Recertification Study for Tri-Lakes and Windsor WWTP's 23 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's The capacity of the RAS pumps at Windsor will be increased by changing impellers and switching to larger motors if plant operation indicates that higher RAS recycle ratios are beneficial. Waste Activated Sludge (WAS) Pumping Tri-Lakes The 1995 monthly solids yield factors were evaluated for the T ri- Lakes WWTP and are summarized in Table 13. As indicated, the annual average yield factor was 0.74 pound solids/ pound BOD removed and the maximum monthly average was 0.95 which occurred in April. Three scenarios were evaluated to estimate the waste activated solids production for the Tri-Lakes WWTP at plant capacity (Table 14). The first scenario used the maximum day flow (3.58 MGD), highest influent BOD value reported for 1995 (308 mg/L), and a sludge yield factor of 0.875 (18% safety factor over annual average) to determine WAS quantities for rated plant capacity. Table 14 Tri-Lakes WWTP Estimated Waste Activated Sludge Production Period Scenario 1 Scenario 2 Scenario 3 General April May Maximum day flow, MGD 3.58 2.13 3.58 Influent BOD, mg/L 308 220 229 Yield, lb solids/lb BOD 0.875 0.95 1.15 Total WAS, lbs/day 8047 3713 7863 Required pumping rate, 167 77 163 gpm The second scenario looked specifically at the month of April which had the highest yield factor in 1995. April WAS volume was calculated using the highest reported influent BOD value for April at Tri-Lakes (220 mg/L), the projected maximum April flow at plant re-rated capacity (2.13 MGD), and the 0.95 yield factor. As indicated in Table 14, the required pumping rate was significantly below that calculated for scenario 1. 1 - i Recertification Study for Tri-Lakes and Windsor WWTP's 24 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's A third scenario looked at the month of May. The May plant influent flows have been historically the highest compared to other months, so May represents the month most likely to first reach rated plant capacity of 2.8 MGD. May WAS volume was calculated using the highest reported influent BOD value for May at Tri-Lakes (229 mg/L), the maximum daily flow (3.58 MGD), and a solids yield factor of 1.15. The yield factor , which is likely an anomaly, was calculated based on the May 1994 Tri-Lakes operational data. WAS concentration was assumed to be 4000 mg/L for all scenarios. As indicated in Table 14, the maximum required WAS pumping rate is 167 gpm on a 24 hour basis. The Tri-Lakes facility has three progressive cavity pumps, which, by changing the sheaves and belts, have a total capacity of 160 gpm. This capacity is believed to be adequate as the maximum projected pumping rate of 167 gpm is based on the maximum influent BOD concentration and annual maximum daily flow occurring on the same day. This is an unlikely occurrence at Tri-Lakes where maximum flows are related to ground water infiltration. Windsor WWTP A similar methodology was used to estimate waste activated sludge production at the Windsor WWTP. No solids yield data was available from Windsor so the 0.875 value used for Tri-Lakes was assumed. The projected peak day flow and the highest reported influent BOD value for each month were used to calculate a maximum monthly WAS production value. The minimum WAS concentration was assumed to be 3000 mg;'L. This is lower than the WAS concentration value at Tri-Lakes. because Windsor does not have to nitrify from November through February and may choose to carry lower mixed liquor solids during this period. Based on this analyses, September had the highest projected WAS production, resulting in a required pumping rate of 157 gpm. The estimated peak day flow for September was 2.82 MOD and estimated highest BOD was 274 mg/L. The Windsor WWTP has three progressive cavity pumps each with an individual capacity of 80 gpm at the rated head. The maximum projected WAS pumping requirements can be met 1 Recertification Study for Tri-Lakes and Windsor WWTP's 25 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's using two of the existing WAS pumps with the third remaining as standby. Blowers Tri-Lakes WWTP The Tri-Lakes WWTP has three blowers, one 75 hp and two 125 hp, to provide air to the two aeration basins located at the facility (See Table 15). In 1995, the Tri-Lakes WWTP successfully treated an annual average flow of 1.16 MGD and maximum monthly flow of 1.84 MGD using only the 75 hp blower. Intuitively, the existing 150 hp of additional blower capacity should provide adequate aeration to meet the re-rated plant capacity of 1.76 MGD and 2.8 MGD maximum month. This direct comparison is somewhat misleading. Influent BOD concentrations are expected to increase in the future. Also, in 1995, the Tri-Lakes facility generally fully nitrified and denitrified, which it will not have to do to meet present and future effluent limits. A more detailed blower evaluation was deemed necessary and is provided below. Table 15 Aeration Blowers at Tri-Lakes WWTP Number of Manufacturer—Model Motor HP Rated Capacity Blowers at 5.35 psi discharge SCFM 1 Lamson-850 Series 75 1,165 2 Lamson-860 Series 125 2,420 Tri-Lakes aeration basin air requirements were evaluated by the comparing the theoretical average monthly aeration basin air requirements for 1995 to the actual amount of air supplied by the blowers, adjusting the diffuser alpha fouling factor to compensate for the difference between the theoretical and actual air requirements and then using the adjusted alpha factor value in the calculation of air requirements at the re-rated plant capacity. The observed alpha factor was calculated for every month of 1995. The resultant monthly diffuser alpha fouling factor values ranged from 0.27 to 0.39, with an average value of 0.34. Aeration requirements at the re-rated plant capacity peak daily flow (3.58 i Recertification Study for Tri-Lakes and Windsor WWTP's 26 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's MGD) were then determined by using the projected "worst case" monthly BOD, ammonia and basin temperature values as well as the 0.34 alpha fouling factor. The approach used for determining air requirements is quite conservative but also takes advantage of available plant operation history. The specific data used in determining the diffuser alpha fouling factor and estimated air requirements are summarized in Table 16. Table 16 Data Used to Determine Tri-Lakes Air Requirements Values Used to Determine Observed Diffuser Alpha Fouling Factors Flow rate Monthly average (MGD) BOD, removal Monthly average (mg/L) Ammonia conversion Monthly average (mg/L) Nitrate removal Monthly average (mg/L) Aeration basin dissolved Monthly average (mg/L) oxygen Aeration basin Monthly average (CC) temperature Ambient air temperature Average of daily minimum and maximums ('F) Solids yield Monthly average (lbs sludge/lb BOD removed) Blower SCFM Monthly average of ampere values read off 75 hp blower and then converted to SCFM (standard cu ft/minute) Values Used to Determine Monthly Air Requirements of Re-Rated Tri-Lakes Flow rate Projected peak day flow (MGD) BOD, removal Maximum historical influent BOD concentration 1992-1995 (mg/L) Ammonia conversion Maximum historical influent concentration minus permit limit (mg/L) • Nitrate removal Assumed to be zero (mg/L) Aeration basin dissolved 1 (mg/L) oxygen Aeration basin 90th percentile (highest) value (`C) temperature Ambient air temperature Highest 1995 daily temperature in month (-F) Solids yield 1995 monthly average (lb sludge/lb BOD removed) Blower SCFM Calculated from above 1 Recertification Study for Tri-Lakes and Windsor WWTP's 27 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Figure 5 compares the projected peak day monthly aeration requirements against the 6005 SCFM rated capacity of the three existing blowers. As indicated, the three Tri-Lakes blowers have adequate capacity to handle the projected flows and loadings. Figure 5 also compares the 3,585 SCFM firm capacity of the blowers (one 125 hp blower out of service) against the projected peak daily air requirements. As indicated, the existing blowers do not have enough firm capacity to provide adequate air if one of the 125 hp blower is non-functional. In order to provide adequate aeration capacity, the Tri-Lakes WWTP will add a third 125 hp blower when peak day air requirements reach the firm air capacity of 3,585 SCFM. Windsor WWTP The Windsor WWTP has four blowers, one 40 hp, one 75 hp and two 100 hp, to provide air to the two aeration basins located at the facility (See Table 17). As the modified Windsor facility began operations in late October 1995, there was insufficient operational history to do the detailed performance analyses which was done for the Tri-Lakes facility. Instead, the alpha fouling factor, soluble oxygen transfer efficiency, and other aeration system parameters which were used in matching the theoretical and actual air requirements in the Tri-Lakes system were used to determine aeration requirements at the Windsor facility. This was considered a valid approach since the Tri-Lakes and Windsor WWTP's use identical Biolac aeration systems under similar loading conditions. Table 17 Aeration Blowers at Windsor WWTP Number of Manufacturer—Model Motor HP Rated Capacity at 6.25 Blowers psi discharge, SCFM 1 Lamson-510 Series 40 650 1 Lamson-810 Series 75 1,100 2 Lamson-850 Series 100 1,725 Evaluation of aeration requirements at the Windsor facility parallelled the methodology used for Tri-Lakes. A maximum projected aeration requirement was calculated for every month. A diffuser fouling factor value of 0.34 was used in the analyses and the "worst case" monthly BOD and basin temperature values I Recertification Study for Tri-Lakes and Windsor WWTP's 28 961188 U Cl J ;_-,- 0 E V Q E cit 111.111111,814.,. z 45 E— a) isz O zr3 ro 'r, r ,TgS.,a;;3;�;�P ... U) L' T ............ E 4-4 ,yZ '3 ryb y> N� C To.. E a) a <:,:g;;.yaiys.�eyi;„i;yi:i..e '.9:y}Q; ;: jZ9:QR«!:yRu!ev@>.ay;e .':i � Y�....fi� 4 � .: 9� ':' �`�i§i§RR,i..L��ib R S� b N P4 t .. c D CZ E s i: ::: a:i:z:,:, icvcs::: :::::a'i:a.;r»» r'1-Nlitib:E:i.: N .�:...'.::.:..............:::.�........:.:.... a.....:,::.:n..ab:Rn:i...n,.:n:.:.di::i:)i;i:}i:R:;:E:i:::^::e:;. :..... 1 a ,—' U \kE Q W Q cE' cn •;--, enb\ TTTNJ V/ .. w d ct E co 2 T.: u L ao -Q c a) -- .r, ass r a s 6 z , u- c W 1 O O O O O O O O O O O (3 O O O Oto 0 in CD O O O O O O O 0 Ce LO CO CO N N 1— I 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's were used. There were only six influent ammonia concentrations measured on the Windsor plant influent, and the highest, 31 mg/L was used for every month of the year. The analyses assumes that the monthly peak day flow, peak influent BOD, peak ammonia and highest aeration basin temperature will all occur on the same day. The evaluation thus provides a conservative estimate of the maximum air requirements. The specific data used to determine Windsor's estimated air requirements when the plant reaches its re-rated capacity are shown in Table 18. Table 18 Values Used to Determine Monthly Air Requirements of Re-Rated Windsor WWTP Flow rate Projected peak day flow (MGD) BOD, removal Maximum historical influent BOD concentration 1994-1995 (mg/L) Ammonia conversion Maximum historical influent concentration minus permit limit (mg/L) Nitrate removal Assumed to be zero (mg/L) Aeration basin dissolved 1 (mg/L) oxygen Aeration basin 90th percentile (highest) value ('C) temperature Ambient air temperature Highest 1995 daily temperature in month (=F) Solids yield 0.875 lb sludge/lb BOD removed per Tri-Lakes WWTP Blower SCFM Calculated from above Figure 6 compares the projected peak day monthly aeration requirements against the 4,550 SCFM total capacity, and the 3,475 SCFM firm capacity (one 100 hp blower out of service) of the existing blower system. As indicated the four existing blowers do not have enough capacity to provide the air required at the re- rated plant conditions. In order to provide adequate air capacity, the Windsor WWTP will modify or replace the existing blowers, when peak day air requirements reach the firm air capacity of 3,475 SCFM. I I Recertification Study for Tri-Lakes and Windsor WWTP's 29 I • x_ 4 _; U --, O ,.:,,,,,,,,,,,,:".% cn Qeft:. '.. a) : E 2 4) U c) 1011.101illiiiiMiliitiiiiii$ iiiiiii:,.. E a) ::y✓e"H>: ..:F'tsv :"v,"F:7; :AE"..',Y:::;.':k ':`a:�": 'Q:i�'iFyQ:: il if, O Cs p8.inLp.;isrYy!:Mia mik s::Ps.�,�..,:.o,?.,.`. ..� . " tog .:0 5 'SRS i;!'i ii ii:li::!D..:t: ii as9iMi:::M:::if ::: Z L : .r�:3.3.,'�`,`t,:8Y.:3k:.�f:f5?k£;�%U.<.J.� n%.:4»s::ssxs:...,Lsas::.::.r.ss^s:....:..a:.�:4i"r.�'Y.?iiiiyiia. 0kit ` i �..6OW.. a.c`PM.'.9f4s`,2 :. .5, .J u, ,3'i. .i`;.;a t<L,,.A..> .::4`≤ .:£..is. E r 11 $2 a ::':!iPigigiMillittlittiarilliStil."4. tangiiiiMiggiggRoiimmimi:::im)ii::„.. (.0a) .„ = 3-w 0 N � a R� ,�^ . , v 1. kR S L . Y:..:: Rk SdR9K3""�s2t��AoR£ � , >.� � , , •sir.... a • C ICZ l O ��<' txy9o�p`161. 3 ` �s @ sS �3 i t y : sin WC71 F Cr) Yr f?4SL xV .S ., V '. 0 E U P •` ..41CV. CI y?: Q' Q) H CZU - � Q o C .n • • ?4§%:.:SAX•b::1:?..::,:.,.:Re..::::iC:::itcCCCCCC:]*i:Nf:CMCC:iftl::.:Mif,•:::::i:M:•. S--, . E ....... .:._ .:..:. v L .u' wen • • soccs O ca •c g CID it to .....-.).iiiiiiiiik Li) a C 48 2 t‘c N1/4, a) LL Wiiiii................................ „ ........,....................... 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 CD co d• dr c0 co N N I 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Secondary Clarifiers The Tri-Lakes and Windsor WWTP's each have two, identical. fifty-foot-diameter, secondary clarifiers. The clarifiers are center feed with rapid sludge return and bottom scrapper removal to efficiently remove sludge from the clarifier bottom. Side water depth is 12 feet. Table 19 compares the secondary clarifier surface overflow rates, solids loading rates, detention time, effluent weir loadings and side wall water depth with the CDPHE Design Criteria at the re- rated plant capacities. The evaluation assumes that each facility has two clarifiers in service. With two clarifiers in operation, both the Tri-Lakes and Windsor facilities meet all CDPHE and RTW design criteria at the projected flows. Table 19 Secondary Clarifier Evaluation Units CDPHE Tri-Lakes Windsor Criteria Applicable Process Applicable Process Flow, MGD Value Flow, MGD Value Surface overflow rate gal/day/sq. ft. © Average design flow ≤600' 1.76 448 2.3 586 @ Maximum month flow ≤10502 2.8 712 2.8 713 © Peak hour flow ≤1400 5.0 1274 5.0 1.274 Solids loading rate lb/1t2/day @ Maximum month flow 2.8 30 2.8 30 plus RAS ratio = 1.0 Detention time hours @ Average design flow 1-4 1.76 4.8 2.3 3.7 @ Maximum month flow z3.0 2.8 3.0 2.8 3.0 Effluent weir loadings gal/day/ft @ Peak hour flow ≤20,000 5.0 1,440 5.0 1.440 Side water depth feet z10 12 12 1 ' For extended aeration systems, Table H-2, CDPHE Design Criteria, June 1994 2 600 x 1.75 = 1050 gal/day/sq. ft., per footnote 1, Table H-2, CDPHE Design Criteria, June 1994 i I Recertification Study for Tri-Lakes and Windsor WWTP's 30 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Disinfection Tri-Lakes WWTP State disinfection design criteria requires 30 minutes of chlorine contact time at peak hourly flow. Table 20 illustrates the chlorine contact detention times which are projected at Tri-Lakes WWTP at the re-rated capacity of 2.8 MGD. As illustrated, the re-rated plant satisfies the 30 minutes criteria only at annual average flow. However, disinfection system performance experience at Tri- Lakes and other WWTP's indicate that contact time is not the only factor which determines disinfection efficiency. Table 20 Chlorine Contact Basin Detention Times at Tri-Lakes WWTP Flow, MGD Detention Time, minutes Average annual flow, OA 1.76 34 Maximum month average flow, QM 2.8 21 Maximum day flow, Qo 3.58 16.9 Peak hour flow, OH 5 12 The Tri-Lakes disinfection system has demonstrated excellent 1 performance during its three years of operation. Although the facility has fecal coliform limits of 2,345 and 4,690 fecals per 100 ml (monthly and weekly geometric mean values), the highest 1 weekly and monthly geometric mean values reported were 29 and 190, respectively for the three years of Tri-Lakes operation. The highest individual fecal coliform value ever reported was 190 fecal 1 coliform per 100 ml. The design of the chlorine contact chamber which minimizes the opportunity for short circuiting, likely contributes to this high level of performance (Figure 7). An 1 evaluation of the 1992, through 1995, Tri-Lakes' effluent fecal coliform data was done to determine if contact time is the critical control factor for achieving disinfection, or if alternative control parameters might be more or equally valid. Figures 8 through 10 show the fecal coliform data compared to the contact time, chlorine residual and CT (contact time times concentration) used of the Tri-Lakes facility. The contact times I Recertification Study for Tri-Lakes and Windsor WWTP's 31 961188 18" CLARIFIER 2~ CL EFFLUENT _c 2 SOLUTION OPENING o - - 0 15'-0" • OPENING 18" TO DISCHARGE 201-0" 4,---1" SO2 ISOLUTION i 1 1 FIGURE 7 TRI LAKES WWTP CHLORINE CONTACT BASIN Rothberg, Tamburini & Winsor, Inc. 9611SS / 0 • \� $ 0 4 -f :§ } / ) @ oC f d \ o �f ix _@ / z �/ [ A E ) A m . —co \ t / a) CJ \ , » _§ § . , ) \ * 1-, o » * / \ , . m 0 \ / , @ * -g k g ! CO ! T a O '' w ° w cc 2 9 \ 0 0 \ 0 0 ° D , r r g (sa mmGuu2 Topwoo Li_ 1 | 961188 5 0 o 0 - 0.3 - rs - E A 7 - c E� u O W * - awn Q., A .a O O -o - N o -. X O U - Ct aZ bD O X N 31 X _ E `o 0 XXX X - U E - X X Y a\ I X U a X <L I~• M X O IX XXX X 0 U C X4 - a, ( X XX X X - ti I IX !X X X - , 1-. X X X Xy3X XX 0 X X XX X XXXX X - 0 o X X310 WI3C Y X I ME U .14 CCt 771 D- U . I4 XX XXX3II 11:41E XXX - LL H I rn w co 0 0 0 coCO d 0 0 I r0 r - — C, (sa;nuiw) awil pawoo 0 I I 961188 U A O O :..7. -O a - �3 N M a' L W - re -Q _T C C ta W T - Z N N ui L ^` Q W E NA N r tin N N (6 .--+ C\ N 14 c) U N Y N N N F O M 1 ECN _0 cn N N N �a N N ,-'-' N N N - cn NN N NU ti 1 N N N o- N - cg N N N WNm4DM N - O LII 10. N N NUN N N - ;_ O y N DU N=UNI DAWN **I D41 N - U -14 N N N1 DIN D24 MI NW N N N N N N - w 0 T W N IttIk NU N N DM NN0169 N iIN T CC O rn m Co O V C) O O O O O O O OO 1 T c, (1/6w,sa;nuiw) a5 so4 . awil;os;uoo LL 1 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's used in the figues were calculated based on the observed flow at the time of fecal coliform sample collection. As indicated in Figures 8 and 9, there was poor correlation between the contact time and the fecal coliform values reported by the facility. Figure 10 compares the CT value against the fecal coliform level. As expected, as the CT values increased, the number of fecal coliforms in the effluent are reduced. The highest fecal coliform values reported at Tri-Lakes, which represent the "worst case" disinfection, were used to define the line shown in Figure 10. The CT/fecal coliform values plotted on or to the left of the line have produced a final effluent with no more than 190 fecal coliforms per 100 ml. The line is plotted as straight, but as the line approaches a CT of zero, it would be expected to dramatically veer off to the right as CT values become very low. Based on the position of the line, the low fecal coliform values observed, and the considerable difference between the fecal coliform levels thus far observed at Tri-Lakes and the effluent limit, a minimum CT value of 15 appears to provide adequate disinfection assuming an acceptable minimum level of residual chlorine is present. A similar evaluation was done comparing the fecal coliform count as a function of chlorine residual at the end of the chlorine contact basin (Figure 11). Based on this figure, a minimum 0.2 mg/L residual chlorine concentration appears adequate for i disinfection, assuming adequate contact time is provided. Table 21 shows the minimum final residual chlorine concentration (at the end of the chlorine contact basin immediately prior to dechlorination) required to maintain a minimum CT value of 15. As indicated, a chlorine residual value of 0.45 to 1.36 mg/L will be adequate for all flow conditions. I Recertification Study for Tri-Lakes and Windsor WWTP's 32 961188 U 5 0 0 o O 0 o - v W 9 - v1 = N � • O rn CS N A A eat - a E E _• E C4o - v _ c o .. c L V .6: J N d O :a tiro W w r.8 U ■ - 4 0 0 -o - E 0 ■ ■ - 0 ■ o _ z - ■ ■ N I I . - E 'ti o .-� � •y o ■ ■ Ill - U n i I ■ S ■ I C a\ o ... Q\ o _ Q ■ ■ ■ ■ I IN cn ■ I I - ■ ■ ■ ■ ■ ■ - v, H ■ ■ ■ ■ ■ _ ■ ■ f ■ I ■ ■ ■ ik I x ■ ■■ f t ff■ HMI ■■■ - U :d U ■ MUM MOM =f■ ■ f■ ■ ■ ■ ■ - LI-4 H T T I W ■ ■ ■ f ■■ ■ • 1 f■ Of I T CC co NJ- N , co co No D 1 r r r 6 6 6 6 (3 ( (1/6w) tenpisaH auuoty0 LL I 961.1ss • Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Table 21 Chlorine Dosage Required at Projected Flow to Achieve CT*=15 Flow, Contact Required MGD Time, Chlorine minutes Residual, mg/L Average annual flow, QA 1.76 34 0.45 Maximum month average flow, QM 2.8 21 0.71 Maximum day flow, Qo 3.58 16.9 1.13 Peak hour flow, °H 5 12 1.25 Peak instantaneous, Q, 5.5 11 1.36 • CT is residual chlorine concentration at the end of the chlorine contact basin multiplied by contact time (mg/L x minutes) Windsor WWTP The Windsor WWTP has a monthly and weekly fecal coliform limit of 6,000 and 12,000 (geometric mean), respectively. Windsor's ultraviolet (UV) disinfection system was sized to attain an effluent with the geometric mean fecal coliform of 6000/100 ml or less for a peak flow condition of 3.5 MGD. These flows should be considered the maximum system capacity unless plant effluent suspended solids can be guaranteed to a consistently low level or unless effluent fecal coliform limits are relaxed. Therefore, expansion of the ultraviolet disinfection system will be required when peak plant flows exceed 3.5 MGD. The existing UV disinfection channel has a stainless steel baffle which reduces the channel width to three foot where the bank of UV lights is located. Removal of the baffle would allow the UV bank to be expanded by an additional two foot of width which will increase the peak flow capacity of the UV system to approximately 5.8 MGD. This additional UV capacity will be added when peak plant flows reach 3.5 MGD. Recertification Study for Tri-Lakes and Windsor WWTP's 33 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Biosolids Storage Facilities Tri-Lakes WWTP The biosolids storage facilities at the Tri-Lakes WWTP consist of a aerated biosolids storage lagoon and a decant facility which enables the lagoon supernatant to be decanted. A simple, conservative estimate was made of the highest potential biosolids production expected for the Tri-Lakes WWTP at the revised treatment capacity of 2.8 MGD maximum monthly flow. The estimate was made using the following assumptions: • The average annual flow of 1.76 MGD. • The maximum projected influent BOD of 300 mg/L would occur every day. • The solids yield would be 0.875 year round. The 1995 annual average yield factor was 0.72 pounds solids/ pound BOD removed and the maximum monthly value was 0.95. • Waste activated sludge concentration would be 3600 mg/L total solids (the lowest monthly average for 1995 was 3637 mg/L). • Aerobic digestion, settling and decanting of the digestion/storage lagoon will result in an average digested sludge concentration of 2.0% TS. • Only half the storage lagoon volume is available for biosolids storage, the other half is required for successful decanting of supernatant. Based on these assumptions, annual waste activated solids production would be 703 tons per year with a total annual volume of 128,000 gallons (@ 3600 mg/L) and a volume of 23,100 gallons (@ 2% TS) in the biosolids storage lagoon after decanting. Using these figures, the storage lagoon (volume 8.9 million gallons) has 69 days of detention time without decanting and 192 days of detention time when decanting is used. Thus, the storage capacity and detention times of the lagoon are adequate for the re-rated plant capacity. 1 Recertification Study for Tri-Lakes and Windsor WWTP's 34 1 961188 Reassessment of Treatment Capacity for Tri-Lakes and Windsor WWTP's Windsor WWTP The biosolids storage facilities at the Windsor WWTP are very similar to those at Tri-Lakes. The Windsor biosolids storage facilities consist of a aerated biosolids storage lagoon of greater than 8 MG capacity and a decant facility which enables the lagoon supernatant to be decanted. A simple, conservative estimate was made of the highest potential biosolids production expected for the Windsor WWTP at the revised treatment capacity of 2.8 MGD maximum monthly flow. The estimate was made using the following assumptions: • The average annual flow of 2.3 MGD. • Every day would have the maximum projected influent BOD of 278 mg/L. • The solids yield would be 0.875 year round (a conservative, high average yield, figure based on Tri-Lakes WWTP data. See previous section on Tri-Lakes). • Waste activated sludge concentration would be 3000 mg/L total solids (based on an estimated low mixed liquor concentration of 1500 mg/L and minimum concentration factor in the clarifier of 2 to 1). • Aerobic digestion, settling and decanting of the digestion/storage lagoon will result in an average digested sludge concentration of 2.0% TS. • Only half the storage lagoon volume is available for biosolids storage, the other half is required for successful decanting of supernatant. Based on these assumptions, annual waste activated solids production would be 851 tons per year with a total annual volume of 186,500 gallons (@ 3000 mg/L) and a final volume of 28,000 gallons (@ 2% TS) in the biosolids storage lagoon after decanting. Using these figures, the storage lagoon (volume 8.0 million gallons) has 43 days of detention time without decanting and 143 days of detention time when decanting is used. Thus, the storage capacity and detention times of the lagoon are adequate for the re-rated Windsor plant capacity. I Recertification Study for Tri-Lakes and Windsor WWTP's 35 961188 BEFORE THE WELD COUNTY, COLORADO, PLANNING COMMISSION RESOLUTION OF RECOMMENDATION TO THE BOARD OF COUNTY COMMISSIONERS Moved by Ron Sommer that the following resolution be introduced for passage by the Weld County Planning Commission. Be it resolved by the Weld County Planning Commission that the application for: PLANNER: Gloria Dunn NAME: Town of Windsor ADDRESS: 301 Walnut Street, Windsor, CO 80550 REQUEST: Site Application for expansion to an existing wastewater treatment facility LEGAL DESCRIPTION: SE4 SE4 of Section 34, T6N, R67W of the 6th P.M., Weld County, CO LOCATION: East of State Highway 257 & south of the Kodak Colorado Division plant be recommended favorably to the Board of County Commissioners for the following reasons: This request is consistent with the Weld County Comprehensive Plan's Public Facility and Service goals and policies and Urban Growth Boundary Area goals and policies. The proposed improvements to the existing wastewater treatment facility will increase treatment capacity and will not be a duplication of services. The expanded wastewater treatment facility will have the capacity to adequately serve existing users, as well as development which is proposed for the Windsor area. This proposal does not appear to have negative impacts on the general health, safety and welfare of the present and future residents of Weld County. The Weld County Health Department recommends approval of the site application. The North Front Range Water Quality Planning Association will consider this request at its July 18, 1996, meeting. The Weld County Planning Commission's recommendation for approval is conditional upon the following: 1) All new construction associated with expansion of the wastewater treatment facility shall comply wrath Flood Hazard Overlay District requirements, if applicable. Motion seconded by Marie Koolstra. For Passage Against Passage Richard Kimmel Ron Sommer Shirley Camenisch Jack Epple Marie Koolstra Arlan Marrs Ann Garrison The Chairman declared the resolution passed and ordered that a certified copy be forwarded with the file of this case to the Board of County Commissioners for further proceedings. CERTIFICATION OF COPY I, Jill Boshinski, Recording Secretary for the Weld County Planning Commission, do hereby certify that the above and forgoing resolution, is a true copy of the resolution of the Planning Commission of Weld County, Colorado, adopted on July 2, 1996. Dated the 2nd of July, 1996 l+ll Boshinski Secretary 961188 DATE: July 2, 1996 NAME: Town of Windsor ADDRESS: 301 Walnut Street, Windsor, CO 80550 REQUEST: Site Application for expansion to an existing wastewater treatment facility LEGAL DESCRIPTION: SE4 SE4 of Section 34, T6N, R67W of the 6th P.M. , Weld County, CO LOCATION: East of State Highway 257 & south of the Kodak Colorado Division plant THE DEPARTMENT OF PLANNING SERVICES' STAFF RECOMMENDS THAT THIS REQUEST BE APPROVED FOR THE FOLLOWING REASONS: This request is consistent with the Weld County Comprehensive Plan' s Public Facility and Service goals and policies and Urban Growth Boundary Area goals and policies. The proposed improvements to the existing wastewater treatment facility will increase treatment capacity and will not be a duplication of services. The expanded wastewater treatment facility will have the capacity to adequately serve existing users, as well as development which is proposed for the Windsor area. This proposal does not appear to have negative impacts on the general health, safety and welfare of the present and future residents of Weld County. The Weld County Health Department recommends approval of the site application. The North Front Range Water Quality Planning Association will consider this request at its July 18, 1996, meeting. The Department of Planning Services' staff recommendation for approval is conditional upon the following: 1) All new construction associated with expansion of the wastewater treatment facility shall comply with Flood Hazard Overlay District requirements, if applicable. 961188 LAND-USE APPLICATION SUMMARY SHEET Date: June 25, 1996 NAME: Town of Windsor ADDRESS: 301 Walnut Street, Windsor, CO 80550 REQUEST: Site Application for expansion of a wastewater treatment facility LEGAL DESCRIPTION: SE4 SE4 of Section 34, T6N, R67W LOCATION: East of State Highway 257 & south of the Kodak Colorado Division plant POSSIBLE ISSUES SUMMARIZED FROM APPLICATION MATERIALS: The Colorado Department of Health, Water Quality Control Commission's regulations require that the applicant submit the site application to all appropriate local governments, planning agencies and state agencies for review and comment prior to submission to the Colorado Department of Health' s District Engineer. The regulations further state that if the proposed facility is located in the unincorporated area of a county, the county planning agency should be required to comment upon the relationship of the treatment works to the local long-range comprehensive plan for the area as it affects water quality including the location in the flood plain and capacity to serve the planned development. The county agency should also comment upon the relationship of the treatment works to the comprehensive plan for the area as it affects water quality for the proposed treatment works to be located within the boundaries of a city or town. The North Front Range Water Quality Planning Association is currently reviewing the proposal. The Weld County Health Department recommends approval of the proposed improvements. 961188 Rothberg larnburiru Winsor Mr. Todd Hodges May 13, 1996 Weld County Planning Department RO-2892-SC 1400 North 17th Avenue SL# 11257 Greeley, CO 80631 Reference: Windsor WWTP Site Application Dear Mr. Hodges Please find enclosed eleven copies of the Site Application for the Town of Windsor's Wastewater treatment facility. The site application requests that the capacity of the Windsor treatment facility be established at 2.8 MGD. The new rating is based on plant modifications which were completed in October 1995, and on the demonstrated performance of the Tri-Lakes Wastewater treatment facility, a nearly identical plant located near Monument, Colorado. The technical evaluation of the plant capacity is presented in the report entitled, "Reassessment of Treatment Capacity for the Tri-Lakes and Windsor Wastewater Treatment Plants." Eleven copies of this report are also enclosed. Colorado site application procedures require that the Weld County Planning Commission and Board of Commissioners review and sign the site application. It is our understanding that by submitting the site applications at this time, the application will be considered at the July 2, 1996 Planning Commission meeting and at the July 10, 1996, Board of Commissioners meeting. Three, unbound copies of the site application are also enclosed. These unbound copies are the documents which should actually be signed by representatives of the Planning Commission and Board of Commissioners. I will be contacting you before the Planning Commission meeting. Please feel free to call if you have any questions or concerns regarding the site application. Thank you for your time and consideration. Very truly yours, Rothberg, Tamburini & Winsor, Inc. Bill J. Morgan Senior Engineer BJM/img Enclosure Professional Engineers and Consultants 961188 Offices in Denver and Colorado Springs 1600 Stout Street/Suite 1800/Denver, Colorado 80202-3126/(303) 825-5999/FAX (303) 825-0642 Hello