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Biosolids Handling Study - 2010tJ y 7 �11 tit f/a c J ��� "< . ;_ 'rtv^l61 �\ �ti5 .. �.ws�+=r a"�"Mi I5 7 "•✓�� Biosolds Hand ling Study FINAL June 2010 Engineers ...Workin�o� r�+ith,a_te•" June 14, 2010 4836C01 City of Pismo Beach 760 Mattie Road Pismo Beach, CA 93449 Attention: Mr. Dwayne Chisam, Public Works Director Subject: Biosolids Handling Study Dear Mr. Chisam: Based on our recent discussions, Carollo Engineers, P.C. (Carollo) has finalized the Biosolids Handling Study (Study). The purpose of this Study was to determine the best long-term biosolids management approach for the City of Pismo Beach (City). As a result of this Study, two general determinations were made: 1) The existing dissolved air flotation thickener (DAFT) and the belt filter press (BFP) have reached the end of their useful life. 2) A recommendation for replacement of the existing solids handling equipment with a Gravity Belt Thickener (GBT) and a Screw Press were presented. The recommended system includes a thicken ing/dewatering facility consisting of a concrete pad covered by a metal structure and an associated truck scale for accurately weighing the amount of biosolids hauled offsite. The total costs for these recommended facilities are $3.1 million. Should the City desire to complete the construction in phases, Section 3.5 presents a two phased approach. The first phase includes constructing the thicken ing/dewatering facility and installing the GBT only at a cost of $1.9 million dollars. The second phase would include installation of the Screw Press and other ancillary components including demolition and the truck scale at a cost of $1.2 million. The costs are based on the estimates completed in August 2009 when the original draft was completed. Based on information from major equipment vendors, these costs are still valid. It is also estimated that these costs will remain flat through 2011 and then escalate at a rate of approximately 2 percent per year through 2013. One notable change in the final Study is the increased cost for the Screw Press. During our last meeting, the option to reuse biosolids within the County of San Luis Obispo (County) was discussed. Due to the current ordinance, biosolids land applied in the County must meet Class A standards. Investment in a "Class A compatible" Screw Press will give the City the flexibility to meet these standards in the future without the risk of stranded assets. However, this upgraded Screw Press is approximately $90,000 more than the basic Screw Press presented previously. While the cost for this upgraded Screw Press has been included in the cost estimates, the final decision to include it as part of the project can be made during the design process. a 7580 North Ingram Avenue, Suite 112, Fresno, California 93711 P. 559.436.6616 F. 559.436.1191 C:1pw_workinglprojeclwise%warMdms917961Chisam002LH.dac carollo.com Mr. Dwayne Chisam City of Pismo Beach June 14, 2010 Page 2 For the benefit of constructability, the proposed biosolids facilities will be constructed in the vacant paved area just east of the existing DAFT and abandoned digester. This will allow the new facilities to be built while the existing biosolids handling system remains in operation. This approach will result in only minimal interruptions when the new equipment comes online. Once demolished, the DAFT, abandoned digester, generator/boiler building, and BFP building area will be clear and can be utilized by the City. As previously discussed, we recommend that the facilities be designed as one bid package. The bid package could be set up for contractors to provide separate bid items for building either Phase I, Phase II, or both. Designing the system as a whole provides for consistent design criteria and standards. Having a bid package for the entire system would allow the City to bid the entire project and maximize the benefit of favorable bid results in this current low bid atmosphere. The estimated design costs are approximately $300,000 to design the $3.1 million biosolids facilities as presented in Table 3.7. We appreciate the opportunity to assist you in identifying the biosolids project(s) that will best fit both your short-term and long-term needs. If you have any further questions please feel free to call us at 559.436.6616. Sincerely, CAROLLO ENGINEERS, P.C. Amando Garza, P.E. Partner AGG/ETC:cjp EricT. Casares, P.E. C.\pw_workinglpro KtWse%ward�dms917981Chis OD2LH.dw carollo.com 4C5414X� CITY OF PISMO BEACH BIOSOLIDS HANDLING STUDY FINAL June 2010 73351 12/31/10 7580 NORTH INGRAM AVENUE • SUITE 112 • FRESNO, CALIFORNIA 93711 • (559) 436-6616 • FAX (559) 436-1191 pw:/ICamllolDmumenWClienUCAlPismo14836C01/Deliverables/BiosolidsHandlingSludy CITY OF PISMO BEACH BOISOLIDS HANDLING STUDY TABLE OF CONTENTS Paae 1.0 BACKGROUND.........................................................................................................1 1.1 Purpose and Scope......................................................................................... 1 2.0 EXISTING BIOSOLIDS HANDLING FACILITIES...................................................... 1 2.1 Dissolved Air Flotation Thickener (DAFT)........................................................ 3 2.2 Digester No. 2................................................................................................. 5 2.3 Belt Filter Press...............................................................................................6 2.4 Biosolids Disposal...........................................................................................8 3.0 BIOSOLIDS HANDLING PROCESS EVALUATION..................................................8 3.1 Thickening.......................................................................................................8 3.1.1 Gravity Belt Thickener.......................................................................9 3.1.2 Vehicle Scale..................................................................................10 3.1.3 Demolition.......................................................................................10 3.2 Biosolids Dewatering..................................................................................... 11 3.2.1 Alternative No. 1 (Screw Press)......................................................12 3.2.2 Alternative No. 2 (Centrifuge)..........................................................13 3.2.3 Alternative No. 3 (Belt Filter Press Rebuild)....................................17 3.3 Comparison of Mechanical Dewatering Processes ........................................ 21 3.4 Recommended Project..................................................................................24 3.5 Project Phasing.............................................................................................26 3.5.1 Phase I — Thickening......................................................................26 3.5.2 Phase 11— Dewatering.....................................................................27 3.6 Next Steps.................................................................................................... 27 LIST OF TABLES Table 1 Current Wasting Operation................................................................... Table 2 DAFT Operating and Design Criteria .................................................... Table 3 Digester No. 2 Operating and Design Criteria ....................................... Table 4 Belt Filter Press Operating and Design Criteria ..................................... Table 5 Gravity Belt Thickener Design Criteria .................................................. Table 6 Vehicle Scale Design Criteria............................................................... Table 7 Alternative No. 1 (Screw Press) - Preliminary Budgetary Costs ............ Table 8 Alternative No. 2 (Centrifuges) - Preliminary Budgetary Costs .............. Table 9 Alternative No. 3 (BFP Rebuild) - Preliminary Budgetary Costs............ Table 10 Sludge Dewatering Design Criteria Summary ....................................... Table 11 Dewatering Alternatives Net Present Value Cost Comparison .............. Table 12 Biosolids Dewatering Processes — Advantages and Disadvantages ..... Table 13 Phase I —Thickening Preliminary Budgetary Costs ............................... Table 14 Phase II - Dewatering Preliminary Budgetary Costs .............................. FINAL — June 2010 {nv:llCarollolDaumentslClienOCNPismol4836COliDeliverableslBiosolidsHandlingStudy LIST OF FIGURES Figure 1 Existing Biosolids Handling Facilities..............................................................2 Figure 2 Alternative No. 1 Layout................................................................................14 Figure 3 Alternative No. 2 - Layout.............................................................................15 Figure 4 Alternative No. 3 - Layout.............................................................................19 Figure 5 Process Flow Diagram..................................................................................25 FINAL — June 2010 pw:IlCamlldDmumenWClienVCA/Plsmol4836COIlDeliverables/BiosolidsHandlingBiudy City of Pismo Beach BIOSOLIDS HANDLING STUDY filt�Y:IK:Lr13�l�L`l�' 1.1 Purpose and Scope The purpose of this report is to identify upgrades to improve the long-term performance and reliability of the biosolids handling facilities at the City of Pismo Beach (City) Wastewater Treatment Plant (WWTP). An assessment of the City's current biosolids handling practices is crucial at this time for the following reasons: • During the last upgrade of the WWTP in 2003, the biosolids handling facilities were left virtually untouched; • Existing belt filter press (BFP) requires a major rebuild; and • Several other components including the dissolved air flotation thickener (DAFT) have reached the end of their useful life. As part of this report, Carollo Engineers (Carollo) has conducted a site visit to assess the condition of the existing biosolids handling facilities, developed design criteria for improvements to the biosolids thickening and offsite hauling practices, and performed an analysis of several biosolids dewatering alternatives. The study culminates in Carollo's final recommended project that encompasses all the components of a comprehensive biosolids management solution for the City. 2.0 EXISTING BIOSOLIDS HANDLING FACILITIES This section describes the current biosolids handling operation as well as the condition of individual processes and equipment at the Pismo Beach WWTP. The biosolids handling facilities include the following components: C Thickening Y Sludge holding/anaerobic digestion • Dewatering • Offsite disposal The existing biosolids handling facilities are shown in Figure 1. FINAL — June 2010 pe.//Carollo/DmumentsICIienUCAlPismo/4836COI/Deliverables/BiosolidsHandlingStudy I o G W N U CD 0m ;u 0 02 = C90Za- LL?J00 N z zi} 2 2 0 F U) L) O m A iv � IL m � � � C _ �xx/1C O N W = 9 C 0 J e �, Current biosolids production and wasting information is summarized in Table 1. These criteria are used to assess the operation of existing processes as well as develop design criteria for the alternatives analysis process. Table 1 Current Wasting Operation Biosolids Handling Study City of Pismo Beach Criteria Value Waste Flow Rate, gpm 90 Waste Volume, gpd 42,480 Waste Solids Concentration, percent 0.6 Waste Solids, ppd 1,790 Wasting Schedule, days/week 7 Wasting Duration, hr/day 8 Notes: (1) Based on current operating data (May/June 2009). 2.1 Dissolved Air Flotation Thickener (DAFT) Currently, the return activated sludge/waste activated sludge (RASIWAS) Pump Station pumps WAS from the secondary clarifiers to the DAFT. The DAFT was originally constructed in 1983, and is used to thicken sludge upstream of Digester No. 2 and increase sludge storage capacity in the digester. The existing DAFT and associated equipment are shown in Photo 1. Two 3 horsepower (HP) Monoflo pumps send sludge from the DAFT to Digester No. 2. Supernatant from the thickening process flows by gravity to the BFP Sump Pump Station and is pumped to the headworks. The operating and design criteria for the DAFT are summarized in Table 2. FINAL — June 2010 3 pw://Carollo/Documents/ClienUCNPismol4636C01/Deliverables/BiosolidsHandlingSludy Table 2 DAFT Operating and Design Criteria Biosolids Handling Study City of Pismo Beach Criteria Value Diameter, ft 20 Surface Area, sq ft 314 Hydraulic Loading, gpm(�) 90 Solids Loading, Ibs/hr/sq ft 0.8 Solids Capture, percent 85 Thickened Sludge Volume, gpd 4,740 Thickened Sludge Concentration, percent 3.8 Thickened Sludge, ppo(3) 1,520 Thickening Schedule, days/wk 7 Thickening Duration, hr/day 8 Notes: (1) Based on current operating date (May/June 2009). (2) Hydraulic: loading design criteria of 120 pgm at 5.0 percent solids. (3) Assumed solids capture rate of 85 percent. The existing DAFT is the major bottleneck in the current solids handling operation at the WWTP. City staff must waste on a daily basis for the duration of a full shift in order to stay within the 120 gallons per minute (gpm) capacity of the existing unit and maintain the desired solids retention time (SRT) in the oxidation ditches. The DAFT is also more than twenty-five years old and has reached the end of its useful life. For these reasons, Carollo FINAL — June 2010 4 pw:llCamilNDocuments/ClienUCNPismo/4836COliDeliverablesA3iosolidsHandlingStudy recommends the DAFT and thickened sludge pumps be replaced with a new mechanical dewatering system. The new thickening system will be further discussed in Section 3.1 of this report. 2.2 Digester No. 2 Digester No. 2 was originally constructed as a conventional anaerobic digester in 1995 complete with a heating and pump -mix system. Digester No. 2 and the BFP feed pumps are shown in Photo 2. As part of the last upgrade to the WWTP, Digester No. 2 was converted to a sludge -holding tank ahead of the dewatering process. Thickened WAS in the holding tank is no longer heated, but a small amount of gas is produced that must be flared. The thickened sludge is fed to the BFP via two 5 HP Shanley pumps. The operating and design criteria for Digester No. 2 are shown in Table 3. Based on the size and age of Digester No. 2, Carollo recommends the digester remain in service in its current capacity as a sludge -holding tank. However, based on conversations with WWTP staff, the existing heating equipment is in good condition and the digester could be operated as a functional anaerobic digester at anytime in the future. Based on a preliminary review by Carollo, the City could produce Class B biosolids in accordance with Code of Federal Regulations Title 40, Part 503 (40 CFR 503) by using the anaerobic digester. Several benefits of operating the digester in this mode of operation include: • Volatile solids destruction resulting in less dewatered solids production and reduced hauling costs; • Production of a Class B biosolids product resulting in reduced hauling fees charged by the contract hauler or land applier; and FINAL —June 2010 pw://Carollo/DwumenWClienOCNPismol4836C01Neliwmbles/BimiidsHandlingSWdy • Improved solids dewatering characteristics resulting in higher solids concentrations and reduced hauling costs. While operation of the digester could potentially reduce the City's cost for biosolids disposal, it also presents several drawbacks including: • Additional man-hours required to operate and maintain digester and ancillary heating and mixing equipment; • Additional sampling, testing, and reporting requirements for Class B biosolids certification; Y Potential operational issues (e.g. foaming) resulting from the digestion of extended aeration WAS; and C Potential addition of natural gas to augment digester gas for operating boilers (sludge heating). The impacts of anaerobic digestion on the operation and maintenance (O&M) costs associated with the City's biosolids handling practices will be quantified in a latter section of this study. This analysis will allow the City to determine how the digester will be operated in the future. While the existing Shanley pumps are in good working condition, they may need to be replaced to match the capacity of the new dewatering equipment if the existing BFP is abandoned. Table 3 Digester No. 2 Operating and Design Criteria Biosolids Handling Study City of Pismo Beach Criteria Value Diameter, ft 47 Volume, gal 307,000 Thickened Sludge Feed, gpd 4,740 Detention Time, days 64 Notes: (1) Based on current operating data (May/June 2009). 2.3 Belt Filter Press Solids are currently dewatered at the WWTP with a BFP. The BFP is shown in Photo 3. The BFP is located in an enclosed wooden structure, and was originally installed in 1983. Dewatered solids are discharged from the BFP and conveyed to a sludge storage bin located adjacent to the BFP building. Beltrate from the dewatering process flows by gravity FINAL — June 2010 pw:llCarolldDmuments/ClienYCNPismo/4838C011DelivembleslBiosolidsHandling5tudy to the BFP Sump Pump Station and is pumped to the headworks. The operating and design criteria for the BFP are summarized in Table 4. I r a s ,�-_ ���-dam �.¢ _�`--- -{ ,►' � Table 4 Belt Filter Press Operating and Design Criteria Biosolids Handling Study City of Pismo Beach Criteria Value Size, meters 1.0 Hydraulic Loading, gpm/meter(2) 14 Solids Loading, Ibs/hr/meter 80 Solids Capture Rate, percent 90 Average Solids Concentration, percent 19 Wet Cake Production, tons/day 5.0 Dewatering Schedule, days/wk 5 Dewatering Duration, hr/day 8 Notes: (1) Based on current operating date (May/June 2009). (2) Hydraulic: loading design criteria of 43 gpm/meter at 3.5 percent solids. The existing BFP is more than twenty-five years old and is nearing the end of its useful life. Carollo recommends the existing BFP be rebuilt or replaced with another dewatering technology. Several alternatives for biosolids dewatering at the WWTP are discussed in Section 3.2 of this report. FINAL — June 2010 pw://Carollc/Doament4Client/CNPismo/4836C01/Deliverables/BiosolidsHandling$tudy 2.4 Biosolids Disposal Dewatered biosolids are discharged from the BFP and conveyed to a bin owned by the City. The City currently owns four bins that are moved under the discharge conveyor with a front-end loader. The bins and front-end loader are shown in Photo 4. Each bin has a volume of approximately 30 cubic yards and is loaded with approximately five tons of dewatered cake. Bins are hauled from the site on a weekly basis by San Joaquin Composting for further treatment and land application. 3.0 BIOSOLIDS HANDLING PROCESS EVALUATION Three alternatives are considered for upgrade of the biosolids handling facilities at the Pismo Beach WWTP. The first alternative includes replacement of the existing BFP with a screw press (Alternative No. 1). The second alternative includes replacement of the BFP with centrifuges (Alternative No. 2). The third is based on rebuilding the City's existing BFP and relocating it to a new thickening/dewatering facility (Alternative No. 3). Modifications to other facilities, which are common to all alternatives, will also be discussed in this section of the report and include sludge thickening, a vehicle scale, and demolition. 3.1 Thickening The purpose of sludge thickening at the Pismo Beach WWTP is to increase the solids concentration of the WAS stream prior to sludge holding, thereby reducing the required digester volume for adequate storage capacity. Based on the evaluation of the existing biosolids thickening process presented in Section 2.1, Carollo recommends the existing DAFT and other ancillary facilities be replaced. FINAL — June 2010 8 pw://CarollolDmuments/ClienVCNPismo/4836C01/Deliverables/BiosolidsHandlingStudy Gravity belt thickeners (GBTs) are the most common method of mechanical WAS thickening currently practiced, and the recommended sludge thickening process for upgrade of the Pismo Beach WWTP. The solids concentration of thickened sludge from the GBT is assumed to be approximately 4 to 5 percent. The existing DAFT is currently producing thickened sludge with a solids concentration of approximately 3.8 percent. 3.1.1 Gravity Belt Thickener GBTs have been widely used at municipal wastewater treatment plants for WAS thickening. The GBT is essentially the first stage or "gravity table' of the BFP, which City staff has been using for sludge dewatering for the last twenty-five years. The sludge is introduced to the dewatering zone from a flocculation/distribution tank. The design criteria for sizing of GBTs are based on hydraulic loading rates. A hydraulic loading rate of 250 gpm per meter of belt width is appropriate for design. GBTs are available in sizes of one meter, two meters, and three meters. A summary of gravity belt thickener design criteria is presented below in Table 5. Table 5 Gravity Belt Thickener Design Criteria Biosolids Handling Study City of Pismo Beach Criteria Value Sludge Feed Flow Rate, gpd 59,460 Sludge Feed Solids Concentration, percent 0.6 Thickened Sludge Concentration, percent 4.0 Number of Units 1 Size, meters 1.0 Hydraulic Loading, gpm/meter 150 Solids Loading, Ibs/hr/meter 360 Solids Capture Rate, percent 95 Polymer Feed Rate, Ibs/dry ton 10 Operating Schedule, days/week 5 Operating Duration, hours/day 7 Notes: (1) Based on current operating date (May/June 2009). Based on the assumed operating duration and frequency in Table 5, the use of a single 1-m GBT will have more than adequate capacity to handle the sludge produced at the Pismo Beach WWTP. FINAL — June 2010 pv://CarollolDocumentslClium/CNPismo14836C61Neliverablesl8iosolidsHandlingStudy 3.1.2 Vehicle Scale In order to maximize the amount of biosolids that can be legally loaded to the bins and minimize disposal costs for the City, the City wishes to install a vehicle scale as part of the biosolids handling facility upgrades. Based on direction from City staff, the scale does not need to provide certified weight results. Vehicle scales come in two basic types: Pit type Low -profile While pit type scales offer several advantages to low -profile scales including ease of access to the load cells and other components beneath the scale, pit type scales are generally more expensive and require a means for dealing with the accumulation of water or other material in the pit. Since the scale will be installed in an area where biosolids and wash water could become a problem for the pit, Carollo recommends a low -profile scale be installed at the Pismo Beach WWTP. The scale will be provided with a digital weight indicator located near the vehicle scale and thickening/dewatering facility. The design criteria for the scale are summarized in Table 6. Table 6 Vehicle Scale Design Criteria Biosolids Handling Study City of Pismo Beach Criteria Value Storage Bin Weight (empty), Ibs 4,500 Storage Bid Capacity, Ibsl'I 20,000 Platform Length, ft(2) 35 Platform Width, ft 11 Notes: (1) City staff loads approximately 5 wet tons of dewatered cake to each bin. (2) Based on current loading practices, the scale platform must be twice as long as the hazardous material bin. 3.1.3 Demolition Based on discussions with City staff, Carollo agrees the new thickening/dewatering facility should be located in the area west of Digester No. 2. While the new facilities will be located to the southwest of the existing biosolids handling equipment, Carollo recommends demolition of the DAFT, Digester No. 1, and the Generator/Boiler Building. Digester No. 1 and the Generator/Boiler Building are shown in Photo 5 and Photo 6. The cost for demolition of these facilities has been added to each alternative for upgrade of the biosolids handling facilities at the Pismo Beach WWTP. FINAL — June 2010 10 pva/CarollolDocuments/ClienUCA/Pismol4836CO110olivemblesiBiwolidsHandlingStudy T� I jl i; y f _ya 1) l-' 7 3.2 Biosolids Dewatering The purpose of biosolids dewatering is to increase solids concentration and reduce the weight of dewatered biosolids that must be hauled from the site. The City currently dewaters biosolids mechanically with a BFP. The BFP is approximately twenty years old, and is in need of an extensive rebuild. As an alternative to rebuilding the existing BFP, the City has asked Carollo to evaluate several other mechanical dewatering technologies as part of this report. These technologies include screw presses and centrifuges. FINAL — June 2010 11 pw://Camllo/Daouments/Client/CNPIsmo/4836C01IDeliverables/BiosolidsHandlingStudy 3.2.1 Alternative No. 1 (Screw Press) Alternative No. 1 includes biosolids dewatering with a screw press. The components of Alternative No. 1 include: • Screw press • Thickening/dewatering facility • Thickened sludge pumps • Polymer feed units A layout of Alternative No. 1 is shown in Figure 2. Screw presses have recently received attention in the municipal wastewater field as a viable biosolids dewatering technology, and represent a cost-effective option compared to other conventional technologies. Local wastewater authorities including the Monterey Regional Water Pollution Control Agency (RWPCA) and Cambria Community Services District (CSD) have recently installed screw press units to dewater municipal sludge. The screw press operating at the Cambria Water Quality Control Plant (WQCP) is shown in Photo 7. In a screw press, a screw conveyor moves the biosolids in a reduced diameter screen horizontal bowl. This reduction in diameter results in increased pressure along the length of the screw press, which results in the dewatering of the biosolids to a solids concentration comparable to a centrifuge or BFP. Their solids capture is typically 90 percent. A main advantage of the screw press is its simplicity, which allows it to be operated on a 24-hour schedule, virtually unattended. Another potential benefit of the screw press technology is its ability to produce Class A biosolids. A major screw press manufacturer, Fukoku Kogyo Company, Ltd. (FKC) provides a screw press unit, which couples dewatering and pasteurization utilizing both heat and lime addition to produce biosolids with a solids concentration between 30 and 50 percent. While the City has not currently confirmed a use for Class A biosolids within the County of San Luis Obispo (County), Carollo recommends that if the City chooses to install a screw press at the WWTP, it is "Class A compatible." This requirement translates to sole source of FKC for the screw press equipment, and specific manufacturing requirements for the screw press including American National Standards Institute (ANSI) pressure rating for the screw and insulation of the screw press housing. Typically, a "Class A compatible" screw press has a 40 percent higher equipment cost than a simple dewatering FKC screw press. The cost for the Class A compatible screw press has been included as part of this alternatives analysis. FINAL — June 2010 12 rAv://CarollaDocumenls/Cl,enVCNPismo/4636C01/Deliverables/BiosolidsHandlingSludy A summary of the total project cost for Alternative No. 1 is shown in Table 7. 3.2.2 Alternative No. 2 (Centrifuge) Alternative No. 2 includes biosolids dewatering with centrifuges. The components of Alternative No. 2 include: • Centrifuges • Thickening/dewatering facility • Thickened sludge pumps • Polymer feed units A layout of Alternative No. 2 is shown in Figure 3. Sludge dewatering using a centrifuge employs centrifugal force to achieve the separation, sedimentation, and compression of sludge solids desired. The sludge is separated based on density difference between the solid and liquid phases into dewatered cake and clarified centrate. Of the three basic types of centrifuges (disk nozzle, imperforate basket, and solid bowl), the solid bowl centrifuge is the preferred type for municipal sludge dewatering applications. As sludge is pumped into the solid bowl centrifuge, the sludge solids separate, thicken, and the dewatered sludge is removed along the outside wall of the rotating bowl while the centrate is discharged from the fluid surface near the bowl's center. FINAL — June 2010 13 pw:l/Camllo,'DoeumenWCIIenVCNPismo/4838COIlDeliverableslBiosolidsHandling5tudy D_ V 7 U Q NQ U` w Nc J ZCO 70 KZWc, C7 Uj ZL ELH N LL a to 0} 0 - z 0-Li J a 0 U a m �rAga 6 1! N c OLL LL �a a O Z 2 W 2 goo n N K / • �, st Yam\ "Ve Table 7 Alternative No. 1 (Screw Press) - Preliminary Budgetary Costs Biosolids Handling Study City of Pismo Beach Criteria Value(l) Thickening/Dewatering Facility $558,000 Gravity Belt Thickener $272,000 Polymer Feed Unit $19,000 Thickened Sludge Pumps $72,000 Screw Press Feed Pumps $32,000 Screw Press $360,000 Polymer Feed Unit $15,000 Truck Scale $38,000 Demolition Digester No. 1 $96,000 DAFT $40,000 Generator/Boiler Room $15,000 Yard Piping/Sitework $95,000 Electrical and Instrumentation $285,000 Subtotal $1,897,000 Unidentified Item Contingency (20 percent) $380,000 Subtotal Construction Cost 2009(2) $2,277,000 Engineering, Administrative, and Legal Costs (35 percent) $797,000 Total Project Cost 2009 $3,074,000 Notes: (1) ENR (20 cities) August 2009 = 8564. (2) Includes contractor overhead and profit. Dewatering centrifuges can normally achieve a 15 to 30 percent cake solids concentration with a 90 to 95 percent solids capture. However, the efficiency of dewatering is very sensitive to sludge characteristics, sludge conditioning, and sludge feed rate. A main advantage of centrifuges is their ability to generate high solids concentrations while occupying a relatively small footprint. At the same time, they contain odors well and generate a rather small stream of air to be potentially scrubbed. They also tend to generate clear centrate streams with solids captures exceeding 95 percent. However, higher capture rates are achieved at the expense of relatively high polymer dose. Due to their high rotational speed, centrifuges generate noise, which in many cases results in their enclosure FINAL — June 2010 16 pw:IlCamiloiDowmenWClienUCNPismo/4836COIlDelivemblesiSiosolidsHandlingStudy in buildings. They also have higher energy requirements compared to BFPs and screw presses, and have relatively higher maintenance requirements. However, centrifuges are generally easier to automate compared to BFPs. A summary of the total project cost for Alternative No. 2 is shown in Table 8. Table 8 Alternative No. 2 (Centrifuges) - Preliminary Budgetary Costs Biosolids Handling Study City of Pismo Beach Criteria Value(') Thickening/Dewatering Facility $604,000 Gravity Belt Thickener $272,000 Polymer Feed Unit $19,000 Thickened Sludge Pumps $72,000 Centrifuge Feed Pumps $32,000 Centrifuges $436,000 Polymer Feed Unit $30,000 Truck Scale $38,000 Demolition Digester No. 1 $96,000 DAFT $48,000 Generator/Boiler Room $18,000 Yard Piping/Sitework $105,000 Electrical and Instrumentation $313,000 Subtotal $2,083,000 Unidentified Item Contingency (20 percent) $417,000 Subtotal Construction Cost 2009(2) $2,500,000 Engineering, Administrative, and Legal Costs (35 percent) $875,000 Total Project Cost 2009 $3,375,000 Notes: (1) ENR (20 cities) August 2009 = 8564. (2) Includes contractor overhead and profit. 3.2.3 Alternative No. 3 (Belt Filter Press Rebuild) Alternative No. 3 includes biosolids dewatering with the existing BFP. The components of Alternative No. 3 include: Y Rebuild of the existing BFP FINAL — June 2010 17 pw:/ICamllolDocumenWCllenVCNPlsmol4836C01IDeliverables/BiosolidsHandlingStudy Thickening/dewatering facility Thickened sludge pumps Polymer feed units A layout of Alternative No. 3 is shown in Figure 4. Belt filter presses have been widely used in the United States to dewater sludge from municipal wastewater treatment plants. The BFP at the Pismo Beach W WTP was installed approximately twenty-five years ago, and produces a dewatered cake with approximately 19 percent solids. Based on the age and condition of the existing BFP, Carollo recommends the BFP be rebuilt. The City was previously in negotiations with the manufacturer of the existing BFP, Ashbrook Simon -Hartley® (Ashbrook), regarding a major rebuild of the unit. Rebuilding the BFP would include shipping the existing unit to Ashbrook's factory in Houston, Texas, procurement of an interim dewatering system, and start-up of the rebuilt unit. The rebuild process would take approximately 90 days. An additional component of the rebuild program is replacement of the existing control panel with an upgraded panel that would allow for automatic control of the BFP through the WWTP's existing supervisory control and data acquisition (SCADA) system. A summary of the total project cost for Alternative No. 3 is shown in Table 9. Table 10 presents the design criteria for BFP, centrifuge, and screw press dewatering. For the BFP option, the existing rebuilt unit without a standby is recommended for operation during a single shift, five days per week. Due to City staff's level of comfort with this technology, a standby unit has not been included. For the centrifuge option, one unit in service with one standby is recommended for operation of a single shift, five days a week. Due to the high rotational speed of the centrifuge and their higher propensity for maintenance, Carollo recommends installation of a standby unit. For the screw press option, a single in service unit with no standby is recommended for continual operation, four days per week. FINAL — June 2010 18 pw:IlCarollo'Documents/ClienVCNPismol4836COilDeliverables/BiosolidsHandling$tudy } O S OW`Oj NQ MCOF-:'J W a O w O Z O It LU W N} Z U) >WgQU) LL Q IL a) W W N O J LL O U Q an a N d � m E N Rom' V r� O y LL Rl LL c mC N N Z S W S } Table 9 Alternative No. 3 (BFP Rebuild) - Preliminary Budgetary Costs Biosolids Handling Study City of Pismo Beach Criteria Value(l) Thickening Facility $750,000 Gravity Belt Thickener $272,000 Polymer Feed Unit $19,000 Thickened Sludge Pumps $72,000 Truck Scale $38,000 Demolition DAF $48,000 Digester No. 1 $96,000 Generator/Boiler Room $18,000 Polymer Feed Unit (Belt Filter Press) $15,000 Yard Piping/Sitework $83,000 Electrical and Instrumentation $249,000 Subtotal $1,660,000 Unidentified Item Contingency (20 percent) $332,000 Subtotal Construction Cost 200912> $1,992,000 Engineering, Administrative, and Legal Costs (35 percent) $698,000 Belt Filter Press Rebuild(') $275,000 Total Project Cost 2009 $2,965,000 Notes: (1) ENR (20 cities) August 2009 = 8564. (2) Includes contractor overhead and profit. (3) Includes cost for 90-day rental of an interim belt press dewatering system. FINAL — June 2010 20 pw:llCamlloiDocumentslClienVCNPismo14836COilDelivembles/BiosolidsHandlingStudy Table 10 Sludge Dewatering Design Criteria Summary Biosolids Handling Study City of Pismo Beach Criteria Value(') Thickened Sludge Flow Rate, gpd 7,120 Thickened Sludge Solids Concentration, percent 4.0 Belt Filter Press (Existing) Number of Units (1.0 meter) 1 Number of Units in Service 1 Hydraulic Loading Rate, gpm/unit 20 Solids Loading Rate, Ibs/hr/unit 340 Operating Schedules days/wk 5 Operating Duration, hr/day 7 Centrifuge Number of Units 2 Number of Units in Service 1 Hydraulic Loading Rate, gpm/unit 20 Solids Loading Rate, Ibs/hr/unit 340 Operating Schedules days/wk 5 Operating Duration, hr/day 7 Screw Press Number of Units 1 Number of Units in Service 1 Hydraulic Loading Rate, gpm/unit 10 Solids Loading Rate, Ibs/hr/unit 130 Operating Schedules days/wk 4 Operating Duration, hr/day 24 3.3 Comparison of Mechanical Dewatering Processes Several analyses were performed that considered both the economic and non -economic factors of implementing one of the three mechanical dewatering alternatives for the Pismo FINAL — June 2010 21 pw://CarollolDmumenls/Clien6CNPismo/4836COI/DeliverableslBiosolidsHandlingSfudy Beach WWTP. In addition to the three mechanical dewatering alternatives presented previously, Carollo has also developed a fourth option, which includes mechanical dewatering with a screw press and operation of the anaerobic digester. For the purpose of this study, this option is referred to as Alternative 1A. Carollo has made the following assumptions in order to develop the costs for Alternative 1A including: • No additional capital cost has been added to make the anaerobic digester operational due to the condition of the existing heating equipment; • Anaerobic digester performance is assumed to be 38 percent volatile solids reduction to meet Class B vector attraction reduction requirements; • Cost for sludge hauling per ton will be approximately 10 percent less for digested (Class B) biosolids; Y No supplemental natural gas will be required for sludge heating; • An additional half-time operator will be required to operate and maintain the anaerobic digester; • Screw press will achieve 20 percent solids with the digested sludge versus the 18 percent assumed for undigested WAS. In order to facilitate the alternatives analysis for the four options that have been developed, the project, annual O&M, and 20-year net present value (NPV) costs were first considered. A summary of these cost components is shown in Table 11. Table 11 Dewatering Alternatives Net Present Value Cost Comparison Biosolids Handling Study City of Pismo Beach Alternative Alternative No.1A No. 1 (Screw Press/ Alternative Alternative (Screw Anaerobic No.2 No.3 Option Press) Digestion) (Centrifuge) (BFP) Project Cost $ Thickening/Dewatering Facility $904,000 904,000$ $978,000 $1,215,000 Gravity Belt Thickener $588,000 $588,000 $588,000 $588,000 Dewatering Equipment $659,000 $659,000 $807,000 $299,000 Truck Scale $62,000 $62,000 $62,000 $62,000 Demolition $245,000 $245,000 $245,000 $245,000 ElectricalNard Piping $616,000 $616,000 $695,000 $556,000 Total $3,074,000 $3,074,000 $3,375,000 $2,965,000 FINAL — June 2010 22 pw://CarollolDmumenlsrClienVCNPismo/4636C01/Delivembles/BiosolidsHandlingStudy Table 11 Dewatering Alternatives Net Present Value Cost Comparison Biosolids Handling Study City of Pismo Beach Alternative Alternative No. 1A No. 1 (Screw Press/ Alternative Alternative (Screw Anaerobic No.2 No.3 Option Press) Digestion) (Centrifuge) (BFP) Operation & Maintenance Cost. 1/ME Chemical(2) $25,000 $21,000 $30,000 $19,000 Electricity (3) $5,000 $5,000 $9,000 $3,000 Labor(') $40,000 $80,000 $80,000 $80,000 Maintenance $18,000 $18,000 $21,000 $20,000 Sludge Disposal(5) $84,000 $45,000 $84,000 $84,000 Total $172,000 $169,000 $224,000 $206,000 20-Year Net Present Value. $ Project Cost, $ $3,074,000 $3,074,000 $3,375,000 $2,965,000 Operation & Maintenance(6) $2,660,000 $2,618,000 $3,466,000 $3,289,000 Total Net Present Value Cost $5,734,000 $5,692,000 $6,841,000 $6,254,000 Notes: 1. Based on first year of operation in 2009. 2. Based on an assumed polymer cost of $2.70/pound. 3. Based on a power cost of $0.14/kWh (2008). 4. Based on an assumed labor rate of $40/hour. 5. Based on an assumed sludge disposal cost of $49.00/ton and $45.00/ton for Alternative No. 1A (Class B). 6. Calculated with an inflation rate of 3.0 percent and a discounted rate of 6.0 percent. While Alternative No. 1 (Screw Press) and Alternative No. 1A (Screw Press/Anaerobic Digestion) have essentially the same project cost as Alternative No. 3 (BFP), Alternative No. 1 and Alternative No. 1A have the lowest NPV costs of the alternatives considered. In addition to project and NPV costs, Carollo has also prepared a comparison of the non- economic factors associated with each option. Table 12 presents a qualitative analysis of the mechanical dewatering options considered for the Pismo Beach WWTP. FINAL — June 2010 23 px://CamllolDxumenls[ClionACNPismo/4836C81/Deliverables/BiosolidsHandlingSWdy Table 12 Biosolids Dewatering Processes — Advantages and Disadvantages Biosolids Handling Study City of Pismo Beach Alternative No. 1 A Alternative (Screw Press/ Alternative Alternative No.1 Anaerobic No.2 No.3 Process/Criteria (Screw Press) Digestion) (Centrifuge) (BFP) Energy Requirement + + + Operation & Maintenance Cost + + Noise + + Odor/Corrosion Containment + + + Footprint + Polymer Usage + + + Shutdown/Start-Up Ease + + + Familiarity to City Staff + Ease of Operations + + 3.4 Recommended Project Alternative No.1 (Screw Press) is recommended for upgrade of the biosolids handling facilities at the Pismo Beach WWTP. Overall, Alternative No. 1, along with Alternative No. 1A, were determined to have the lowest NPV cost of any of the alternatives. In addition to NPV cost, these alternatives also have a comparable project cost to the Alternative No. 3. The total project cost for Alternative No. 1 is $3,074,000. With the design of Alternative No. 1, the thickening/dewatering facility will be located in the area southwest of Digester No. 1 and the Generator/Boiler Building. The existing DAFT and BFP will remain in service until construction of the thickening/dewatering facility is complete and the screw press and GBT are in operation. The DAFT unit can then be demolished and the BFP and any ancillary equipment can be removed from the BFP building. After the new biosolids thickening and dewatering equipment are in operation, WAS will be pumped from the secondary clarifiers to the thickening/dewatering facility. Here, WAS will be thickened to a solids concentration of approximately four percent before being pumped to Digester No. 2, which will continue to operate as a sludge holding tank. The thickened sludge pumps will be located in the thickening/dewatering facility. New screw press feed pumps will be installed near Digester No. 2 to pump thickened sludge back to the thickening/dewatering building where a screw press will dewater biosolids and discharge them to one of the City's existing biosolids storage containers. A vehicle scale will be installed under the conveyor discharge point to record the weight of solids deposited in each container. A process flow diagram for the recommended project is shown in Figure 5. FINAL — June 2010 24 pw:llCarolloiDocumenk/ClienUCNPismol4836C011Deliverablesl6iosolidsHandlingSludy h20 � .� w �o m � 00ac�w R omr3zm " V 4 � p a w u I V fo z 7 _ LL W 0 0 LL 2 WZ0 0U0� W 2 US �LLm Ir N O m Z E N C N m ra N _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I 1 I 1 19aE Iu � I sma IF Im 1 a 1 a la 3 I v Irn I m� «x IY S u u rvr Ir I I I c 0 N o Q N O O O w o E m a N vZ f mZ i� a c 02 0 p rn N U U a.0 ELL 0 U 3.5 Project Phasing While Carollo recommends the above components be implemented as a single comprehensive project, we recognize it may be beneficial for the City to take a phased approach to these biosolids handling improvements. A description of this phased project approach is presented below. 3.5.1 Phase I — Thickening While the existing condition of the BFP initially triggered preparation of this study, the DAFT is more than twenty-five years old and also needs to be replaced. City staff also identified the DAFT as the major bottleneck in the sludge wasting and thickening process. For these reasons, the main focus of the Phase I project is replacement of the existing DAFT with a new GBT. Table 13 summarizes the costs for the Phase I project. While the estimated construction cost for the Phase I project is $1,868,000, Carollo estimates the costs may be substantially lower as a result of today's bidding climate. Table 13 Phase 1— Thickening Preliminary Budgetary Costs Biosolids Handling Study City of Pismo Beach Criteria Value(l) Thickening/Dewatering Facility $558,000 Gravity Belt Thickener $272,000 Polymer Feed Unit $19,000 Thickened Sludge Pumps $72,000 Yard Piping/Sitework $58,000 Electrical and Instrumentation $173,000 Subtotal $1,152,000 Unidentified Item Contingency (20 percent) $231,000 Subtotal Construction Cost 200912i $1,383,000 Engineering, Administrative, and Legal Costs (35 percent) $485,000 Total Project Cost 2009 $1,868,000 Notes: 1. ENR (20 cities) August 2009 = 8564. 2. Includes Contractor overhead and profit. FINAL — June 2010 26 pv://Carollo�Dmuments[ClienUCA/Pisma/4836COilDelivemblesiBimolidsHandlingStudy 3.5.2 Phase II — Dewatering As mentioned previously, the BFP is also in need of replacement. However, City staff has had great success in recent years keeping the BFP in service. For this reason, Carollo recommends shifting replacement of the BFP into the second phase of the project. Therefore, the major component of the Phase II project is installation of a new screw press to replace the existing BFP. Also included in the second phase of the project would be demolition of abandoned facilities including the DAFT, Digester No. 1, and Generator/Boiler Building and installation of a new truck scale. The costs for the Phase II project are summarized in Table 14. Table 14 Phase II - Dewatering Preliminary Budgetary Costs Biosolids Handling Study City of Pismo Beach Criteria Value(l) Screw Press Feed Pumps $32,000 Screw Press $360,000 Polymer Feed Unit $15,000 Truck Scale $38,000 Demolition Digester No. 1 $96,000 DAFT $40,000 Generator/Boiler Room $15,000 Yard Piping/Sitework $38,000 Electrical and Instrumentation $113,000 Subtotal $747,000 Unidentified Item Contingency (20 percent) $150,000 Subtotal Construction Cost 2009(2) $897,000 Engineering, Administrative, and Legal Costs (35 percent) $314,000 Total Project Cost 2009 $1,211,000 Notes: 1. ENR (20 cities) August 2009 = 8564. 2. Includes contractor overhead and profit. 3.6 Next Steps Carollo recommends beginning design of both the Phase I and Phase II projects as a single set of plans and specifications. The decision to keep the work as a single project or to split it into two separate projects, as described above, can be made by the City at this time or during the design phase prior to bidding. As described, the Phase I project could also be FINAL — June 2010 27 pw:llCarolloDocuments/ClienVCNPismol4836COilDelivembleslBiosolidsHandling5tudy presented as the base bid with the components of Phase II included as alternative bid items. FINAL — June 2010 28 pw://CarollolDmumenls/ClienUCNPismol4636C011Delivembles/BiosolidsHandlingStudy