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06/08/1983 Agreement
POST, BUCKLEY, SCHUH & JERNIGAN, INC. MONROE COUNTY SLUDGE MANAGEMENT STUDY JUNE 1983 MONROE COUNTY SLUDGE MANAGEMENT STUDY JUNE 1983 Prepared for BOARD OF COUNTY COMMISSIONERS MONROE COUNTY, FLORIDA Prepared by POST, BUCKLEY, SCHUH & JERNIGAN, INC. Consulting Engineers and Planners 889 North Orange Avenue 513 Whitehead Street 10 Palms Plaza Orlando, Florida 32801 Key West, Florida Homestead, Florida 33030 401-503.00 P B Post, Buckley, Schuh & Jernigan, Inc. s T J CONSULTING ENGINEERS and PLANNERS 889 NORTH ORANGE AVENUE, ORLANDO, FLORIDA 32801-1088 • 305/423-7275 • TELEX 808435 June 8, 1983 Charles Aguero, Manager Monroe County Municipal Service District Wing II-B Public Service Building Stock Island Key West, Florida 33040 Dear Mr. Aguero: Re: Monroe County Sludge Management Study Post, Buckley, Schuh & Jernigan, Inc. is pleased to submit this Sludge Manage- ment Study, which discusses alternatives to Monroe County's current sludge disposal operation. A thorough investigation of the County's current and projected quantity and types of sludge generated, along with a review of current available technology, provided the basis for developing four alternatives which were compared, evaluated, and ranked. Capital and operating costs were evaluated for each of these alternatives and played a major role in the final alternative ranking. The alternative determined most viable for implementation in Monroe County was Alternative System No. 4 (Lime Stabilization and Mechanical Dewatering). Preliminary estimates indicate that the capital cost of this alternative would be in the $261,100 range, with annual operation and maintenance costs in the $58,200 range. Ranking second and third respectively were Alternative System No. 1 (Lime Stabilization and Sand Drying Beds) and Alternative System No. 2 (Mechanical Dewatering and Confined Composting). The potential for trans- porting some or all of the sludge out of the County to the new Dade County South District Regional Wastewater Treatment Plant was also identified. Negotiations between Dade and Monroe Counties regarding possible disposal fees and delivery restrictions, will be required before the viability of this alternative can be assessed. The proposed system should satisfy FDER's requirement to significantly reduce the negative environmental impacts of the present system of lagooning sludge on the landfills. This reduction will be accomplished by stabilizing and dewatering the sludge prior to final disposal in the sanitary landfill. This system also provides a means for utilizing the existing modular controlled -air incinerators to further reduce the volume of sludge to be landfilled at some future date. 404/C060983 Charles Aguero, Manager June 9, 1983 Page two We appreciate the chance to provide engineering services for this important and challenging project, and the assistance provided by you and your staff in preparing this report. We are available to answer questions or to discuss any portion of the report at your convenience. Sincerely, POST, BUCKLEY, SCHUH & JERNIGAN, INC. Kevin Cooley, P.E. Solid & Hazardous Waste Group Manager DRM/as 4ni-sm nn Dan R. Morrical, P.E. Project Manager 404/CO60983 TABLE OF CONTENTS Section Title Page Letter of Transmittal ii Table of Contents iv List of Tables vi List of Figures vi Glossary vii 1 INTRODUCTION 1- 1 1.1 Background 1- 1 1.2 Authorization 1- 3 1.3 Purpose and Study 1- 3 2 WASTE STREAM ANALYSIS 2- 1 2.1 Types and Sources of Sludge 2- 1 2.2 Present Quantities of Sludge 2- 2 2.3 Future Quantities of Sludge 2- 3 2.4 Characteristics and Composition of Sludge 2- 5 3 EVALUATION OF UNIT PROCESSES 3- 1 3.1 Pretreatment Options 3- 1 3.2 Process Options 3- 5 3.3 Disposal Options 3-18 3.4 Summary 3-20 4 ALTERNATIVE SYSTEMS 4- 1 4.1 Introduction 4- 1 4.2 Concept Design Considerations 4- 2 4.3 GTP Separation System 4- 4 4.4 Alternative No. 1 4- 5 4.5 Alternative No. 2 4- g 4.6 Alternative No. 3 4-14 4.7 Alternative No. 4 4-18 4.8 Regulatory Requirements 4-20 iv 404/061083 TABLE OF CONTENTS Section Title Page 5 CAPITAL AND OPERATING COST ESTIMATES 5- 1 6 FINAL ALTERNATIVE EVALUATION/RANKING 6- 1 6.1 Description of Matrix Evalua- tion System 6- 1 6.2 Assigning "Alternative Ratings" to Alternatives 6- 1 6.3 Evaluation Results 6- 5 7 FINDINGS, CONCLUSIONS AND RECOMMENDATIONS 7- 1 APPENDIX A - Itemized Cost Estimates and Staffing Plans APPENDIX B - STPs Hydraulically Capable of Accepting Sludge Treatment Facility Effluent REFERENCES v 404/L061083 LIST OF TABLES Table Title Page 2-1 MONTHLY QUANTITIES OF MIXED SLUDGE RECEIVED AT THE CUDJOE KEY AND LONG KEY LANDFILLS 2- 3 2-2 SLUDGE QUANTITIES BY TYPE, 1982 2- 4 2-3 SLUDGE PROJECTIONS- 2- 6 2-4 SEPTAGE CHARACTERISTICS AND COMPOSITION 2- 7 4-1 DESIGN FLOW ESTIMATES 4- 3 5-1 COST SUMMARY 5- 2 5-2 PROJECTED COST ESTIMATE SUMMARY 5- 3 6-1 MATRIX RANKING OF ALTERNATIVES 6- 6 LIST OF FIGURES Figure Title Page 1-1 MONROE COUNTY SANITARY LANDFILLS 1- 2 3-1 AVAILABLE SLUDGE PROCESS AND DISPOSAL OPTIONS 3- 2 3-2 PREFERRED SLUDGE PROCESS AND DISPOSAL OPTIONS 3-21 4-1 ALTERNATIVE 1 - FLOW DIAGRAM 4- 6 4-2 ALTERNATIVE 1 - PLAN LAYOUT 4- 7 4-3 ALTERNATIVE 2 - PLAN LAYOUT 4-10 4-4 ALTERNATIVE 2 - FLOW DIAGRAM 4-13 4-5 ALTERNATIVE 3 - FLOW DIAGRAM 4-15 4-6 ALTERNATIVE 3 - PLAN LAYOUT 4-17 4-7 ALTERNATIVE 4 - FLOW DIAGRAM 4-19 4-8 ALTERNATIVE 4 - PLAN LAYOUT 4-21 7-1 STPs HYDRAULICALLY CAPABLE OF ACCEPTING SLUDGE TREATMENT FACILITY EFFLUENT 7- 8 404/L061083 Vi GLOSSARY BOD5 5-day Biochemical Oxygen Demand - The oxygen used in 5 days to meet the metabolic needs of aerobic microorganisms in water rich in organic matter. COD Chemical Oxygen Demand EPA Environmental -Protection Agency FDER Florida Department of Environmental Regulation gpd Gallons per day Grease Trap A device that precedes a septic tank or sewer line and captures the majority of the grease from the waste stream. These devices are typically used by restaurants and gas stations. GTPs Grease trap pumpings MGD Million gallons per day Mixed Sludge Combination of STP sludge, septage, grease trap pumpings, and portable toilet pumpings. PTPs Portable toilet pumpings. SDBs Sand drying beds Septage Sludge from septic tanks STP Sewage treatment plant 0&M Operation and Maintenance 404/TO61083 vii Section 1 INTRODUCTION 1.1 BACKGROUND Prior to August 1982, Monroe County accepted liquid sludge for disposal at County landfills at no charge. However, with the realization of the rising costs to comply with more stringent sludge disposal regulations developed by the Florida Department of Environmental Regulation (FDER), the County ini- tiated a $0.02 per gallon charge in August 1982 for disposal of liquid sludge* received for disposal at the County landfills. Currently a mixture of liquid sludges from a variety of sources including sewage treatment plants, septic tanks, grease traps and portable toilets are received and disposed via lagooning at the Long Key and Cudjoe Key Sanitary Landfills. The County also had disposed of liquid sludge via lagooning at the old Key Largo Sanitary Landfill until it was closed in January, 1982. The new landfill now being operated by the County at a different site in Key Largo began accepting liquid sludge in May 1983 to eliminate the load at the Long Key site. Figure 1-1 shows the approximate location of the County's three operating sanitary landfills. A number of conditions existing in Monroe County make processing and environ- mentally safe disposal of liquid sludge particularly difficult and expensive. The average annual rainfall throughout most of the County is over 40 inches per year, thereby hampering conventional atmospheric sludge drying. Land is scarce and has a high groundwater table, porous soils and sensitive underlying geology. All existing sewage treatment plants in the County are smaller than 0.40 million gallons per day (MGD), making it difficult for them to accept liquid sludge without the potential for upsetting their treatment processes. At times, as much as 51 percent of the total liquid sludge generated in the County is unstabilized septage, and most of the sludge now delivered to the landfill has a very low solids content (3 percent and less). FDER has required the County to plan and implement a new method of liquid sludge disposal by an alternate method (other than the current lagooning 404/M061083 1-1 J } Y J J ti W I r o� LL r cc O z J G Z WJ W 0 S Y O I c� J W J Q 0Z 6 Q ZOO J J 'J } r Q Q Z Q O O U Q a W 0 i O J WJ cc > Z LL �Y� O U U, •0 W 3 } W ,Y 1-2 method) and has required, as a condition of the landfill operating permits, that a schedule be developed for construction of an alternate sludge disposal system by October 1983. This report completes the first phase toward this end to be followed by report review and authorization to proceed by Monroe County, final design, procurement, and permitting. 1.2 AUTHORIZATION In October 1982, Monroe County contracted with PBS&J to prepare this Sludge Management Study called for in Phase I of the program described above. 1.3 PURPOSE AND SCOPE The purpose of this Sludge Management Study is to identify and evaluate alter- natives to the County's present liquid sludge lagoon disposal system operating at their existing sanitary landfills and recommend the best available system for implementation. This study is the first step to providing the residents and visitors of Monroe County with an environmentally acceptable and cost effective system for disposing of liquid sludge generated within the County. The study begins by identifying and evaluating the composition, characteris- tics and quantities of the mixed liquid sludge stream currently being disposed at the Monroe County sanitary landfills. Projections of this data are then made over the next ten (10) years. Available methods of sludge processing and disposal are then identified in Section 3 through a literature search and evaluated based on their adaptability to the conditions and situation in Monroe County. Utilizing the preferred processing and disposal methods, alternative sludge management systems are developed, evaluated and compared in Section 4 to select four alternative systems for further investigation. Preliminary construction and operating cost estimates for these four selected alternative systems are presented in Section 5 and then further evaluated and ranked in Section 6. The conclusions and recommendations are then presented in the final section based on the study findings. 404/M061083 1-3 Section 2 WASTE STREAM ANALYSIS 2.1 TYPES AND SOURCES OF SLUDGE Liquid sludges received at the County Landfills are generated by four major sources: (1) sewage treatment plants (STPs); (2) septic tanks; (3) grease traps; and (4) portable toilets. Septic tank sludges are generated by both residential and commercial establishments. Permit records from the Monroe County Health Department indicate that 154 package STPs exist in Monroe County with a total design capacity of 3.930 MGD. These records also show that only 132 of these plants are currently in opera- tion for a total operating design capacity of 3.434 MGD. The plant design treatment capacities of the STPs in Monroe County range from 2,500 gpd to 400,000 gpd. Only 19 out of the 154 plants have a design capacity of 50,000 gpd or greater. Seven private sludge haulers presently collect liquid sludges and transport them to the County landfills for disposal. Their company name, truck capa- cities, and the approximate percentage of the total sludge that each delivered to the County landfills during the period of August 1982 to December 1982 are listed below. Company Name Captain Kidd's Sani Service Carter & Sons Septic Caribbean Septic Service Enoch Mitchell Jewell's 'Sani Service Quick Clean Septic Tank Service Scaffolds of Florida Percent of Total Sludge Truck Delivered to Capacity Landfills (gallons) M 2,000 17.9 1,500 13.9 Unknown 0.4 2,000 14.4 3,000 & 41.7 2,000 400 10.9 Unknown 0.8 TOTAL 100.0 404/N061083 2-1 2.2 PRESENT QUANTITIES OF SLUDGE When the sludge haulers enter and leave Monroe County landfills their trucks are weighed to determine the net weight of material deposited at the facility. This weight data is then mathematically converted to gallons and recorded. Based on available landfill weight records, Table 2-1 shows the quantities of sludge received at the Monroe County landfills from August 1981 through Novem- ber 1982. To determine an annual total and monthly average, data from Dec- ember 1981 through November 1982 is used. During this period, the Cudjoe Key Landfill accepted an average of approximately 21,300 gallons of liquid sludw per month and 29,300 gallons during the peak month. The Long Key Landfill received an average of approximately 104,800 gallons per month and 190,750 gallons (luring the peak month. The monthly average quantities provide an indication of the quantities of sludge that can be expected in an average month while the peak quantities provide a basis for processing/disposal system design. During the two months of November and December 1982, Monroe County staff conducted a survey under the direction of PBS&J to catagorize the liquid sludge received at the County landfills according to the source generating it. The quantity breakdown percentages determined by this survey for each sludge type were then multiplied by the average and the peak monthly values from Table 2-1 to estimate the monthly average and the peak quantities of each of the four sludge types delivered to the landfills. The survey results for each of the four sludge types are shown in Table 2-2. The survey reveals that the majority of the incoming sludge during the survey period was septage (51%). 2.3 FUTURE QUANTITIES OF SLUDGE The Monroe County 201 Faciliites Plan recommended that a six -plant configura- tion be built to provide centralized facilities for most of the County. In the summer of 1977, the County, FDER, and EPA agreed to defer the plan until substantial data was available to prove that the current effluent disposal practices represent a threat to public health or the environment. The County still feels the current sewage treatment system will not be changed for several 404/NO610133 2-2 i19.1:31 August September October November December January February March April May June July August September October November Annual) Total Avg. (1) Peak Table 2-1 MONTHLY QUANTITIES OF MIXED SLUDGE RECEIVED AT THE CUDJOE KEY AND LONG KEY LANDFILLS CUDJOE KEY LONG KEY GALLONS POUNDS 1981 GALLONS POUNDS * * August 66,249 596,240 * * September 30,401 273,610 * * October 61,522 553,700 12,444 112,000 November 52,950 476,550 26,378 237,400 December 60,806 547,250 25,771 231,400 January 101,499 913,490 29,304 263,700 February 110,462 994,160 19,673 177,060 March 190,752 1,716,770 19,953 179,580 April 141,353 1,272,180 20,589 185,300 May 86,674 780,070 20,504 184,540 June 107,282 965,540 26,380 237,420 July 138,002 1,242,020 21,930 202,860 August 68,544 615,540 17,710 163,820 September 77,829 719,920 10,298 95,260 October 57,452 531,448 16,615 153,680 November 117,280 1,084,840 255,105 21,259 29,304 2,312,020 192,668 263,700 Annual) Total Avg. (1) Peak 1,257,935 104,828 190,752 11,383,228 948,602 1,716,770 Total average for both landfills = 126,087 gallons/month (use 126,100 gallons/ month). Total peak for both landfills = 220,056 gallons/month (use 220,060 gallons/ month). * No weight data available. (1) Data from 12/81 through 11/82 is used to determine the annual total and the monthly average. 404/NO61083 2-3 Table 2-2 SLUDGE QUANTITIES BY TYPE Total Liquid Sludge STP Sludge Septage PTPs GTPs Recorded %(1) 100 28 51 1 20 Gallons Per Month Cudjoe Key: Average: 21,259 5,950 10,840 2,130 4,250 _ Peak: 29,304 8,200 14,950 2,930 5,860 , Long Key: Average 104,828 291350 53,460 10,480 20,970 Peak: 190,752 53,410 97,280 19,080 38,150 TOTAL(2) Average 126,100 35,310 64,310 1,260 25,220 Peak 220,060 61,620 112,230 2,200 44,010 (1) Average of the two month survey (11/82 - 12/82). (2) Totals rounded. 404/N061083 2-4 years. Therefore, for the purpose of projecting liquid sludge quantities requiring disposal, this study will assume that the consolidated sewage treat- ment system proposed under the 201 Plan will not be implemented during our ten year study period. If in the future the County decides to follow the 201 Plan recommendation, the time period required to plan and construct the regional treatment system would allow ample opportunity to reevaluate the sludge man- agement program. The 1982 average and peak quantities for total liquid sludge are projected over the 10 year study period (1982-1992) in Table 2-3 at a rate of increase equal to anticipated increases in population in the Monroe County area. 2.4 CHARACTERISTICS AND COMPOSITION OF SLUDGE The characteristics and composition of the waste stream must be considered in order to treat and dispose of the waste in the most effective manner. The sludge breakdown in Table 2-2 indicates that the liquid sludge being lagooned in the Monroe County landfills consists of a large quantity of septage (i.e., 51% in the two -month survey conducted). Typical concentrations of various constituents in septage are shown in Table 2-4. The composition and characteristics of septage vary significantly, making septage difficult to treat consistently. Even though the septic tank is designed to treat wastewater via an anaerobic digestion process, septage is more appropriately considered a highly concentrated wastewater rather than a stabilized sludge because it ranges from partially to completely digested (stabilized). Septage often has highly offensive odors and will have solids concentrations which vary from very low (1-2 percent) to approximately 10 percent. The large variation in solids content is due to the performance of the septic tank, the frequency of pumping, and the amount of groundwater infiltration into the septic tank. Toxic materials contamination is typically not a problem with domestic septage, but could be a very significant problem when dealing with commercial and industrial septage. Toxic materials con- tamination of septage should not be a problem in Monroe County since no major producing industries have been identified in the County that normally would dispose of a toxic effluent at Monroe County landfills. 404/NO61083 2-5 O o 0 ri LO Ln ro O N M Q w w O 4 mt LO a (A O CL- E 1— \ C9 r O O O ro N 00 LO CD N O 00 i a) Lc; 1: 00 > N N N O to N ro N M Ln L N +� N N N C t/1 O d � F- \ Ll O r O O O ro ro to LO -Rd- C 5 S- N M ct' O O O M C11 O ro N L CLO. N O 00 4-) r1 N N C r-1 1-4 .--4 O O cm ro \ i-f y a- r O O O (L) to er 00 to C'3 S- M O LA � w > C)1 M to t0 t� CD N QO1 tot0 -4 et t0 O rn +� to to 1l- � C � O r � N \ C1 O O O r-4 -4 O drro M Cn d s- > M M O O O %0 LO ko O N O N O to .� L N M LLB 4J N N N r C CIO O S r\ O CD CD CDro O 00 1l- +- r ro 1-1 M N Q ro s- w w 1- CD N tD Ln ct > N M d i N 1� N ro 00 00 m O CT CT Q1 r♦ r1 404/Q061083 2_6 Table 2-4 SEPTAGE AND CHARACTERISTICS AND COMPOSITION (1) Parameter EPA average Concentration (mg/1) Minimum Reported (mg/1) peak Reported (mg/1) Variability(2) Total So lids 38,800 1,132 130,475 115 Total VS 25,300 4,500 71,402 16 Total SS 13,300 310 93,378 301 VSS 8,700 3,660 51,500 14 BOD5 5,000 440 78,600 COD 42,900 1,500 703,000 469 + TOC 9,900 1,316 96,000 73 TKN 680 66 1,900 29 NH -(N) 160 6 380 63 NO3- 0.7 0.1 1.3 13 NO2 3.2 0.1 11 110 To3ial P 250 20 760 38 PO 64 10 170 17 Alkalinity 1,020 522 4,190 8 Grease and Oil 9,100 604 23,368 39 pH (units;) 6-9 1.5 12.6 8 Aluminum (Al) 48 2 200 100 Arsenic (As) 0.16 0.03 0.5 17 Cadmium (Cd) 0.71 0.05 10.8 216 Chromium (Cr) 1.1 0.3 3.0 10 Copper (Cu) 6.4 0.3 34 113 Iron (Fe) 200 3 750 250 Mercury (Hg) 0.28 0.0002 4 20,000 Manganese (Mn) 5.0 0.5 32 64 Nickel (Ni) 0.9 0.2 28 140 Lead (Pb) 8.4 1.5 31 21 Selenium (Se) 0.1 0.02 0.3 15 Zinc (Zn) 49 33 153 5 (1) Source: United States Environmental Protection Agency. Septage Manage- ment. Office of Research and Development. Cincinnati, Ohio. EPA-600/8-80-032. August, 1980. (2) Variability: Ratio between peak and minimum reported values. 404/NO61083 2-7 The second', greatest quantity of liquid sludge received at the landfills during the two -month survey was generated by STPs. According to the County Health Department. and DER records, all of the STPs currently operating in Monroe County are package plants that utilize some modified activated sludge process to treat sewage. Most of the facilities are small and use the extended aera- tion treatment method while the larger package plants (greater than 0.02 MGD) usually employ contact stabilization. All of the STPs have aerobic digesters to stabilize their sludge. Aerobically digested sludge is brown to dark brown and has a flocculant api pearance. If aerobically digested sludge is completely digested, its odor is not offensive; it is often characterized as musty. Stabilization reduces the number of pathogens in the sludge to a low level. The dry solids content of aerobically digested sludge ranges from 0.75 percent to 2.50 percent with a typical concentration of 1.25 percent. Significant contamination of these sludges by heavy metals and toxic compounds has not been reported as a problem to date in Monroe County as could be expected since no heavy industrial dis- charge sources have been identified. Grease traps are placed ahead of septic tanks or outlet sewer lines. If the grease traps work properly, they collect only detergent and grease. However, GTP waste characteristics can vary widely depending on the age of the GTPs and dumping practices of the grease trap user. The grease can be in either a liquid or solid (old grease) form. It has been reported that the grease traps in Monroe County normally contain from 75 to 95 percent water. Portable toilet pumpings (PTPs) are chemically stabilized and deodorized. A biodegradable formaldehyde solution is commonly used to disinfect and stabi- lize these toilet wastes while stored on -site. Typically, the solution also contains dye, perfume, detergent, and buffering agents. Wastes are pumped from the toilets frequently (about once per week). If the toilet wastes are pumped less frequently, the chemical solution will likely breakdown to the point where it is no longer effective in controlling odors. 404/N061083 2-8 Raw concentrated human wastes which accumulate in portable toilets have a high oxygen demand, (i.e., 5-day Biochemical Oxygen Demand (BOD5) concentrations ranging between 8,000 and 10,000 mg/l, and Chemical Oxygen Demands (COD) con- centrations ranging between 20,000 and 25,000 mg/1). The formaldehyde solu- tion also exerts a BOD5 of approximately 2 mg/l for each mg/l of formaldehyde. Since formaldehyde BOD5 is reduced as the portable toilet fills, the BOD5 of the wastes is only increased by less than 10% by the formaldehyde. This low percentage only occurs when a full portable toilet is pumped(1). Since the portable toilets are pumped once a week and can be less than full, a higher formaldehyde BOD5 can result. One Florida PTPs hauler reported that from a settling column analysis about 800 ml of PTP solids would settle out of 1,000 ml of PTPs and that about 150 ml of raw sewage solids would settle out of 1,000 ml of raw sewage. Therefore„ PTPs are about 5.5 times more concentrated than raw sewage. PTPs normally contain a large number of rags and debris, but a low concentration of grit. If the chemical solution used in PTPs is nonbiodegradable it could be detri- mental to a biological treatment process used for reduction and further stabi- lization of these sludges. However, the biodegradable formaldehyde currently used in the PTPs delivered to the County landfills should have little or no impact on a biological treatment process. The age of the sludge/chemical solution when disposed and the dilution effect of combining the PTPs with one or more of the other sludges also reduces the possible detrimental effects to a biological treatment process. In Monroe County portable toilets are supplied by two rental companies, Able and Scaffolds. Able does not landfill any of the PTPs it collects. A major- ity of Able's rentals are used on the Naval Air Station and the PTPs are dumped into the Navy Is Boca Chica STP. Able transports the PTPs collected outside of the Naval Air Station to a STP in Virginia Key, Dade County. Scaffolds, based in Key Largo, dumps PTPs in the Long Key Landfill. They use a formaldehyde base chemical solution which is purchased from Zep Co. in 404/N061083 2-9 Miami. Scaffolds initially pumps 5 gallons of the formaldehyde solution into each portable toilet before it is used; therefore, no digestion of the waste should occur, since the formaldehyde has disinfectant and preservative charac- teristics. In Florida, the capacity of portable toilets range from 30 to 70 gallons. The quantity and characteristics of the liquid sludge stream presently being received at the Monroe County landfills are highly variable due to the follow- ing factors: ° The percentage of each type of sludge in the hauler's trucks varies. ° The composition of septage is highly variable. ° Grease traps are sporadically pumped. ° Sometimes the aerobically digested STP sludge turns anaerobic. ° The degree of digestion of the STP sludge delivered to the landfill varies significantly. 404/N061083 2-10 Section 3 EVALUATION OF UNIT PROCESSES Sludges generated from sewage treatment plants (STPs), septage from septic tanks, potable toilet pumpings (PTPs) and grease trap pumpings (GTPs) usually require processing to insure ultimate disposal in an environmentally safe manner. The treatment processes and disposal methods available for these are categorized graphically by EPA and reproduced in Figure 3-1. Nine categories of process options and two categories of disposal options are considered for application to the mixed sludge stream currently received at the County land- fills. The available types of pretreatment, process, and disposal options are described briefly below. 3.1 PRETREATMENT OPTIONS Pretreatment is an initial process that prepares a sludge in some manner which will optimize the efficiency of the process options shown in Figure 3-1. 3.1.1 Screening Screening is a pretreatment step that removes the coarse and settleable solids like rags, glass, plastic objects, roots, etc., from the waste stream. Remov- ing the large objects protects pumps, pipelines, and other equipment from clogging or damage. Typical screening devices are racks or screens. Racks are parallel bars or rods. Screens are usually a wire mesh or a perforated plate. Either type of screening device can be hand cleaned or mechanically cleaned. Screens usually have smaller openings than bar racks; thus, screens collect more of the smaller incoming material. Very fine screens remove a significant fraction of suspended solids and BOD5 thus reducing the load on the subsequent treatment processes (2). Septage and PTPs would require screening before any type of treatment process. STP sludge probably would not, since it has already been screened. 404/0061083 3-1 PROCESS OPTIONS THICKENING STABILIZATION DISINFECTION CONDITIONING DEWATERING If i DAF GRAVITY CENTRIFUGE LIME CHLORINE ANAEROBIC DIGESTION AEROBIC DIGESTION HEAT DRYING FLASH ROTARY TOROIDAL SOLVENT EXTRACTION MULTIPLE EFFECT DISPOSAL OPTIONS UTILIZATION RESOURCE RECOVERY AGRICULTURE FOREST LAND RECLAMATION CHEMICAL HEAT IRRADIATION HIGH TEMPERATURE PROCESSES INCINERATION STARVED -AIR COMBUSTION WET AIR OXIDATION THERMAL CHEMICAL PHYSICAL ELUTRIATION COMPOSTING CONFINED UNCONFINED DISPOSAL ON LAND LANDFILL DEDICATED LAND DISPOSAL PERMANENT LAGOONS VACUUM FILTER BELT "FILTER FILTER PRESS CENTRIFUGE DRYING BEDS DRYING LAGOONS STRAINERS MISCELLANEOUS CONVERSION PROCESSES CHEMICAL FIXATION ENCAPSULATION EARTH WORM CONVERSION SOURCE: EPA SLUDGE TREATMENT AND DISPOSAL PROCESS DESIGN MANUAL. m 0 AVAILABLE SLUDGE PROCESS FIGURE ■ ■ AND DISPOSAL OPTIONS 3-1 f 136-1282h 3-2 3. 1.2 Gri ndi nq Grinding reduces the large, coarse solids in the waste stream so the pumps, pipelines, etc. are protected from clogging or damage. Therefore, grinding can substitute or be used along with a screening process. Only septage and PTPs would require grinding, for the same reasons they require screening. 3.1.3 Grease Removal The term "grease", as commonly used, includes the fats, oils, waxes, and other related constituents found in wastes. Septage can contain high concentrations of grease, especially septage from restaurants, shops, and gas stations. When haulers pump out grease traps from restaurants (typically every other month in Monroe County), the grease concentration in the collected wastes is exception- ally high. Grease interferes with biological activity and causes operational and maintenance problems in most systems. Therefore, removal of grease prior to processing of septage is usually necessary. STP sludge would not require a degreasing process, since the majority of the grease has already been removed. Likewise, PTPs do not usually contain grease. Grease can be removed from septage and GTPs by allowing the lighter grease to float to a water surface and be skimmed off. This can be accomplished in a separate skimming tank or in any unit process that has sufficient detention time and would accommodate grease removal operations. Detention times re- quired may be extremely long when grease is mixed with other sludges. High doses of chlorine break up grease. One potential problem with this method, however, is that it produces chlorinated hydrocarbons. EPA is cur- rently investigating the environmental effects of chlorinated hydrocarbons because they may be carcinogenic. 3.1.4 Equalization Since the strength and flow of the mixed sludge from the haulers in Monroe County vary greatly, a flow equalization tank would be needed. Flow equaliza- tion is the damping of flow rate variations so that a constant, or nearly 404/0061083 3-3 constant, flow rate is achieved. This would optimize the performance of the downstream process because it would not be necessary for the system to contend with shock loadings. 3.1.5 Grit Removal As mentioned in Section 2, septage contains large quantities of grit which should be removed prior to further process treatment. The amount of grit in STP sludcle and PTPs is not significant. Therefore, these sludges would probably not require degritting. Grit chambers are designed to remove grit consisting of sand, gravel, cinders, or other heavy solid materials that have specific gravities substantially greater than those of the organic putrescible solids in the wastewater. Grit also includes large organic particles such as food wastes. Grit chambers are provided -to protect moving mechanical equipment from abrasion and accompanying abnormal wear and to reduce formation of heavy deposits in pipelines, channels, and conduits. The efficient removal of grit is essential ahead of centri- fuges, heat exchangers and high-pressure diaphragm pumps. On the other hand, where untreated sludge is to be dewatered on vacuum filters and incinerated, less efficient grit chambers have given satisfactory service (2). Grit can be disposed in a landfill or incinerated and landspread. There are two general types of grit chambers: horizontal -flow and aerated. In the horizontal -flow type, the flow passes through the chamber in a horizontal direction and the straight-line velocity of flow is controlled by the dimen- sions of the unit or by the use of special weir sections at the effluent end. The aerated type consists of a spiral -flow aeration tank where the spiral velocity is controlled by the dimensions and the quantity of air supplied to ` the unit. The small daily flows of septage expected in Monroe County allow for the use of a simplified variation of these two general types of grit chambers. A grit removal system utilizing a quiescent tank would be a less costly and simpler system to operate than a horizontal -flow or aerated system. There would also be less of an odor control problem than with the aerated system. 404/0061083 3-4 3.2 PROCESS OPTIONS 3.2.1 Thickening Thickening processes concentrate the liquid sludge to reduce the volume that must be subsequently treated or disposed. This decreases the capital and operating costs of subsequent processes. Depending on the specific process selected, thickening can also provide one or more of the following benefits: sludge blending, sludge flow equalization, and sludge storage. Gravity thickening is one type of thickening process. However, it would not be a desirable method for thickening the mixed sludge stream currently re- ceived at the Monroe County lagoons because of the poor settling characteris- tics of the older STP sludge, septage, and PTPs. Centrifuge thickening may incur clogging problems due to the fiber and grit content inherent in septage and PTPs, unless these materials are completely removed. Screening prior to this thickening method would be critical to the centrifuge unit operation. Dissolved air flotation (DAF) involves supersaturating sludge with air by placing the sludge/air mixture under high pressure in a closed tank, similar to the process used to carbonate soft drinks. As with soft drinks, when the high-pressure is reduced, the dissolved gas (air in the case of sludge) bub- bles out of the solution. These bubbles attach themselves to solids which are dissolved or suspended in the sludge liquid. This creates buoyant solids which float to the surface. The solids are then skimmed off and collected. DAF thickening is considered an attractive thickening option if odors can be adequately controlled. 3.2.2 Stabilization Stabilization processes change sludge into a form that is less putrescible and has a lower pathogenic organism content, thus little objectionable odor. De- 404/0042583 3-5 pending on the specific process selected, the stabilization process may pro- vide one or more of the following benefits: a decrease in the amount of organic solids present in the sludge, disinfection, sludge storage, and pro- duction of an auxiliary fuel (methane gas). Chlorine stabilization is eliminated from further consideration because of the possibility of forming toxic chlorinated hydrocarbons. Construction of a separate biological treatment facility (a conventional aerobic or anaerobic digester) is not considered viable for Monroe County, because the flow rates and characteristics of the septage, GTPs and PTPs vary significantly. Biological upsets can easily occur when the incoming waste is not constant. If a biological upset did occur, the treatment process would require several days or weeks to recover. According to EPA, package treatment plants can be expected to stabilize septage which is "slug dumped" at approximately 0. L of the plant design capa- city. This percentage is so low, because many package plants have been de- signed with a minimal excess flow when treatment capacity is compared to larger, built -in -place plants. Since the largest package plant is only 0.4 MGD, the expected average flow could not realistically be slug dumped in Monroe County. In plants with holding and metering facilities, septage may be bled into the sewage flow at considerably greater flows than would be attain- able if only slug dumping procedures were available.(3) Since all of STPs are small in Monroe County, addition of septage to a STP would have to be con- trolled with metering facilities. The package STPs in Monroe County currently utilize aerobic digestion for stabilization. With proper pretreatment and quantity regulation, it may be possible to utilize some of these existing STPs to stabilize septage and PTPs generated in the County. A small quantity of pretreated mix of septage and PTP's could possibly be metered into a STP without causing an upset if the dilution effect was great enough. According to EPA, septage can be disposed of in a STP by addition to either the liquid stream or the sludge stream. In either case, screening, degritting 404/0042583 3-6 and equalization are recommended. A statistically significant sampling and analysis program of several seasons of Monroe's septage should be conducted prior to deciding where in the STP process to apply the septage. This anal- ysis program should include: 0 solids loading 0 oxygen demand 0 toxic substances o foaming potential o nutrient loading (N and P), where required (3). EPA recommends that package treatment plants, like those in Monroe County, not be allowed to accept any septage into their liquid stream if their design capacity is less than 0.1 MGD. In Monroe County only three package STPs are 0.1 MGD or greater, Boca Chica Naval Air Station, City of Key Colony Beach Municipal Treatment Plant, and Landings of Largo. The Boca Chica's design capacity is 0.4 MGD. It's average flow has been between 0.2 - 0.3 MGD depending on the season. The Boca Chica facility has existing sand drying beds and has plenty of land for expansion. The plant operator felt it could probably handle an additional 5% septage flow. The disadvantages of Boca Chica's plant are the very strict government con- tracts and periodic biological upsets. The Navy's southern division of the commercial utilities service stated that two types of contracts could be negotiated (i.e., buying treatment service or obtaining a license to operate the STP). Monroe County could buy the treatment service only on a temporary basis, 1-3 years. With a license, provisions can be added to the contract of the license to allow the County to expand. However, the Navy can revoke the license at any time' if they give 30 days notice to the County. To obtain either contract Monroe County would have to demonstrate that the project with the Navy -is the only practical alternate, is in the nation's interest, won't hamper mobilization, and is highly justifiable. 404/0042583 3-7 Boca Chica's biological upsets are frequently caused by the Naval Air Sta- tion's airplane washing operation. This problem will continue unless the washing operation is modified or the wash water is pretreated. Since the County needs a permanent, reliable sludge management plan, the Navy's STP will be pursued only as a last resort. The City of Key Colony Beach has a municipal STP with a design flow of 0.4 MGD. The facility is already operating at or over the design capacity. It has three 25' x 50' sand drying beds. These drying beds are used to their fullest extent. Since the treatment and dewatering facilities are operating at capacity, the City's STP would not suit the County project's needs. The design flow for Landings of Largo is 0.1 MGD. Landings of Largo is a housing development which currently has 30 units constructed of the 300 units planned. Therefore, the STP's average flow is only about 0.005 MGD. The de- veloper thinks the STPs flow will be approximately 50% of its design capacity even when the development is complete, assuming year round occupancy. Since most of the home owners may be seasonal residents, the average flow will most likely be considerably less than 50% of design capacity. Since the current and projected flows of Landings of Largo's STP are so low, the future quan- tities of the County's anaerobic septage and PTPs would upset Landings of Largo's aerobic biological process. However, since the capacity of the STP will not be fully utilized, it could easily accept liquid by-products from a thickening and/or dewatering process. Landings of Largo STP site is located in the southeast corner of the develop- ment. U.S. Highway 1 runs adjacent to the STPs site and has a separate en- trance into the treatment facility. Therefore, the haulers would not have to drive through the housing development. One of the developers, Mr. Poppeliers, stated that the treatment site does not have much open area which would be needed for the treatment units. However, vacant land is available adjacent to the STP site. The developers would have to be assured that the project with the County would not jeopardize the development's growth and aesthetics. As mentioned previously, all the package plants in Monroe County have aerobic digesters which stabilize the sludge. EPA recommends that an initial septage 404/0042583 3-8 addition into an aerobic digester should be limited to approximately 5% of the existing sludge flow. Further additions of sludge should be gradual. The capacity of the aerobic digesters in Monroe County range from 2,000 to 15,000 gallons and the typical capacity is about 6,000 gallons. Assuming a detention time of 10 days, the sludge flow in the digesters is from 200 to 1,500 gpd. Therefore,, the septage and PTP design flow (1992 peak flow) of 6,040 gpd cannot be accepted in the sludge stream of any of the small digesters in Monroe County since a 120,800 gpd digester would be required. The addition of lime to the sludge will increase the pH to a point where pathogens will be reduced and biological degradation will cease, thus pro- ducing a stabilized sludge. However, any neutralization of the lime will cause a lowering of the pH; thus, biological degredation of the sludge could be reestabbl i shed. For the highly variable Monroe County sludges, lime addi- tion is recommended as a feasible stabilization process. 3.2.3 Disinfection Disinfection processes destroy or inactivate the pathogenic organisms. De- pending on the specific disinfection process selected, some degree of sludge conditioning may be attained. However, disinfection will not be considered further because either the potential viable sludge disposal methods do not require disinfection, or some degree of disinfection is achieved by other more viable sludge treatment processes. 3.2.4 Conditioning These processes are used to improve the water removal efficiency of certain sludge thickening and dewatering processes. Depending on the specific process selected, disinfection and/or limited stabilization can also be provided by conditioning. Thermal conditioning involves heating of wastewater sludge to temperatures of 350' to 400°F in a reaction vessel under pressures of 250 to 400 psig for periods of 15 to 40 minutes. According to EPA, thermal conditioning of waste- water sludges offers the following advantages: 404/0042583 3-9 o Except for waste -activated sludge, the process will produce a sludge with excellent dewatering characteristics. Cake solids concentra- tions of 30 to 50 percent are obtained with mechanical dewatering equipment. o Processed sludge does not normally require chemical conditioning to dewater well on mechanical equipment. o This process sterilizes the sludge, rendering it free of pathogenic organisms. o If done prior to incineration, the process will provide a sludge with a heat value of 12,000 to 13,000 Btu per pound of volatile solids (28 to 30 kJ/g). o This process is suitable for many types of sludges that cannot be stabilized biologically because of the presence of toxic materials. o This process is insensitive to changes in sludge composition. o No lengthy or elaborate startup procedures are required. The disadvantages of thermal conditioning include: ° The process has high capital cost due to the use of corrosion -resis- tant materials such as stainless steel in the heat exchangers. Other support equipment is required for odor collection and control and high-pressure fluid transport. o It requires supervision, skilled operators, and a strong preventive maintenance program. o It produces an odorous gas stream that must be collected and treated before release. o It produces side streams with high concentrations of organics, ammonia nitrogen, and color. o Scale formation in heat exchangers, pipes, and reactor requires acid washing (4). Thermal conditioning.is not recommended because the capital costs are extremely high for the small sludge quantities generated in the County; since Monroe County's incinerators do not recover energy, increasing the heat value of the sludge is not a major advantage; and cake solids acceptable for landfilling (15%) can be achieved without thermal conditioning. 404/0042583 3-10 Elutriation cannot be considered because it requires prestabilized sludge via anaerobic digestion which is not considered a viable process for this sludge stream. When the sludges' physical characteristics are changed in some manner, the process is called physical conditioning. Sludge can be physically changed by adding sand, mechanical screening, grinding, etc. The sand method of physical conditioning adds considerable inorganic bulk to the sludge and may interfere with biological processes. Inorganic chemical conditioning is used primarily with mechanical sludge dewatering. The chemicals most often used for conditioning of municipal sewage sludge are lime and ferric chloride. The ferric chloride promotes dewatering. Lime slightly improves dewatering characteristics, but it pri- marily provides pH control, odor reduction, and disinfection. Polyelectro- lytes, polymers, are widely used to promote dewatering. Chemical conditioning is considered the most viable conditioning option since it is the most flexible and is adaptable to varying sludge conditions. 3.2.5 Dewatering Dewatering processes reduce the volume of water present in the sludge, thereby, changing -its physical characteristics from being a liquid to a solid or semi- solid. The capital and operating costs of downstream treatment processes and disposal methods are correspondingly reduced. Mechanical dewatering processes (vacuum filter, belt filter, filter press, and centrifuge) require a conditioned sludge for efficient and economical opera- tion. Start-up and operational adjustments can be expected with mechanical dewaterincl equipment in conjunction with the changing character of the sludge. Sand drying beds can reduce the volume of the STP sludge by as much as 75 percent. Conditioned sludge is usually not necessary for dewatering in drying beds, but conditioning may be required for odor control when septage and portable toilet pumpings are dewatered using this process. The sludge product from drying beds is a nonfluid material ranging from 20 percent to 60 percent 404/0042583 3-11 solids content. A solids concentration of 20 to 30 percent is required to allow removal of the sludge from the drying beds mechanically while a 30 to 40 percent concentration is required to remove the sludge from the drying beds manually. When using sand drying beds, the filtrate from the beds should be collected using an underdrain system. This filtrate must then be processed through a STP or permitted for discharge. It is unlikely that this filtrate could be permitted for discharge without further treatment due to the high concentra- tion of BOD5, unless the filtrate could meet Chapter 17-3 Water Quality Stan- dards. Sand drying beds (SDBs) are currently being successfully used to dewater STP sludge in Monroe County. After telephone conversations with several of the plant operators in Monroe County and Key West, the following data are a good representation of the current practices of operating SDBs in that area: o The time required to achieve a "dry" cracked sludge cake varies between 3 to 20 days, depending on weather conditions, how well the sludge is digested and depth of the applied sludge. o When the sludge cake is "dry", it is removed manually with a rake and shovel. o The depth of the applied sludge is 1-2 feet. o The depth of the SDBs varies between 3 to 6 feet. o All SDBs pump the collected filtrate to the head of the sewage treatment plant. o Most of the sludge cake is utilized locally as a soil conditioner. o Some operators chemically treat the sludge before applying it to the SDB with chlorine, ferric chloride, alum, or hydrogen peroxide. EPA states that caking and cracking will generally occur when the solids content reaches 35 to 40 percent (5). Sand drying beds are natural dewatering processes and are the most widely used method of municipal sludge dewatering in the United States. This dewatering process is also a flexible process in that the beds can be used not only to 404/0042583 3-12 dewater sludge, but also to dry it to a solids concentration of greater than 50 to 60 percent by adjusting parameters such as bed thickness and process time. When land is available, sand drying beds can be economically attractive when compared to mechanical dewatering equipment. The use of sand drying beds is the preferred dewatering method because they are less sensitive to variable sludges, are less risky, can normally achieve higher percent solids than mechanical dewatering. The critical question that must be addressed when using drying beds in Monroe County is the availability of adequate land to implement sand drying bed sys- tems. The preferred location of sand drying beds would be adjacent to a STP which can be used to recycle the filtrate from the drying beds. The use of a cover over the drying beds can reduce the land requirements by one -quarter to one-half. Therefore, covered SDBs are recommended for Monroe County since land acreage must be minimized and the rainfall is over 40 inches per year in most locations. A design consideration when using drying beds is to provide adequate storage for periods of high precipitation and/or low evaporation rates. If the land required for SDBs cannot be found at an appropriate location, mechanical dewatering should be pursued since its land requirements are less than SDBs. Other types of "drying beds" have been developed, such as paved drying beds, wedge -wire filter beds, and vacuum assisted drying beds. The paved drying beds are immediately discounted from further consideration, because they re- quire more land and capital cost than the SDBs. The primary advantage of the paved bed is that there is less chance of damaging the underdrain pipes when sludge is mechanically removed. The wedge -wire and vacuum assisted drying beds may require slightly less land than SDBs but are capital intensive sys- tems. Because the sand drying system is currently being successfully used in the County, the drying bed system will be investigated later in the proposed system concept plans. Sludge drying lagoons are another method of sludge dewatering when sufficient, economical land is available. Sludge is placed at depths three to four times 404/0042583 3-13 greater than it would be in a drying bed. Generally, sludge is allowed to dewater before removal which might require one to three years. The cycle is then repeated. Large areas of lagoons can produce nuisance odors as they go through a series of wet and dry conditions. This dewatering method will not be pursued further due to the above disadvantages. Strainers, which can be effective for chemical and other nonbiological, non - colloidal sludges, are eliminated from further consideration as a dewatering device since they are not suitable for STP sludge, septage, and PTPs which are biological and/or colloidal type materials. 3.2.6 Heat Drying , Heat drying processes further remove moisture from dewatered sludges through evaporation. An additional benefit of drying is disinfection which renders nontoxic sludges suitable for beneficial utilization. The use of waste heat from the current solid waste incineration in Monroe County is a potential energy source for this process. Five methods of heat drying include the following: 1. Flash -Drying - The moisture of the sludge is rapidly removed by spraying or injecting the solids into a hot gas stream. The flash - drying process is based on three distinct components that can be combined in different arrangements. In the first component, the "wet" sludge cake (approximately 20% solids) is blended with prev- iously dried sludge in a mixer to improve pneumatic conveyance. The second component consists of hot gases possibly supplied by Monroe County's solid waste incinerators. The third component is the ef- fluent gas treatment facility or induced draft facility (4). 2. Rotary Dryers - Rotary dryers use a sloped rotating cylinder to move the material being dried from one end to the other by gravity. Direct, indirect, and direct -indirect rotary dryers have been used to dry sludge. Mechanically dewatered sludge is added to a mixer and blended with previously dried sludge to provide low moisture dryer -feed. Hot gas is added to the dryer, usually in a concurrent flow pattern. After the sludge has been held in the dryer for 20 to 60 minutes, the dried sludge is discharged. In the indirect dryers, the heat transfer is accomplished by contact of the wet solids with hot surface (i.e., a retaining wall separates 404/0042583 3-14 the wet solid and the heating medium). The vaporized liquid is removed independently of the heating medium. Indirect rotary dryers have not been used in the United States for drying sludge. In direct -indirect drying, the hot air or gas is recirculated to flow in direct contact with the drying sludge in addition to heating the metal drying surfaces (4). 3. Toroidal Dryer - The Toroidal (doughnutshaped) dryer is a relatively new dryer that is employed for sludge processing. The dryer works on a jet mill principle and contains no moving parts. Transport of solid material within _the drying zone is accomplished by high - velocity air movement. The system is composed of wet sludge storage, mechanical dewatering, sludge drying, air pollution control, final product finishing, and storage. The mechanical dewatering step is designed to deliver the dewatered sludge to the dryer at about 35 percent to 40 percent solids. The dewatered sludge is mixed with previously dried sludge to reduce the moisture concentration of the dryer feed. Heated process air is distributed through three manifold jets to the lower segment of the toroidal drying zone chamber. The air from one of the three jets is directed in such a way as to impinge upon the incoming wet feed material and propel this material into the drying zone, where particle size reduction and drying begins. Additional jets in the drying zone convey the material into the toroid for additional drying, grinding, and classifying (4). Since the three drying methods mentioned above require dewatered sludge, they are not practical for this project since the dewatered sludge could be directly landfilled, mixed with the landfill cover material, or coincinerated in the existing County's incinerators to provide sludge disposal at a much lower cost. 4. Solvent Extraction - The Basic Extraction Sludge Treatment (BEST) process is based on the use of an organic solvent to reduce the amount of water that must be evaporated in a conventional drying step. A fullscale BEST system has not yet been operated. A study team in Seattle, Washington determined that a pilot BEST process (1 gpm) was not cost-effective. In Los Angeles, it was also found to be one of the more expensive sludge disposal alternatives. This high-technology process is quite complex and may require a competent chemical engineer to insure efficient operation. There are a relatively large number of components in the system, hence, maintenance costs may be high. Unpleasant odors (ammonia -like) existed in the exhaust gas during the Seattle, Washington, study. A deodorization system may be required. Full-scale data on chemical and energy requirements, as well as operating reliability, are not currently available on the BEST system (4). 404/0042583 3-15 Because of the disadvantages mentioned above, the solvent extraction, heat drying method will not be utilized for this project. 5. Multiple -Effect Evaporation - EPA states that: The basis of economy for multiple -effect evaporation is steam reuse. Steam generated in the first evapo- rator (by evaporation of water from sludge) is used as the heating fluid in the second evaporator. The method is feasible if the second evaporator is oper- ated at a lower pressure than the first. The major steps in the process are oil mixing, multi- ple -effect evaporation, oil -solid separation, and condensate -oil separation (4). According to the manufacturer, over 65 installations are in opera- tion worldwide. Many of these systems have operated at industrial facilities in the United States. Engineers conclude that the pilot multiple -effect evaporation unit was a viable sludge drying process which offered considerable energy efficiency when compared to con- ventional direct and indirect contact dryers. However, it was recommended that a large-scale facility should be built and operated to conclusively demonstrate process reliability and economics (4). Since scale -up problems often occur, this drying process will not be considered for this project. 3.2.7 High -Temperature Processes Incineration and starved air combustion require a dewatered sludge product in order to minimize energy requirements of the process. These processes should only be considered in conjunction with coincineration with solid waste in Monroe County's existing incinerator units to be economically viable. Solid waste can be used as an energy source to evaporate moisture from the sludge cake to the point where the cake will burn and release its energy. The wet air oxidation process oxidizes liquid sludge which produces sterile, nonputrescible solids that are easily dewatered to a high solids content by conventional means (settling, centrifugation, or vacuum filtration). At high degrees of oxidation, the residual solids resemble ash from thermal incinera- tion. Sludge which is to be wet air oxidized needs to be thickened to four to s i x percent solids, but the percent solids should not be greater than 10. The basic components of the system are a sludge grinder, a high-pressure pump, a 404/0042583 3-16 heat exchanger, a reactor, steam, a vapor -liquid separator, dewatering equip- ment, treatment for the supernate, and air pollution control equipment. The waste heat; from the Monroe County incinerators could provide the heat energy to produce the steam, but the other components would need to be purchased at considerable cost. This process is, therefore, considered uneconomical for the small quantities of sludge generated in Monroe County. 3.2.8 Com osp ting Composting biologically decomposes sludge to a relatively stable and disin- fected form which is fairly well -suited for utilization as a humus -like soil conditioner. EPA says that, "sludge is not rendered totally inert by compost- ing. The composting process is considered complete when the product can be stored without giving rise to nuisances such as odors, and when pathogenic organisms have been reduced to a level such that the material can be handled with minimum risk." (4) Liquid sludge can be mixed with a highly adsorbent material, such as processed municipal waste or wood chips, and then composted, or the sludge can first be dewatered to a cake form, and then mixed with a bulking agent to assist in aerating -the sludge during composting. Some of the bulking agent could be extracted from the mixture following composting to prepare the product for marketing and be reused. Composting liquid sludge with solid waste generally produces a product that has an unstable market unless presorting of the solid waste is practiced. Composting has two major classifications, unconfined and confined. According to EPA unconfined processes are not enclosed, although a roof may be provided to protect the compost from precipitation. Unconfined processes make use of portable mechanical equipment such as front-end loaders or mixers for compost mixing and turning. There are two methods of unconfined composting. In the windrow method, oxygen is drawn into the pile by natural convection and turn- ing, whereas in the static pile method, aeration is induced by forced air circulation. Confined systems utilize a stationary -enclosed container or reactor for composting and are designed to minimize odors and process time by 404/004258.3 3-17 controlling conditions such as air flow, temperature, and oxygen concentra- ti on. (4) High rainfall conditions make Monroe County more suited for a con- fined or covered unconfined system. 3.2.9 Miscellaneous Conversion Processes The chemical fixation and encapsulation processes minimize the tendency of dewatered sludge to leach toxic or otherwise hazardous constituents into the environment when disposed in a landfill. Generally, these processes are ex- tremely expensive and utilized only when sludges cannot be landfilled or economically processed and disposed in some other manner, because of toxic or otherwise hazardous properties. These processes, therefore, would not be practical or economical for Monroe County's sludge stream unless other less capital intensive alternatives prove to be unacceptable. Conversion of sludge to earthworm castings, which are stable and useful as a soil conditioner, is not considered viable because this technology is largely unproven on a largescale over an extended period of time and because the market for the earthworm castings is not developed. 3.3 DISPOSAL OPTIONS 3.3.1 Utilization Four methods of beneficial use of sludge include the following: 1. Resource Recover - Dewatered sludge can be mixed with municipal solid waste and coincinerated for energy recovery. Energy is not currently being recovered from Monroe County's solid waste incinera- tors, making energy recovery through coincineration unlikely at this time. However, this could be a future possibility if the County develops an energy recovery plan for their existing incinerators. Although not listed as an option, composting sludge for use by the public and/or municipal use (e.g. gardens, lawns, golf courses, parks, etc.) is a viable option in Monroe County. 2. Agriculture - Municipal sewage sludge contains nutrients and organic matter which can make it valuable as a fertilizer or soil condi- tioner. 404/0042583 3-18 Fertilizer and soil conditioning products are used throughout the State of Florida. Sludge can be applied to land as a liquid or solid as compost, or as a component of commercial fertilizer mix- tures. This alternative will not be considered further because agricultural land is not abundant in Monroe County. Plus, the uncertainies regarding public acceptance and pathogenic or other contamination make this alternative questionable in Monroe County. 3. Forest - The nutrients and organic material in sludge applied to forest land are removed through soil processing and plant uptake. Forest application will not be considered further due to the lack of nearby usable forest land. 4. Land Reclamation - Sludge can supply the nutrients and soil -building material necessary to reclaim disturbed lands such as construction sites, strip-mined lands, gravel pits, and clear-cut forest. Since long-term commitments of public or private land are uncertain, land reclamation is not a viable disposal alternative. Furthermore, public opposition and potential health hazards make this disposal option unattractive in Monroe County. 3.3.2 Disposal on Land Methods used for land disposal of sludge include the following: 1. Landfill Disposal - According to DER's January 11, 1983 predraft #9 of Chapter 17-7 Part IV Section 17-7.53(6), dewatered sludge can be buried in a landfill by itself or in combination with refuse, if the solids content (by weight) is at least 15 percent. The final ruling of Chapter 17-7 Part IV has not been issued and will not be offi- cially final until probably mid 1983. Until the final ruling is published, the predraft is subject to changes. 2. Dedicated Land Disposal - Liquid sludge is heavily applied to land which has limited public access and which has been set aside solely for sludge disposal. The sludge application rate is normally lim- ited to the net soil evaporation rate (evaporation minus precipita- tion) to prevent groundwater and surface water contamination. This option will not be pursued due to the scarcity of land in Monroe County. 3. Permanent Lagoon - A layer of liquid sludge is placed in a lagoon where it is allowed to dry and further stabilize. After the sludge layer dries, another layer of liquid sludge is added until the lagoon is filled. The dried sludge in the lagoon can then be re- moved and the lagoon returned to service, or the filled lagoon can be covered and then abandoned. 404/0042583 3-19 Odor problems are expected with this disposal method because of the mixed sludge stream to be disposed. Lagooning may lead to con- tamination of groundwater or surface water. Disease vectors (e.g., flies and mosquitoes) may be created. Lined lagoons rely on evapo- ration for dewatering and are, therefore, not viable in Monroe County where annual rainfall exceeds 40 inches. For these reasons, permanent lagoons will not be considered further. 3.4 SUMMARY Figure 3-2 shows the unit processes considered to be potentially viable for processing/disposal of Monroe County's liquid sludge stream. These unit pro- cesses are combined into alternative processing/disposal systems and evaluated in Section 4. 404/0042583 3-20 PROCESS OPTIONS THICKENING STABILIZATION DISINFECTION CONDITIONING DEWATERNNG I DAF(� RAVIT CENTRIFUGE('b LIME CHLORINE ANAEROBIC DIGESTION AEROBIC ESTIO (a) ODOR CONTROLL SHOULD BE ADDRESSED Qb) SCREENING CRITICAL HEAT DRYING HIGH TEMPERATURE PROCESSES INCINERATION I STARVED -AIR I COMBUSTION (c) COVER REQUIRED IN MONROE COUNTY. DISPOSAL OPTIONS UTILIZATION (d) �A A CHEMICAL PHYSICAL ELLITRIATiON COMPOSTING r CONFINED UNC0NF1NE4c DISPOSAL ON LAND LANDFILL DEDICATED LAND DISPOSAL PERMANENT LAGOONS LEGEND: VACUUM FILTER BELT'FILTER FILTER PRESS CENTRIFUGE DRYING BEDS DRYING LAGOONS STRAINERS MISCELLANEOUS CONVERSION PROCESSES TION ...//iii POTENTIALLY VIABLE ELIMINATED FROM FURTHER CONSIDERATION (d) PUBLIC and/or MUNICIPAL USE OF COMPOST IS A VIABLE OPTION. SOURCE: EPA SLUDGE TREATMENT AND DISPOSAL PROCESS DESIGN :MANUAL. � I PREFERRED SLUDGE PROCESS FIGURE AND DISPOSAL OPTIONS 3-2 SBHWG fC-163—.0183A 3-21 Section 4 ALTERNATIVE SYSTEMS 4.1 INTRODUCTION Based on the selection of potentially viable "unit processes" for processing of liquid sludges in Monroe County in Section 3, this Section describes four alternative systems which could_ be utilized for treating and disposing of these sludges in an environmentally acceptable manner by combining unit processes. The four alternative systems being considered are as follows: Alternative No. 1 - Lime stabilization, dewatering by covered sand drying beds and land disposal at the County landfill(s). Alternative No. 2 - Mechanical dewatering and composting with final product use and/or disposal at the County land- fill(s). Alternative No. 3 - Mechanical dewatering and coincineration with municipal solid waste at the County incinerator plant(s). Alternative No. 4 - Lime stabilization, mechanical dewatering and land disposal at the County landfill(s). Due to the relatively small quantities of liquid sludges which would be re- ceived by the proposed treatment/disposal system, systems which are low capi- tal intensive and take advantage of existing available resources (i.e., the new County incinerator plant, existing STPs, etc.) were developed for consid- eration. Due to the incompatible nature and unique treatability characteristics of GTP wastes, these wastes are proposed to be segregated from the other liquid sludges (i.e., STP sludge, PTPs and septage) and treated in a separate separa- 404A/AO6883 4-1 tion system. The GTP separation system is the same for all of the alternative systems. 4.2 CONCEPT DESIGN CONSIDERATIONS A conceptual design was developed for each alternative assuming a 1992 average design year flow. The peak liquid sludge flow for this year was estimated at 11,620 gpd (see Table 4-1). As mentioned in Section 2, the County staff conducted a two month survey during the months of November 1982 and December 1982 under the direction of PBSU , which determined the percentages of the different types of sludge the County landfills received during that period. For design purposes, the highest monthly percentage determined from the two month survey is used to size the GTP process line and the liquid sludge pro- cess line of each alternative. The highest percentage of GTPs (38%) occurred during November while the highest percentage of liquid sludge without GTP (87%) occurred during December. In Table 4-1 these percentages are multiplied by the total liquid sludge flow to yield a design flow of approximately 10,000 gpd5 for 'liquid sludge without GTPs and 4,500 gpd5 for GTPs. The small quantities of sludge currently generated in the County make the initial construction of one central sludge processing facility, rather than two or three, the most logical and economical design choice for Monroe County. It is, therefore, assumed that one facility would initially be constructed in the Long Key area, which is relatively centrally located in the County and nearby the Long Key Incineration Plant and Sanitary Landfill. The facility would operate eight hours per day, five days per week. When it nears its design capacity (estimated to occur in the 1992 design year), a second facility could be constructed in a location that would optimize the reduction of haul costs, probably in the Key Largo area. Since the Long Key area is near a populated area, odor control, traffic control, aesthetic buffering and other measures which would make the facility compatible with its surrounding environ- ment should be a prime consideration in the design of the facilities. 404A/AO6883 4-2 Table 4-1 DESIGN FLOW ESTIMATES(1) DESIGN PEAK PERCENTAGE GAL/MONTH GPD5(3) Total Liquid Sludge(2) - 251,760 11,620 Liquid Sludge Design Flow (w/o GTPs) 87%(4) 219,030 10109 (10:000)(5) GTPs Design Flow 38%(4) 95,670 4,415 (4,500)(5) (1) Based on estimated maximum monthly flows for design year 1992. (2) From Table 2-4. (3) Gallons per day (GPD5) based on a five day/week operation. (4) Determined from the highest monthly percentage of total liquid sludge delivered to the County landfills during a two month survey conducted during November 1982 and December 1982. (5) Quantity used to estimate the size and capital cost of each alternative. 404A/AO6883 4-3 4.3 GTP SEPARATION SYSTEM As discussed in Section 3.1.2, potential operational problems can be avoided in a combined liquid sludge process system if the GTPs are received and handled separate from the other sludges. In a quiescent tank, grease will readily separate from water. This simple gravity/density separation technique is recommended to process GTPs in Monroe County. Two 4,500 gallon separation tanks could be used for this purpose. The tanks would be covered and the tank outlet vent would be equipped with an activated carbon filter for odor control. The tanks would have access port holes for regular cleaning and maintenance, Two tanks rather than one would be provided to provide continuous service so one tank can always accept GTPs while the other tank is being drained, cleaned, or repaired. A portable pump would be used to transfer GTPs from the delivery trucks into the separation tanks. A stationary pump would pump the water that has separated from the GTPs to the STP or to a storage tank. The separation tanks would be constructed of fiberglass, a material which is strong, compati- ble with a very high pH materials, won't corrode, doesn't need to be painted and isn't. subject to ultraviolet degradation. Generally, about 15 minutes detention time is required to adequately separate grease from the water in a quiescent separation tank. However, some tests should be conducted prior to the design/fabrication of these tanks to verify this detention time as optimum and to determine if interference caused by other constituents common to the grease -water mixture of GTPs is significantly affecting the separation time. Water which has a higher unit weight than grease separates to the bottom of the tank while the grease "floats" to the top. Since the conductivity of water and grease are different, a conductivity meter in the water drain outlet pipe line would be used to immediately indicate the presence of the grease/ water interface as the tank is emptied. When grease is detected, the outlet valve would be manually closed by the operator or automatically closed by remote instrumentation/control from the conductivity meter. This GTP separation system should be located at or nearby a STP so that the wastewater from the grease separation tank can be economically pumped to the STP for treatment and disposal. If the system can't be located at or near an 404A/AO6883 4-4 STP, an effluent storage tank would be required to store the wastewater until a tank truck hauls it to a STP. Separated grease would be periodically pumped out of the separation tank by a tank truck and either hauled to the working face of a County landfill for disposal or mixed with the solid waste and coincinerated at a County incinerator plant. 4.4 ALTERNATIVE NO. 1 Approximately 1.6 acres of land would be required to accommodate the facili- ties involved with this alternative system. Figure 4-1 is a process flog diagram for the system which shows its major unit processes. The system would accept mixed liquid sludge, septage, STP sludge, and PTPs with a solids content of less than 15 percent by weight. Sludges having a solids content of 15 percent by weight or greater would be hauled directly to a landfill for final disposal (not processed at this facility). Dewatered sludge cake from the process line would also be codisposed at a County landfill with solid wastes and incinerator residue. Filtrate (wastewater) from the drying beds would be diverted to an STP for treatment and disposal. Figure 4-2 shows one possible site layout for this system which provides an indication of space require- ments. Incoming liquid sludge haulers would hookup their tank trucks to a "quick connect" line. Liquid sludge from the tank truck would be pumped into a 6,000-gallon capacity lime stabilization tank. The "quick connect" provides an airtight connection between the hauler's line and the facility line which which should eliminate obnoxious odors during the unloading operation. Be- tween the "quick connect" and the influent sludge transfer pump, an in -line chopper will automatically pulverize large incoming particles to prevent clogging or damage to the influent pipe lines, the pump and other downstream components. Two "receiving stations" (quick connect line, in -line chopper and sludge pump) would be provided so that two haulers may simultaneously unload their tank trucks. The lime stabilization tank would be a completely -enclosed, water -tight vessel with an in -line activated carbon filter on its air vent for odor control. 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''?t:} •:yqt • a ••R '4 cr. i3••i`-•::..g'k i?i" ::}m.,S:rfi��{ �,,�}::::ui . R�;'rS• �~ ;: :`�':9!YG{�':::Yt?f:.Y.s". '...k E: s::;.±. x}"'•}::iv'sc`':,:tJ}%:::T: �: :.'s-d•" ).:: -:F twYt'�T' .;?a:.f•R >i I 8 r z > x m 0 O I r r Im 0 I 0 z = I Im co I I > v c� r C- m -+ zi > to m m *> G� c m� •4 C MV mm >M -4 a r. M z > >0 z — — — — -- — — —• — — — — — — — — — I require a slaking process. A submersible mechanical mixer would mix the lime and sludge. This adjustable mixer can be moved up and down as needed for the varying sludge levels in the tank. After the hauler's tank is empty, the system operator would check the level in the receiving tank, add a prede- termined amount of hydrated lime (corresponding to the level of sludge in the receiving tank) through an access porthole in the top of the tank and adjust the position of the mixer. After the lime and sludge are well mixed and the mixture has reached a pH of at least 12, the mixture would be automatically pumped into a 20,000-gallon stabli zed sludge holding tank. This holding tank would be a watertight, completely enclosed vessel but would not require an air vent filter for odor control since the sludge is stable. To monitor whether the sludge remains stable in this tank, an automatic pH meter should be used to continuously monitor the pH of the sludge. If the pH drops below 10, the operator can add an appropriate amount of lime to the sludge to restabilize the mixture. A porthole on top of the storage tank would be provided for this purpose and for periodic cleaning and maintenance of the tank. An automatic visual and/or audio alarm would alert the operator if the pH falls below 10 in the storage tank. Stabilized sludge would periodically be pumped from the holding tank to sand drying beds for dewatering. In order to insure that the stablized sludge is as homogeneous as possible when applied to the drying beds, to maximize the bed efficiency/performance, an adjustable mechanical mixer in the holding tank would be activated several hours before the sludge is distributed onto the bed. The sand drying beds should be covered with a transparent or opaque roof to maximize their dewatering efficiency. Percolate from underdrains in the SDBs would be collected in a wastewater lift station and pumped to a STP along with the wastewater from the grease separa- tion system for treatment and disposal. Dried sludge cake would be removed from the SDBs with a small front-end loader and transported to one of the County landfills for disposal. This cake can be landfilled directly or mixed with landfill cover material. It is unlikely that incineration of the dewatered sludge from this alternative would be feasible. The abrasive nature of the dewatered cake as a result of its high lime content and sand may be detrimental to the incineration units. 404A/A0688.3 4-8 4.5 ALTiERNATIVE NO. 2 Figure 4-3 shows the process flow diagram for this alternative system. Initially, a four -inch, positive displacement, diaphragm sludge pump would withdraw sludge from the hauler's delivery tank truck, through an in -line chopper and pump it into a 10,000 gallon quiescent, covered grit removal tank. Grit removal is needed to protect downstream components from excessive wear and to prolong their useful life. For conceptual design purposes, a four-hour detention, time was assumed for the grit removal tank, yielding a tank capacity requirement of 10,000 gallons to accommodate the daily design flow of 10,000 gpd assuming it could be received during a four-hour period. Periodically, settled grit would be pumped out of the bottom of the tank to a grit classi- fier where the grit is separated from the water and other lighter organic particles. Dry grit cake falls to the bottom of the inclined classifier and then into a dumpster with a lid. The water and light organic particles (supernatant) are pushed to the top of the classifier for removal. The cover on the grit classifier would be transparent. Since grit makes a distinctive noise when traveling through a pipe, the system operator will know by sight (transparent cover) and sound when the heavy grit has emptied out of the tank and will ;stop pumping from the bottom of the tank. The grit -free liquid sludge would be pumped into a 20,000-gallon storage tank by a second 4 inch positive displacement diaphragm pump. This intermediate storage tank could accommodate a 2-day down time in the system. It would be a completely enclosed watertight vessel equipped with an access porthole and a filtered air vent for odor control. A submersible mixer provided in the tank would maintain a circulating homogenous liquid sludge mixture. The mixer would be adjustable to move up and down as needed for the varying sludge levels in the tank. Degritted sludge would be withdrawn from the storage tank and fed to a filter belt press for dewatering to a solids content of at least 20% by weight. A one meter belt filter press (shown in the Figure 4-3) operating one shift (8 hr/day) per day could process the 1992 design sludge flow of 2,000 pounds of dry solids per day. This size press has a daily throughput capacity ranging from 1,600 lbs. to 4,500 lbs. assuming an 8 hr/day operation. The press would 404A/A06883 4-9 CA m 0 X Z 0-4 > m r- m n 0 -< 0 0 c z 2) 0 42 FT.-7' mc ma C) mm v< to 4 r- Z c rm* coo ro G) m > 0 z > z < Z > m m 0 M M m m titm fl 4 m rt) > mco m > v 0 to c .4 > Gi C) -4 '4 :4 z Z > 0 m M), > -4 > (A 10 C) 0 o > -4 m m 0 'a 0 0- ,4 > M m m m > > w .4 00 m m i co -4 -4 'o -o C < (D 0 M a i SUPERNATANT > m r! CD OUTLET (2) 4 m 0 20 RT.— 0 z > < M 2'!r rn I 14. z > io > 0 -4. 0 -4 0 rn > MISC OPOLYM-flq m STORAGE TANk > -4 AREA M m 1 v }r a Fi re I ME.TER BELT zc a FILT6,14 PRESS 1� rm a 0 WITH SLUDGE PUMP wm o 0 l z < < m 0 cc oo!�j m 0 100-1-9,11 0 0 z 0 0 m 0 -4 T m -4 0 0 0 0 0 a go m m > rl 0 0 m 0 0 < 0 > -4 m m m 0 z 0 0 > r !n 7 1 FT.3� -- — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — -- fit be enclosed in a building for odor control and weather protection for the equipment, supplies, operation personnel and chemical storage. This building has been conceptually sized to be approximately 26 feet x 16 feet which would provide sufficient floor area to accomodate the sludge feed pumps, polymer feed pumps, the belt filter press and a storage bin and conveyor for sludge cake discharge. Strong odors resulting from hydrogen sulfide (H2S) and mer- captan containing gases generated in this building from the unstablized liquid sludge would require careful management in order to prevent health, safety and aesthetic problems. For the operators' safety, approximately ten air changes per hour would be required. An activated carbon filter could effectively remove the H 2 S and mercaptans from the air. Carbon filters produce a waste liquid side stream when the carbon is regenerated. This wastewater will require treatment and disposal. The amount of time between carbon regeneration varies depending on usage time and the concentration of odor causing constitutents. If a 4 foot diameter carbon filter bed is utilized to filter air from the proposed building which has an assumed H 2 S concentration of 10 ppm, it would require regeneration about once every two years. The side stream wastewater from carbon regeneration has a high pH and may require chemical neutralization by addition of a low pH chemical before going to an STP for treatment and disposal. A storage tank would be provided for both the filtrate and washwater from the belt filter press and the wastewater supernatant from the grease separation tank. The total daily flow to this storage tank would average about 20,000 gallons. Due to this large quantity of wastewater, it would be desirable to locate the pretreatment and dewatering processes near a STP. The filter press cake would be transported to the County landfill for further processing. Only one trip per day would be required to transport the filter cake to the landfill site. At the landfill site, the dewatered sludge cake would be mixed with wood chips (or other carbonaceous material), and recycled compost material, and conveyed to the top of a bio-reactor vessel. Wood chips are used as a bulking agent. Chippers at Long Key and Cudjoe Key landfills presently produce wood chips from limbs and wood products disposed at the landfills. Data on the quantity 404A/AO6883 4-11 of wood chips that would be available on a daily basis at the County landfills is currently not available. The County should conduct a survey of the quantity of wood products received at the landfill that could be processed into wood chips and estimate the quantity of this material over the next 10-year period to determine if adequate quantities would be available to support this alter- native. Currently an average of 13.5 cubic yards per day of wood chips would be required to compost Monroe County's sludge (excluding GTPs). The oxygen level, temperature, moisture content, carbon to nitrogen ratio and retention time are controlled in the bio-reactor to optimize the controlled bilogical decomposition process called composting. Controlled composting generally requires about 12 to 14 days retention in the bio-reactor. Typi- cally, the biologically stablized product leaving the bio-reactor has a typical moisture content of about 60 percent, a carbon to nitrogen ratio of about 18 and requires curing. Curing would be accomplished by placing the material in covered static storage for 4 to 6 weeks. The final cured compost product would be biologically stabilized and should have no objectionable odors (i.e., it should have a musty odor similar to forest soil). Because it is a controlled, biological process, composting is subject to biological upset caused by toxic materials in the sludge. This should not be a significant problem in Monroe County since there are very few, if any, sources of heavy metals or other toxic containing sludges. The compost product can be used or disposed of in one or a combination of methods: (1) as a soil conditioner to improve moisture and nutrient holding capacity of native sandy soils; (2) mixed with the landfill cover to reduce its permeability and improve its ability to support vegetation; (3) coincin- erated with municipal solid waste at the County incinerator plants; and/or (4) directly landfilled. The site layout proposed for this alternative, as shown in Figure 4-4, encom- passes two -•tenths of an acre of land to accommodate this facility. There is approximately one-half acre at the Long Key Sanitary Landfill located adjacent to the existing incineration building which is currently unused and could be considered for siting this facility. Although the Key Largo Sanitary Landfill 404A/A06883 4-12 c m {--------------1 I COLLECTED BY HAULERS i I I } � 1�-4m co r A CH > j Mr, v� s d om o m I mm ��m 0*4rr° G) 0 1 TRANSPORTED MATER/ei a 1ca I >= » I -t I 0 rn (Ic7 I II c`",p c pokI r "O+ D "� I z C3 I "I r i Ir I I -+ m } a ,u � ►TANT m Q > �' ca - co °C v •p 0 r i i i } } i i } } } i i t } t } I I I fi I r I > I z x A I r GREASE D b 4 I m L__—_-----...._—......----------._--- > FIL TfATE i 0 0� oa Ir 4 � m toim a I O AA Q �d i7 M } I _� > n m c I c I I I. � i } t 1 } Site currently has a number of unused acres, the landfill design for the site provides; less than two -tenths of an acre which is not planned for landfill expansion. There is virtually no usable space remaining at the Cudjoe Key Sanitary Landfill Site. However, the County is currently negotiating to purchasing ten adjacent acres for expansion at this site. 4.6 ALTERNATIVE NO. 3 The Process Flow Diagram for this alternative in Figure 4-5 shows that this system would dewater unstablized liquid sludges, mix the dewatered sludge with wood chips and burn the composite mixture with municipal solid waste at the County incinerator plant. The "front end" receiving, storage and other unit processes through the dewatering operation would be identical to those des- cribed in 4.5 for Alternative No. 2. As with Alternative No. 2, large quanti- ties of "wastewater" would be produced from grease separation and mechanical dewatering operations, suggesting that the best location for the grease, grit and water removal system would be near a STP. Dewatered sludge cake from the filter belt press would be gravity dumped by the discharge conveyor from the press into a transportable storage bin (dumpster). Approximately 9.2 yd3 per day of sludge cake would be produced during the design year (1992). Therefore, a 9.5 yd3 roll -off container would be provided for cake storage/hauling. At the end of each day when all the daily sludge has been dewatered, a roll -off truck would pick up the container and trans -port it to the County incinerator plant where it would unload the cake into a hopper located adjacent to the incinerator building. The truck would then return the container to the dewatering site before the next day's operation.. The sludge cake hopper would gravity discharge onto a 13-inch wide screw conveyor which lifts the sludge cake to the top of a 19 ft. high active bottom storage bin. The screw conveyor is conceptually designed to be about 30 ft. long at a 40± incline with horizontal. When the sludge cake is delivered at the end of the day, the inclinded screw conveyor could transfer all of the dewatered sludge cake to be produced in the design year (1992) into the bin in about 15 minutes. 404A/A06883 4-14 K m > nr n Z m 0 > Z r> > > o m -� = C- p C m m m m n C $ -� z O M W r > 2 m m In o x m .... z r .,, 0 m 0 (A m m Z > A O z m m to v m 00 m z 0 r Z z 0v Z -- mn 0 Z 45 f C CA M m C O L L E C T E D B Y H A U R S L E C m > -4 m � I � 6� Ian J > j y CA QQ> I Zi m m 2 m m r c d I 6tJP /1TANT cc t- I m Z U > s 9 m Q I 'O r I � ., > ram- a M � s m ca � r O -� M > z m v > p 31 I -i I m m z i c m r= -+ ti o A m m ; -4 o m 0 > m ml a p _J > > m m F] T R A N 8 P O R T I I 7o� O O °D "� n o_I O v� o Z -a - O < m Z I n Z I m O m I cz, > m -� I I m > m o I I Z ICA r 1111 Z v m N r r v Wood chips could be pneumatically conveyed to the top of the active bottom bin by modifying the existing wood chipper at the County Landfill with an eleven foot chute. A cyclone separator would be installed at the discharge end of the chute to separate the wood chips from the air stream. Throughout the day, the wood chipping operation should be conducted next to the active bottom bin. Consequently, as the wood chips are being produced the existing blower would convey the chips up the chute and into the bin until it is full or the wood chip feed stock is exhausted. The active bottom bin would be equipped with 12 screw conveyors mounted in the bottom of the bin. A vertical partition would be installed in the bin, to segregate sludge cake from the wood chips. To provide the optimum 1 to 3.67 mix ratio between sludge cake and wood chips, the sludge compartment would have three screws in it's bottom while the wood chip compartment would have nine. The 12 screws in the bottom of the bin push the sludge cake and wood chips into a hopper (similar to a sloped bottom trough) which feeds a screw conve- yor. The sludge and wood chips mix at the hopper exit and continue to mix as they move through the screw conveyor to the incinerator. Live bottom bins work most efficiently when run on a continuous basis. How- ever, the incinerator is only charged once every five minutes with a charging cycle time of approximately one minute. The active bottom bin and screw conveyor would, therefore, operate for a total of approximately 2 hours per day in 1983 and for about 4 hours per day during a peak load in the design year 1992'. The screw conveyor would travel over the charging hopper and loop back to the active bottom bin in order to return the portion of wood chips and sludge that could not be incinerated (see Figure 4-6). The return loop will further mix the wood chips and sludge cake. On the bottom side of the con- veyor, a compartment with a trap door over the incinerator charging hopper will collect the sludge cake mixture as the screw travels over it. When the operator is charging the incinerator, he can push a button which would open the trap door and allow the sludge cake mixture to fall into the charging hopper. Assuming conceptual design dimensions of the compartment to be 7 ft. long, 1.1. ft. wide and 4 ft. deep; approximately 2 hours would be required to 404A/A06883 4-16 W k N W W O w a0 W w K my 0 �,.. zm Om ADZ r-- y m— Jnm M Otm CA) ! Z O nZ m x r... T -4 0> ,o as Z Z "� O Z m pnr Z> M -< 70 0 —1 C O Z A � i C m IV .► O m OD `� � iW a (a N :4 d it It 11 q 11 ❑. 1' 4 N N r Vim o 0 0 0 r o o 6 m vm ►' r< •c C a o 0 -1 0> n< ~ m In C o O 0 atn -- c m m :A o 0 0 0 pm -4 m r' o m m m o z r.0 m m-c ,T o v i > > r- _ >C -+ _n � O �� r. r r m t"4 > ,' r,. m X m 0 :0 o C)o < < m O mo m r a� m m m Z n 7D > 3L — m m CO cm m p W cn x v o v > a _ o O zy 0 -+ �' mz 0 M��m g > m :0 r = m tt - z m r C - > 0 rC 1 m z m a -� m >� x m m M co m -+ ti .. m co > r o o rn v m m'np C x-+> r ro o �' 0 O > m �C m 0 z > ..c C n > -+ > m G) -i 09 c .c m z O o > -+ z z a > 0 O z > 1 > co � X z ,10 r x > c � 0 0 o n m "v m C O m z C Z m m r M ra m z O Or- xn �m >Z m� >t3�p mz`1 >-MM Qx mz M- CGYC Mfaa MM10 � A O� �m .! -4z =mo -4L..b >m nx <r ca z b > N C) m>y p�M m* mmm 000 _COC mz r ob m> 2 -+"Z v�r o r, a > N �i w 0 O 42 FEET f FSLUDGE— — — ''RECEIVING AREA mo m n rn � a m >j 0 % < I > o N I m •v m N 'c: > pz ' i ca + CC J , Y o m CD z I m m _ ^4 61 m -4 r o z 00 :; Im -,m z m r Or Im w> O O >00 y I rz �0 M > z I '4 z r > .� 7D i z m m C n f -I i n 7C O > G) > C > M i m I > M > a m m > "1 L- J z z --- - - - - - V r z H 11 1, 11 11 a_ m z m r m m W � � C O O ; m > r m v C 0 0 z z m 0 0 z 57 FEET ± - ------- - - - - -� COVERED z c SLUDGE CAKE r- 0 I RECEIVING SIN > O w I M > ° >oo > >mm z G)>mm 0° I w�-+ °>o I� ° .Ao,n -40< O-+m 1=, 3) a °z '° <° ;<� oo mfl m l00 g0 •n >rn 1 a 0 Ic �0m m•sm r"loom 1m zM m� 14 mz I+� SLUOGE CAKE SIN I ' ° m Wo 0 C Fitt >x* I BIN M:iO I f �v son zo 0 4� c m m x 30-4 .c a a 2 o a a z z M m -4 o > O -4 G) m 0 O z v C 0 3 m m m r r m 0 m z 3 0 0 a to m charge all of the daily sludge cake mixture that would be produced for this system from the average sludge load in 1983. In 1992, 4 hours would be needed to change the increased mixture volume into the incinerator. Although this technique seems very promising for Monroe County, it should be approached on a highly experimental basis since there is very little, full- scale operating experience on the coincineration of mixed sludge and solid waste in modular controlled air incinerator units. A testing program should be conducted on a designated incinerator unit prior to implementing this alternative due to the potential for damaging the incinerator and possibly exceeding emission control limits. This alternative requires a minimal amount of land (0.1 acres near the STP and 0.08 acres at the landfill) for siting and has expectantly low capital and operating costs. Its primary disadvantage is that if sludge cake can not be coincinerated for any reason, the unstabilized sludge cake must be landfilled immediately to minimize severe odor problems and potential health hazards. 4.7 ALTERNATIVE NO. 4 Alternative No. 4 utilizes lime stabilization and mechanical dewatering to prepare the sludge for disposal via landfilling. Figure 4-7 shows the process flow diagram for this alternative, that would provide a stabilized, dewatered sludge with a 15 percent solids content which is acceptable for landfilling according to DER's current and proposed (17-7 Part IV FAC) regulations. Because lime is utilized for stabilization, a vacuum filter would be used for dewatering rather than a belt filter press. Vacuum filters have a relatively long history of dewatering sludge using lime as a conditioning agent. Lime is abrasive and exerts excessive wear to belts on a belt filter press. Equipment scaling is also a common problem when using lime. Although scaling can easily be removed with an occasional acid wash, it is difficult to remove lime scales from the large number of rollers and equipment parts involved in a belt filter press. Lime used for stabilization has the added advantage to this system in promoting better dewatering. Therefore, the polymer requirements for the vacuum filter are less than for the belt filter press. 404A/A06983 4-18 pR , Q w r m r WM ,irn► Z . *Sam arir V z Q m 0 Z :" 0 z. acre vow. > rn A primary benefit of this alternative is its small area requirements. Only about 0.1 acre is required for the equipment layout shown in Figure 4-8. The facility for grease separation, lime stabilization and sludge storage tanks would be identical to those identified in Alternative No. 1. A covered, self-cleaning screen would be utilized for this alternative rather than an in -line chopper. The screen would remove sharp objects like glass and metals that might damage the vacuum filter. Grit would not be removed in this alternative, because it increases the dewatering efficienty of the vacuum filter. Sand, lime granules and other grit accumulate on the vacuum filter and create a filtering matrix which helps capture smaller organic particles. As in the case of Alternative No. 2, the location for the stabilization and dewatering facilities should be at or adjacent to a STP, if possible. A roll -off container system like that described in Alternative No. 3 would be used to store and transport sludge cake to the landfill. At the landfill, sludge cake would either be mixed with the landfill cover or placed directly at the working face for codisposal with raw municipal solid waste and/or incineration plant residues. 4.8 REGULATORY REQUIREMENTS FDER is currently developing Part IV of Chapter 17-7 of the Florida Administrative Code (FAC) which classifies wastewater sludges and regulates their utilization and disposal criteria by classification. Although these regulations have not been finalized and adopted yet, the latest Predraft #9, dated January 11, 1983, gives a good indication of what the final rule is likely to include. Under the proposed sludge rules, all sludges are classified into one of three grades based on their chemical, physical and pathological characteristics. Mixed liquid sludges considered under this project would probably be classified as Grade III (the worst case) because of the variability of their composition. Grade III sludge can be disposed via landfilling. However, it must be dewatered to at least 15 percent solids prior to being landfilled. 404A/AO6983 4-20 r m w m Wow N Z o— Z < > m Z m 0 .� Z 3> OPFAMW r' r v> m -< o > C --1 —4 m Z M .0► r G m v A m D m D C m 0 v x 0 4 m O D n � D > > a m m m x m m Z n m m x Z ' a � Z -► c 0 O Z v O m Z > m 0 o O m -� _ m c v o C) 4 m to n 0 0 Z r a Z O n r m m o cn > v {o It it If n u 0 0 > Y v r m v < 4 � m c m n> a v -4 a 0 °r° z m o r m „C+,i r m -o v m r n C 70 W r m z > m CO o ov Z 0 z co 2 m ILM m C0 m > Z z r-° m c v 42 FT. --i O SLUDGE RECEIVING AREA m > m Im 0 c r AN m co ., v I a>s r; G o > Q m O a p m m I > z N rn 0 D z > m > m � z 1 -4 CA m -0 0 m O c< o > rn o m N 4 >©= m°° mm I mm o x40)zQ "I m > > r O o r z p Z > '4 m p 'O -4 O > IT! C� O c m� I > v m Z Q I c A c c 9 r- -+ m S r c v 0 m v c m m > z c > O O O r r r m I C O r c > O O is z O c c t -C p > m I m p Azi 7� > In >m > c 0 I z -4 m -4I > m > 2 � m m r > z Class I landfill criteria pursuant to Section 17-7.05 FAC must also be met. Each of the County's three sanitary landfills are being permitted as Class I Landfills and will, therefore, be able to accept dewatered sludge under these new rules as they are currently proposed. When the proposed sludge treatment facility begins handling more than 5,000 gallons of septage per working day, the treated product would need to be analyzed and classified annually according to proposed sludge rules. If sludge is coincinerated with municipal solid waste, applicable State rules on air pollution (Chapter 17-2 FAC) and water pollution (Chapter 17-3 FAG) apply as well as Chapter 17-7.09 FAC which addresses volume reduction plants. The Country's existing incinerators are currently permitted under these rules for solid waste disposal only. A pilot test program for conincinerating dewatered sludge and municipal solid waste in the County's existing incinerators should be conducted to determine whether these incinerators can comply with these rules. The FDER operating permits for the County's existing incinerators would require updating to include the incineration of sludge. Permitting requirements for sludge processing facilities in Monroe County will need to tie addressed further with DER to determine if the proposed system is considered to fall under domestic wastewater treatment in which the submittal of DER Application Form 17-1.122(2) may be required. By comparison, if the facility is considered a pretreatment facility there may be no FDER permit requirements. Owners of the STPs may require the filtrate to meet more strin- gent standards than the State regulations. 404A/AO6883 4-22 Section 5 CAPITAL AND OPERATING COST ESTIMATES Based on the conceptual design for the four alternative systems developed under Section 4, the capital and operating costs for each of these systems has been estimated and is discussed and evaluated in this Section. Operation and maintenance (0 & M) costs are based on average annual flow rates projected to occur during the design year (1992). Annual sludge flows were calculated by multiplying the average monthly figure shown in Table 2-3 by twelve. Tfie figures for 1983 were interpolated between 1982 and 1987. Table 5-1 summarizes the estimated 1983 capital and 0 & M costs for each alternative. These costs are itemized in Appendix A. Capital costs were amortized over twenty years at an annual compound interest rate of 10 percent. Replacement costs for component equipment with life expectancies of less than twenty years were factored into the 0 & M costs. The current (1983) electri- city and water rates for the Long Key area are estimated to be $0.069 per Kwh and $0.064 per 1,000 gallons, respectively. Since the location of the site is unknown at this time, the costs of purchas- ing land and transporting the sludge cake, and process byproducts such as grit, grease or supernatant have not been included in the cost estimates. These two costs can significantly affect the overall costs of each of the alternatives and their relative rankings. Therefore, land and transportation costs should be considered in the final cost estimates when a facility loca- tion has been sited. Table 5-2 projects the costs for each Alternative System through the year 1992, assuming a ten percent average annual inflation factor. Capital amorti- zation remains constant while operation and maintenance increases with time due to increased flow and the assumed ten percent inflation rate. Based on the economic projections in Tables 5-1 and 5-2, Alternative No. 4 is the most cost-effective alternative with an estimated annual cost in 1983 of 404/YO60883 5-1 d O O O O � r� N f� CT1 O W w w w .--I coO 00 �--� to Ln M CO Lo cli !f! 84 Q b4 Z OC W H J d M O O O CD LO O M N Ln O W w w _ w w Rd- 0 N 1-7 to �+ d d Ln O to 4 b4 Q b�4 Z W H J d W Q Z Or W F-- _J Q W Q Z OC' W Hi Q 404/Z060883 O O O O Ln LLi CO fM M w N to d d- cn O O N N m N .64 !s4 loc} O O O O O O O O 00 Ln M In 00 O w N 1w Nw Mw I-� O LO co M co .-+ <a4 b4 {f} J d O N M O O C ^ M O RS N CD w +� O C •r- CL' W •� +-� O a t6 m LL i N M •�- H- 00 'v +-) N m C i O •-4 � O U 0f QO LL- O +) to Z F U t0 + ) Z LN J i •r Q O U F- Q d eL7 J F- d C) U Q AWA r C C r r f0 4J b 4-1 to to cr, M CM N M LA U 1.0 00 Ln O a) 0 N d l0 0 O ct d C)N CD00 ra O O d co ^ O r-_ -4 m t0 S- +31 Cl m m O m +j O LO ^ cn r� a) •� rl rl rl N rl •r rl > = 64 = iO4 3= N O O O O O O O O a) r O O O O d r O O O O U W m i M to m m rO i G1 0o N O i �j 4-) w w w Ll) 4-) w w U �--� O\ N Ln CDN >.p\ 00 t0 N t0 a Q N M M M F- O d' Z W pC 'p F- r O O O O W r O O O O (1) J b O O O O H RS O O O O E Q +-) i. 00 00 co co J 4-3 S- n ^ f\ p •r- w w w w q •r w w w H CD.--N N N N a\ CD CD O O 0 r0 Al4 d d d -0-f0 kf M M M M m C..) N N N N U C O O O rr O O O O iO FCLO O O O i O O O O to � N .--r L1� Mtf\ww\nwww>- 64 C11 N 00 O O b4 00 t0 1 Ln a1 00 LO 0o d m p N N L- O W Q N 3 b (A b 0 Ir U r�-r 00 N N t\ u Ln co LP) M 4- LO F-• O O d O 1--4 O O n 00 N a) O W •r O ^ ^ C)1 rr r (D t0 ^ C11 rr r C r1 00 m rr O C r1 to r\ 01 00 4) H CD404 •r U Cl W rr W r m i + O O 00 w O O M w O O rr w O O rr w m W r co i +) O O LO O O d O O Cif O O to N a) 0 U r-•+ 1- i,4 M O t0 t0 p\ F- b4 w .--� w t0 N w CM � a) W H M LA O to O N r\ M S.. rr N rr H rr ri � rl U O Z � CC r Z r •r CL W ro i O O O O c rC i O O O O H +-) O O O O W +) O O O O +j J •r \ LO LO LA Ln - •r \ N N N N U Q aamr w n w w J co w w w Q) to N N N N Q •O U co 00 00 co U LL) LC) Ln V) i a 41 O O O O .--r O O O C)U �- OM C) C) i O CD C) CD a) 0CD 0 M N cm N r \ w w w k- O 64 rl Ln C; C; C) C)b? LO N 00 .4"rl N 00 i N 4J Q rn >- O O O O O O O O U a) \ O O O O O O O O +.+ to t0 O t0 1-1 t0 O to .--r to Lc; W M N M M M N CM M S= qJ LC) t0 w ^ w to w Ltd to rl to O O � rl rt rr rl w rl rl w rl rl U •r .L..) 4..t U a) r •--, Rs () a) O U O fT i N Q' M ^ N L. M n N L. CL a) Q 00 Oo 0*$ 0) 00 00 0*1 a) .� W >- Cn 01 cn > m cn m > rl r, . -L rt q '--r 404/DD060883 5-3 $88,900/yr. and in 1992, $172,200/yr. Alternative No. 3 ranks second in cost-effectiveness with a 1983 annual cost of $101,500/yr. and a 1992 annual cost of $172,900/yr. Alternative No. 1 ranked third and Alternative No. 2 with a significantly higher annual cost than the other alternatives was last The staffing plan for each of the alternatives shown in Table A-5 in Appendix A indicates the manpower estimated for each alternative. 404/Y060883 5-4 Section 6 FINAL ALTERNATIVES EVALUATION/RANKING 6.1 DESCRIPTION OF MATRIX EVALUATION SYSTEM The final evaluation of the four selected alternatives utilizes a weighted numerical matrix rating system. The following relative weights are assigned to the criteria listed below by assigning each a number between one and five with the number five representing the highest importance. Criteria Relative Weight Reliability 5 System Economics 4 Odor Control 4 Land Requirements 3 Flexibility 2 Each alternative system is then assigned an "alternative rating" from one to ten for each criteria to represent how well each alternative meets the cri- teria relative to the other alternatives. The "relative weight" is then multiplied by the "alternative rating" to produce a "weighted rating" for each alternative system. A discussion of the reasoning behind the "alternative ratings" assigned to each of the three alternatives follows in Section 6.2. The resulting matrix and ultimate alternative ranking is presented and dis- cussed in Section 6.3. 6.2 ASSIGNING "ALTERNATIVE RATINGS" TO ALTERNATIVES 6.2.1 Reliability The primary component of Alternative System No. 1 is the sand drying bed (SDB) for dewatering. The reliability of SDB's for dewatering is very good if the prior lime stabilization step is properly performed. The proposed manual addition of lime by the facility operator is, therefore, a potential factor for downtime or reduced reliability due to human error. Adverse weather is another factor that could slow down process time and efficiency and thereby affect 404/WO60883 6-1 reliability. The use of covers for the SDBs would substantially reduce the potential effects of adverse weather conditions on Alternative System No. 1. Other system equipment such as pumps, valving, and piping are expected to have minimal affects on system reliability. Since providing SDB covers signi- ficantly affects the assigned "alternative rating" (AR), this alternative is assigned one rating (AR=8) if covers are included and another rating (AR=5) if they are not. Alternative System No. 2 utilizes confined composting equipment for stabiliza- tion and a belt press to dewater the liquid sludge stream. It is a more sophisticated, higher technology system than System No. 1, which utilizes manual addition lime stabilization and SDB gravity dewatering. Consequently, there is a high potential for longer downtimes while repairs are made and/or special parts are obtained. The mechanical dewatering and conveyor systems used in this alternative are potentially high maintenance items. Scheduled downtime for belt replacement must also be factored into reliability con- siderations. Based on the above considerations for this alternative is assigned .an AR=6 for reliability. Alternative System No. 3, which utilizes mechanical dewatering and coincin- eration, in the County's existing modular controlled air incinerators is not considered a commercially proven alternative. Considerable downtime may be experienced during start-up if modifications to the original unit design are required as more is learned about coincinerating a mixture of dewatered sludge and wood chips with solid waste in a modular controlled -air incinerator. A relatively low reliability rating (AR=3) is, therefore, assigned to this Alternative System. Vacuum filters, the primary process component utilized by Alternative System No. 4, has a proven track record in numerous other installations for dewatering lime -stabilized sludge. Therefore, the reliability of this equipment is expected to be good. Increased confidence in the equipment selected to meet the required 15% solids content of Monroe County's sludge can also be expected 404/WO60883 6-2 as a result of the equipment testing program recommended prior to a final decision to purchase. Maintenance requirements for the vacuum filters are also expected to be low because these units are designed to utilize a minimum number of moving parts. The reliability of this System is, therefore, expected to be high and a relatively high reliability factor is assigned to it (AR=8). 6.2.2stem Economics The unit cost of each system is used to assign their relative alternative ratings (ARs) for system economics. The lowest unit cost is assigned the highest "AR factor". The unit costs determined in Section 5 are assigned the following "alternative ratings": Alternative System No. Unit Cost ($/1,000 gal.) AR Factor 1 101.17 3 2 197.63 1 3 81.23 7 4 76.04 8 6.2.3 Aesthetic Impacts The visual impacts of each Alternative System have potential for minimal or significant adverse impact on the surrounding environment depending on final system design, buffering and screening. Consequently, odors rather than visual impact are used for comparing aesthetic impacts of these alternatives. Alternative System No.'s 1 and 4 are controlled through lime stabilization prior to the dewatering process step. In comparision, in Alternative System No. 2 thE! stabilization step occurs in the bio-reactor after the sludge has been dewatered by a belt filter press. Although the exhaust air from this is filter press building is scrubbed to remove odors, odors from the dewatering press will be a problem to operational personnel in the belt filter press building. Alternative System No. 3 has some potential for significant odor problems during the transporting, handling and mixing of unstabilized sludge with wood 404/W060883 6-3 chips prior to coincineration since stabilization in this system is accom- plished after these steps during the incineration process. Comparing Alternative System No.'s 1 and 4, System No. 1 would be slightly more susceptable to odor problems than System No. 4 since the sand drying beds in System- No. 1 are exposed to the atmosphere while the vacuum filter press in System No. 4 is confined in a building and requires less time to accomplish the dewatering process. The following "alternative ratings" are assigned to each alternative based on the above discussions: Alternative System No. AR Factor 1 8 2 6 3 3 4 g 6.2.4 Land Requirements Since land is scarce and expensive in Monroe County, alternative systems which require less site acreage are assigned higher "alternative ratings." Although Alternative System No.'s 2 and 3 require the same 0.2 acres, the "alternative rating" assigned for System No. 2 is higher System No. 3, because the optimum site location for all facilities associated with System No. 2 is at the County landfill. The estimated land requirements and AR Factors assigned to the Alternative Systems are as follows: Land Alternative Requirement System No. (Acres) AR Factor 1 1.6 5 2 0.2 8 3 0.2 7 4 0.1 g 404/W060883 6-4 6.2.5 Flexibility Alternative System No.'s 2 and 3 are considered less flexible than Alternative System No.'s 1 and 4, because the belt filter press in Alternative System No.'s 2 and 3 requires adjustments when the solids content of the liquid sludge influent changes. The quantity of wood chips available for composting and coinc:ineration may also limit the flexibility of Alternative System No.'s 2 and 3. Since the use of covers over the sand drying beds in Alternative System No. 1 is considered to expand the range of solids it can efficiently dewater, and there are a multiple number of sand drying beds that are available for use, Alternative System No. 1 is considered more flexible than Alternative System No. 4. The "alternative ratings" for flexibility are assigned as follows: Alternative System No. AR Factor 1 8 2 4 3 4 4 6 6.3 EVALUATION RESULTS A summary of the results of the matrix rating system using the "alternative ratings" developed in Section 6.2 is shown in Table 6-1. Alternative System No. 4 is the top -ranked alternative by a relatively large margin while Alter- native System No. 1 finished second. Alternative System No.'s 2 and 3 finished third and fourth, respectively, with nearly the same scores. 404/W060883 6-5 d' 'Et: N N r % +� 3 M Mlp N r! I cr N I 00 O M 0) l0 Q Q M Cr- Ln 00 N .--4 00 Rd, � 3I ri cm e--I N I CO cr H CM 1� f'M 1-1 ei• Q CCI N W Q N 3I O N 00I N QOi M Z CC W F- CkCQ I t.o ,-4 tO CO -d- ,� J Q Q a) o Rs z z .--i 3 I CC d MLo .�-+ I C N X I CO (n CO Lr) 00 H Q Q Q W > F- J W W 3 w C� Z to Q (A • --) CL' v c E E W O r 0) �-- Oi +�� O •r C7 'r U d-) •r Q r W C CT r- W 3 E cam) C= - W r0 (D r J F- �- i•) Si X Q ]L to O C w f- Z Of O Z7 to r- O Q U w N CDJ lL 1- CL' 404/X061083 6-6 Section 7 FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS During the 12 month period beginning December 1, 1981, and ending November 30, 1982, Monroe County accepted an average of approximately 21,300 gallons of liquid sludge per month for disposal at the Cudjoe Key Sanitary Landfill and an average of approximately 104,800 gallons per month at the Long Key Sanitary Landfill. No liquid sludge was accepted at the Key Largo Sanitary Landfill during this period. The peak monthly quantity of sludge delivered to the Cudjoe Key and Long Key sites was approximately 29,300 gallons in February and 190,750 gallons in March, respectively. Estimates based on survey results indicate that the average percentage of each of the four types of sludge delivered to the landfills during this period are as follows: Sludge Type* Percent STP Sludge 28 Septage 51 PTPs 1 GTPs 20 Total Liquid Sludge 100 * See glossary for meaning of abbreviations. Based on population projections, it was also estimated that liquid sludge quantities can be expected to increase 7.4 percent by 1987 and 14.4 percent by 1992 over present quantities. The liquid sludge generated in Monroe County should be relatively "clean", that is, relatively free of contamination by heavy metals and other toxic compounds due to the absence of industrial discharge sources which typically generate "dirty" sludges. The STP sludge currently received by the County landfills is produced by either the contact stabilization or extended aeration wastewater treatment process and has been stablized by aerobic digestion. It 404/EE060883 7_1 should have a fairly consistent and predictable quality. By comparison, liquid septage sludge can be expected to have a highly variable degree of biological stabilization and solids/liquid content. Settling column analyses indicate that PTPs are about 5.5 times more concentrated than raw sewage. PTPs also normally contain significant quantities of rags and other debris, but very little grit. Because formaldehyde is added to PTPs for biological stablization to prevent septic conditions from occurring, further stabilization of PTPs is not necessary or practical. Formaldehyde is expected to cause problems in a combined biological treatment process with other liquid sludges, since it is diluted when mixed with other liquid sludge wastes to a concen- tration which is no longer toxic to bacteria. Therefore, biodegradation can occur. In general, the quantity and characteristics of liquid sludges pre- sently being disposed at the County landfills are highly variable and are expected to continue as such in the future. . In Section 3, it was determined that screening or grinding is a necessary pretreatment physical conditioning step for septage and PTPs to remove or reduce the large, coarse solids. Although grease in septage can be broken down using high doses of chlorine, there is a potential problem of producing chlorinated hydrocarbons which may be carcinogenic. The recommended method for grease removal is to allow grease to float to a water surface in a quies- cent tank:. Since the flow and strength of Monroe County's sludge stream is variable, flow equalization is needed. A grit removal system utilizing a quiescent tank is adequate for the small daily flows of septage expected in Monroe County and provides flow equalization. Gravity thickening is not recommended for Monroe County sludge, because of the poor settling characteristics of the older STP sludge, septage, and PTPs. Al- though centifuge thickening is feasible for Monroe County's sludge, clogging problems may occur if screening is not.adequate. Dissolved air flotation thickening is attractive if odors can be adequately controlled. Chlorine stabilization is not recommended because of the possibility of forming toxic chlorinated hydrocarbons. Stabilization through the use of a separate conventional biological treatment facility is not viable in Monroe County because of the small flow rates and the sensitivity of the system to varia- tions in the sludge characteristics. 404/EE060883 7-2 It was determined that three of the existing STPs in Monroe County were built large enough to accept metered septage and PTPs generated in the County into their liquid stream. However, because the Key Colony Beach STP is at capacity and the Landings of Largo STP is expected to have a flow too low to accept the septage and PTPs, only the Boca Chica STP could possibly be used to stabilize the liquid sludge stream. However, the Boca Chica STP has potential logistics problems. It is also not possible for the existing STPs in Monroe County to accept se!ptage and PTPs in their sludge (solids) stream because of the small capacity of their digesters. The addition of lime raises the pH and stabilizes any sludge regardless of its composition. Therefore, lime stabilization is recommended as a feasible process for Monroe County's variable sludge stream. A disinfection step is not considered necessary because either the potential viable sludge disposal methods do not require disinfection or some degree of disinfection is achieved by other more viable sludge treatment processes. Thermal conditioning is not recommended since the capital cost is extremely high for the small sludge quantities generated in Monroe County; the County incinerators do not recover energy, and it is expected that cake solids (15% by weight) can be produced without thermal conditioning. Elutriation is a conditioning process that requires an anaerobically digested sludge. It is, therefore, not considered a feasible process since anaerobic digestion is not practical for Monroe County's variable liquid sludge. The use of polymers and lime for chemical conditioning is considered the most viable conditioning op- tion, since it is adaptable to varying sludge conditions. When land is available at a reasonable cost, sand drying beds can be economi- cally attractive when compared to mechanical dewatering equipment. Sludge drying lagoons are not considered feasible in Monroe County because they would require large, dedicated land acreage and have a potential for creating envi- ronmental problems. Investigations reveal that heat drying processes are also not suited for Monroe County's small sludge stream because of the high cost, questionable reliability, and the prerequisite that sludge must be dewatered to a 20 percent solids content prior to heat drying. 404/EE060883 7-3 It was determined that high temperature processes should only be considered in conjunction with coincineration with solid waste in Monroe County's existing incinerator units to be economically viable. Wet air oxidation processes are considered uneconomical for the small quantities of sludge generated in Monroe County. Composting liquid sludge with solid waste may result in a product that would have an unstable market unless presorting of the solid waste is practiced. The high rainfall conditions make Monroe County more suitable for either a con- fined or a covered unconfined composting system rather than an uncovered unconfined system. Chemical fixation incapsulation and earthworm conversion technologies are considered impractical and/or uneconomical for processing Monroe County's liquid sludge stream. Although resource recovery is a potential future utilization option for Monroe County's sludge when it is coincinerated with solid waste, the only utiliza- tion considered viable presently is composting for public and/or municipal use (e.g., gardens, common lawns, golf courses, parks, etc.). Landfilling is considered a viable disposal option provided it meets the proposed state requirement of a solids content (by weight) of not less than 15 percent. Sludge management systems were developed in Section 4 to be compatible with landfilling as the ultimate disposal method. Incineration of sludge can reduce the volume and moisture content of the liquid sludge stream prior to landfilling. It is recommended that coincineration of dewatered sludge cake and solid waste be considered and evaluated based on test burns in one of the existing incinerator units. Another option to direct landfilling a stabilized sludge cake is to mix it with the landfill cover material. This would improve the impermeability of the cover material and may facilitate plant growth on the closed -out areas of the landfill. If the sludge is stabilized with lime, a small test area of the sludge cake and cover material mixture is recommended before a full-scale operation is implemented. This test area will help identify and solve poten- tial problems that may arise when the sludge begins to decompose, such as odors and a net loss of nitrogen which could prevent plant growth. 404/EE060883 7-4 It was determined in this report that GTPs should be delivered and treated separately from the other sludges to mitigate problems in the main process line. The GTPs can be simply and economically processed by allowing the grease and water to separate in a covered quiescent tank. Then, the water (supernatant) and grease can be pumped out separately. Concept plans were developed in Section 4 for the selected alternative system assuming a 1992 design (peak) flow of 10,000 gpd5 of liquid sludge without GTPs and 4,500 gpd5 of GTP flow. It is recommended that only one centrally located sludge processing facility be constructed initially because of the small flow of sludge in Monroe County. The following land requirements were determined from the concept plans devel- oped in Section 4: Alternative Land Requirement System No. Description Location 1 Lime stabilization and sand 1.6 acres adjacent drying beds (with or without to an existing STP. cover) 2 Mechanical dewatering and 0.2 acres at the composting County landfill. 3 Mechanical dewatering and 0.1 acres adjacent coincineration to an existing STP and 0.08 acres at the County landfill. 4 Lime stabilization and mechanical 0.1 acres adjacent dewatering to existing STP. The liquid sludge in Monroe County is expected to be classified as Grade III sludge under the proposed State rules which are to be issued in mid 1983. The proposed rules state that this sludge can be landfilled if it is first de - watered to 15 percent solids (by weight) and the landfill meets the Class I landfill criteria pursuant to Section 17-7.05 FAC. Monroe County landfills will be classified as Class I thus meeting this criteria. When the sludge processing facility begins handling more than 5,000 gpd, annual sludge analy- sis and classification are required. Chapters 17-2, 17-3, and 17-7.09 FAC must also be met if the sludge is coi nci nerated. 404/EE060883 7-5 Table 5-2 shows the present and future estimated operation and maintenance (0&M) costs, capital costs, and unit costs for the four alternative systems. The projected future costs increase because the O&M cost increases due to pro- jected sludge flow increases and an assumed 10 percent inflation rate. The amoritized capital costs remain constant over time. The alternatives ranked as follows in terms of the average unit cost over the 10 year period from 1983 through 1992 from the least costly to the most costly system: Alternative 1983 Unit Cost Rank System No. ($/1,000 gal.) 1st 4 76.04 2nd 3 81.23 3rd 1 101.17 4th 2 197.63 Land and transportation costs were not included in the cost evaluations. These two costs can significantly affect the overall costs of all the alterna- tive systems and at different proportions, therefore they may change the cost rankings. It is, therefore, recommended that the costs be reevaluated and refined once a site has been selected and approved. A weighted numerical matrix rating system was utilized in Section 6 to deter- mine an overall ranking of the four alternative systems in terms of the following criteria: Reliability System Economics Odor Control Land Requirements Flexibility 404/EEO60883 7-6 The overall alternatives ranking resulting from this matrix system analysis is as follows: Alternative Rank System No. 1st 4 2nd 1 3rd 2 4th 3 It is recommended that the County consider authorizing a site selection study to locate approximately 0.5 acre adjacent to a centrally located sewage treat- ment plant that is willing to accept washwater, filtrate and supernatant from the proposed facility. In 1992 the peak flow of the effluent (washwater, filtrate and supernatant) from the sludge treatment facility will be approximately 0.025 mgd. Figure 7-1 shows the location of 25 STPs that are currently hydraulically capable of accepting the sludge treatment facility effluent. The design capacity, aver- age flow and average excess capacity of each of the STPs shown in Figure 7-1 are given in Appendix B, Table B-1. The average excess capacity given in Table B-1. is the capacity available during the first quarter of 1983. The average excess capacity of most of the STPs is expected to decrease in future years as the area population grows. Therefore, the projected average and peak flows of the listed 25 STPs during 1992 should be investigated to determine which of the STPs will be hydraulically capable of processing the sludge fa- cility effluent at this future date. The impact on the performance of the listed 25 STPs from the BOD5 and total solids of the sludge facility effluent should also be evaluated. To help mitigate hydraulic, BOD5 and solids over- loading problems, the effluent from the sludge treatment facility could be stored in a tank and metered into the STP during its daily low flow period (typically between 3:00 a.m. and 7:00 a.m.). Simultaneous with the site selection study, physical and chemical analyses of representative samples of Monroe County's liquid sludge stream should be 404/EE060883 7-7 Z J O F- C < Z � O O O O N. } j IL Z W y Y W O Z m COO W J O J -J m �: } Z W J O le W z O Z -j O W ~ W cc m H _ W W Z LL LL 0 V aW W O t- O U: Q U -C z 0 $aHWQ 0278-0483A 7-8 W v Z O i co N O G t m W = =u N H ~ a z W W U � U -1 Q LL LL LL W O } W t —j J mCL U Q Q LL } z W J � J Q _U Q J W Q ~ MW c } C J a� U a co conducted. These sludge stream samples should also be tested through a number of different types of vacuum filters by the vendors to determine percent solids (by weight) attained in the sludge cake and the quantity and composi- tion of the filtrate. The results of these tests should be compared to per- formance specifications prepared by the Engineer. It is also recommended that Monroe County contact Mr. John Casski, Sewer Superintendent for the new Dade County South Sewage Treatment Plant which is expected to begin operations in March, 1983 at Black Point. Discussions with Mr. Casski should determine if Monroe County's sludge would be accepted for disposal at this facility and establish a sludge dumping fee. Then, once a sludge processing site has been selected and a purchase price estimated for the land, the total sludge processing/disposal cost for the selected alterna- tive system (including land purchase and transportation) can be determined and compared with the total cost of transporting Monroe County's sludge to the new Dade County South Sewage Treatment Plant and paying the established tipping fee. It is also recommended that Monroe County immediately reestablish the testing program conducted during this study to categorize the incoming sludge on a continuous basis. This additional data can be used for final design calcula- tions and can establish seasonal and annual trends in the composition of Monroe County's sludge. 404/EE060883 7-9 _APPENDIX A ITEMIZED COST ESTIMATES AND STAFFING PLANS Table A-1 ALTERNATIVE 1(1) ITEMIZED COST ESTIMATE CONSTRUCTION COST (2) 1983 $ 2 - In -line Choppers 16,000 4 - Sludge Pumps 15,700 2 - 4,500 gal. Grease Separation Tanks 18,200 6,000 gal. - Lime Stabilization Tank 6,000 2 - Conductivity Meters and 2 Water Level Detectors 2,000 10,000 gal. - Sludge Storage Tank 12,100 2 - Adjustable Submersible Mixers 4,000 Sand Drying Bed Construction (incl. installation) 116,000 Sand Drying Bed Cover 364,000 Small Front -End Loader 10,500 12' x 18' Lime Storage Shed 3,200 TOTAL Installation and Start-up @ 5%(4) _ Operating Cost Reserve (5) = Engineering, Legal & Administration @ 9% _ Contingency @ 10% = 56 800 $ 702,500 1983 Capital Cost = OPERATION AND MAINTENANCE Electricity Flat Rate Electricity Charge Sand Replacement Gas for Front -End Loader Labor Lime Disposal Air Vent Filter Maintenance and Repair of Items other than SDBs (19 of construction cost) TOTAL = Contingency @ 15% _ 1983 0&M Cost = (1) Lime stabilization and sand drying beds. (2) Includes freight cost. (3) Cost without sand drying bed cover. (4) Sand drying bed construction not included. (5) One month of operating cost. $ 567,700 22,600 4,300 51,100 14R1 P,/Ycar 200 200 3,800 500 27,000 8,200 200 4,500 $ 44,600 (203,700)(3) ( 4,400)(3) ( 4,000)(3) ( 18,300)(3) ( 20,400)(3) (257,900)(3) (900)(4) 6,700 $ 51,300/yr.(47,200/yr.)(4) NOTE: Transportation costs and land costs not included. 404/BB060883 A-1 Table A-2 ALTERNATIVE 2(1) ITEMIZED COST ESTIMATE CONSTRUCTION COST (2) 1983 $ 2 - In -line Chopper 16,000 Grit Removal Tank 7,200 10 inch Grit Classifier (with pumps) 19,500 4 Sludge Pumps 15,700 2 Grease Settling Tanks 18,200 2 Conductivity Meters and 2 Water Level Detectors 2,000 Sludge Storage Tank 12,100 Adjustable Sludge Mixer 2,500 Belt Filter Press (incl. installation) 115,500 16' x 26' Belt Filter Press Building 6,200 Air Filter for Belt Filter Press Building 21,400 Belt Filter Press and Grease Separate Supernatant Tank 12,100 Confined Composting Equipment & Accessories (incl. installation) 1,460,000 Roof for Curing Area (36' x 25') 11,700 TOTAL $1,720,100 Installation and Start-up @ 5%(3) = 7,200 Operating Cost Reserve (4) = 12,400 Engineering, Legal & Administration @ 9% = 154,800 Contingency @ 10% = 172,000 1983 Capital Cost = $2,066,500 OPERATION AND MAINTENANCE Belt Filter Press Electricity Polymer Belts Maintenance and Repair (1% of construction incl. building and air filter) Water Caustic and Activated Carbon for Air Filter Tanks Electricity Maintenance and Repair (A of construction) Disposal Air Vent Filters Composting: Electricity, Maintenance & Repair 404/BBO60883 1983 $/Year 200 4,700 1,200 1,400 100 1,500 200 1,000 200 2,300 A-2 OPERATION AND MAINTENANCE Labor Electricity Flat Rate Charge Table A-2 (continued) ALTERNATIVE 2(1) ITEMIZED COST ESTIMATE 1QQQ ct/v- 30,000 200 TOTAL = $43,000 Contingency @ 15% = 6,500 1983 0&M Cost = $49,500 (1) Mechanical dewatering and confined composting. (2) Includes freight cost. (3) Does not include belt filter press and confine composting equipment. (4) Three months of operating cost. NOTE: Transportation costs and land costs not included. 404/BB060883 A-3 Table A-3 ALTERNATIVE 30) ITEMIZED COST ESTIMATE CONSTRUCTION COST (2) 1983 $ 2 - In -line Chopper 16,000 3 - Sludge Pumps 15,700 10,000 gal. Grit Removal Tank 7,200 10 inch Grit Classifier (with pumps) 19,500 2 - 4,500 gal. Grease Settle Tanks 18,200 2 - Conductivity Meters and 2 Water Level Detectors 2,000 20,000 gal. - Sludge Storage Tank 12,100 Adjustable Submersible Mixer 2,300 Belt Filter Press (incl. installation) 115,500 17' x 25' Belt Filter Press Building 6,400 Air Filter for Belt Filter Press Building 21,400 9.5 yd. Sludge Cake Roll -off Container 6,200 Sludge Cake Hopper 2,300 Screw Conveyor (from sludge cake hopper to active bottom bin - incl. installation) 6,900 Screw Conveyor (loop between active bottom bin and incinerator - incl. installation) 13,800 11' Chute and Cyclone for Existing Wood Chipper 9300 Active Bottom Bin (incl. installation) 86,100 TOTAL $ 360,900 Installation and Start-up @ 5%(3) = 6,900 Operating Cost Reserve (4) = 12,300 Engineering, Legal & Administration @ 9% = 32,500 Contingency @ 10% = 36,100 1983 Capital Cost = $ 448,700 OPERATION AND MAINTENANCE Belt Filter Press Electricity Polymer Belts Maintenance and Repair (1% of construction incl. building, sludge cake container and air filter) Water Caustic and Activated Carbon for Air Filter Tanks, Pumps and Accessories Electricity Maintenance and Repair (1% of construction cost) Disposal Air Vent Filters 404/BB0601383 1983 $/Year 200 4,700 1,200 1,500 100 1,500 200 900 200 A-4 Table A-3 (continued) ALTERNATIVE 3(1) ITEMIZED COST ESTIMATE OPERATION AND MAINTENANCE Active Bottom Bin Electricity Maintenance and Repair (1% of construction cost) Screw Conveyor Electricity Maintenance and Repair (1% of construction cost) Electricity Flat Rate Charge Labor TOTAL = Contingency @ 15% _ 1983 0 & M Costs = (1) Mechanical dewatering and coincineration. (2) Includes freight cost. (3) Does not include the items previously noted. (4) Three months of operating cost. 1983 $/Year 500 1,000 500 200 200 30,000 $42,900 6,400 $49,300 NOTE: Transportation costs and land costs not included. 404/BBO60883 A-5 Table A-4 ALTERNATIVE 4(1) ITEMIZED COST ESTIMATE CONSTRUCTION COST (2) 1983 $ 20,000 gal. Sludge Lime Stabilization and Storage Tank 12,100 2 - 4,500 gal. Grease Separation Tanks 18 200 2 - Conductivity Meters and 2 Water Level Detectors 2,000 Self-cleaning Screen 11,000 4 Sludge Pumps 15,700 Adjustable Submersible Mixers 2,500 6' x 6' Vacuum Filter (incl. inst?43ation) 135,000 16' x 17' Vacuum Filter Building (3) 5,000 14 cu. yd. Sludge Cake Roll -off Contai 6,500 Air Filter for Vacu�r�)Filter Building 21,400 Sludge Cake Hopper 2,300 Screw Conveyor (from sludge cake hopper to to active botton bin - incl. installation) (4) 6,900 Screw Conveyor (loop between active bott?W)bin and incinerator - incl. installation) 13,800 11' Chute and Cyclone for Existing Woo �14C)hipper (4) 9,300 Active Bottom Bin (incl. installation) 86,100 TOTAL $ 204,300 (344,100)(4) Installation and Start-up @ 5% (5) = 3,500 ( 5,100) 6) Operating Cost Reserve = 14,500 ( 13,700) Engineering, Legal & Administration @ 9% = 18,400 ( 31,000)(4) Contingency @ 10% = 20,400 ( 34,400)(4) 1983 Capital Cost = $ 261,100 (428,300)(4) OPERATION AND MAINTENANCE(7) 1983 $/Year Vacuum Filter Electricity 1,900 (2,100)(4) Polymer Lime 3,500(854,700)(4) 8,200 Acid 4,000 Belt 200 Maintenance and Repair 1 500 Water ' 200 Caustic: and Activated Carbon for Air Filter (1,500)(4) Tanks, Pumps and Accessories Electricity 100 Maintenance and Repair (1% of construction cost) 600 Disposal Air Vent Filters 200 404/BB0608883 A-6 Table A-4 (continued) ALTERNATIVE 4(1) ITEMIZED COST ESTIMATE OPERATION AND MAINTENANCE Active Bottom Bin Electricity Maintenance and Repair Screw Conveyor and Sludge Cake Hopper Electricity Maintenance and Repair Electricity Flat Rate Charge Labor TOTAL = Contingency @ 15% _ 1983 0 & M Costs = 1983 $/Year (500)(4) (1,000)(4) (500)(4) (200)(4) 200 30,000 $50,600 (47,500)(4) 7,600 ( 7,100)(4) $58,200 (54,600)(4) (1) Lime stabilization and mechanical dewatering. (2) Includes freight cost. (3) Roll• -off truck required. (4) Cost estimate for coincineration when lime stabilization is bypassed. (5) Does not take a percentage of the items previously noted. (6) Three months of operating cost. (7) The line items with only one cost figure indicates that the cost is the same for lime stabilization and the bypass system. (8) Not required for bypass sytem. NOTE: Transportation costs and land costs not included. 404/BBO60883 A-7 N Z J d C7 LO Z LL- O ¢ -0 N - LU f- Z Of LU F- J Cc O OC: O O O O O CD O O a)O CDO O CD O O O O O ^ w w w CDQ Q t\N N CD O O ^ O 00 N N .-1 M I� �y iL O r- LJ I O e -� O r♦ O r-� . O S_ 4J 1� E_ _s � r 4 0 L i C L O 4-) ClJ 41 L CL eacli O O Q Z S_ a O CJ O O O N O 4 p Q 4i- O 2J N CDfn L O E V LE Co N li m Lto L m N r-4 L N M O ¢ CF O oIu M m m O CO O Li LL O I't A-8 APPENDIX B STPs HYDRAULICALLY CAPABLE OF ACCEPTING SLUDGE TREATMENT FACILITY EFFLUENT 404/SO60883 N cm Z f- H LZ Z W Lai C) = Li J d LL. 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C O i a) 3 Q) 2 rt +1 tv +) T7 > +J ' i m i O 3 +-> O a) i C r- �t a a) > 4-3 +� aJ i rt7 N Y C U >> t0 i� f= > +� C t6 C N _ U tC a) O Z J LN m 3 Y tN C!3 m H O Y O m Y tY d LLJ x -tt Lo LO 1\ pp m O rl N M d' LO to t\ M M CDrl ri rt . r-A .--t •- j rt r4 r! .--r N N B-1 N CD Z_ LL s� LtJ U..1 C-) =� U _J Q U_ u_ U_ UJ 0 W H- J �y Q �r d U 4L. `U- � F- J 2_ J UJ U - f-r aC J LAJ = Q F-- C] LtJ >- C 13 S Cl N _J N 404/Q042583 tN N O U7 LO M N N cz N N N N M: o 0 C)C7 X w o CD o C) CU C3) L N Q v 3 O r LL- o LO 1� M a) cz 0 0 C)O O) N: cc o 0 0 0 L CU Q 4J •r U N E Z LO o (D 0 M LO M M C) C) C) 0 0 0 0 0 CU U N L L O CU .a 4- E N M d m _= N N N N C O •r +•+ a3 CU O � CT i N O 3 +•+ o rn r r to 4- r +J rCf C O C O tm O E f0 •r C L i-) O N •r S- > 'r rtf •O > rt3 C � LLJ C 4J rt i 4- .r. o 4-j 0 4 •r N d F-- CU V) rQ rro a) L U E= tv 4-3 M. C rn (U M a o 0 'r F— +-) N N C •v am •r- = 4-3 L C ;..t C O a) N r CU4-O LL- 3 O r +-) 4- N N O 4- F- 0 N U N4-) C 4- •r CL) N O r U L •�- L d) O 4- N to O 4- 0 4- N . - +3 -0 C4-3 O C G) E N i-) +�4-) S- (o d) r0 TJ 0 4-) O •r C L o>> •3 4-J 4- 4-)N CV) M +-) 00 C L r- go C (A •r +-) UFO S- X +) O CU 3 m 0— d) — O Cn 4-)co 4-O N L Y L. L O (a > C) o LL Q d 4-) rr N co -::r LO %D r� 00 B-2 REFERENCES (1) Barnes, D. and F. Wilson. The Design and Operation of Small Sewage Works. London: E & F.N. Spon Ltd., 1976. (2) Metcalf & Eddy, Inc. Wastewater Engineering: Treatment, Disposal, Reuse, 2nd Edition. New York: McGraw-Hill Book Company, 1979. (3) USEPA. Septage Management. Office of Research and Development. Cin- cinnati, OH, 45268. EPA-600/8-80-032. August, 1980. (4) USEPA. Process Desiqn Manual for Sludge Treatment and Disposal. Office of Research and Development. Cincinnati, OH, 45268. EPA-625/1-79-011. Sept., 1979. (5) USEPA. Process Design Manual for Dewatering Municipal Wastewater Sludges. Office of Research and Development. Cincinnati, OH, 45268. EPA-625/ 1-82-014. Oct., 1982. 404/VO61083