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HomeMy WebLinkAbout1979-08-21; City Council; 5973; Regional solids handling Encina facilityCITY OF CARLSBAD AGENDA BILL NO. _ ^T"f7^3 _ : _ Initial: Dept.Hd - 1979 _ C. Atty . DEPARTMENT: _ Public Works _ C. Mgr. '': C> /Q Subject: REGi0NAL SOLIDS HANDLING Eneina Water Pollution Control Facility Statement of the Matter • Discussion on making the Eneina Water Pollution Control Facility a regional solids handling facility; the impact of that new concept on the Phase III expansion and future expansions; instructions to Carlsbad's representatives to the Joint Advisory Committee regarding the handling of solids from the old Leucadia County Water District plant, proposed for reactivation (item placed on agenda at Vice Mayor Skotnicki's request). Exhibit Letter from Eneina General Manager dated August 10, 1979, Regional Sludge Treatment at Eneina Water Pollution Control Faci1ity. Council Action: 8-21-79 Council instructed their representatives to JAC to take a position regarding conversion of the Eneina Water Pollution Control Facility to a regional solids handling facility to agree to that conversion for the near term until the Phase III expansion has been completed provided that a suitable modification to the existing Joint Powers Basic Agreement is made to provide for equitable use of the facilities by all parties of the contract; that appropriate safeguards be provided to the City of Carlsbad as host city of the plant in the case of any satellite treatment plants that transfer solids for treatment to the Eneina Water Pollution Control Facility. * > ' . ^ ENCINA JOINT POWERS 6200 Avenida Encinas • Carlsbad, California 92008 Telephone (714) 438-3941 August 10, 1979 Vista Sanitation District City of Carlsbad Buena Sanitation District San Marcos County Water District Leucadia County Water District Encinitas Sanitary District Subj: Regional Sludge Treatment at the Encina Water Pollution Control Facility Enclosed is a copy of Brown and Caldwell's report concerning solids handling at the Encina Water Pollution Control Facility which are generated at upstream treatment plants. As directed by the Joint Advisory Committee, Roy Gann, Graham Fraser and I met August 9, 1979 to discuss preparation of a draft Supplement to the Basic Agree- ment or other agreement to permit discharge of solids from Leucadia County Water District's treatment plant and each other plants as may become operational in the future. Two items, which complicate development of an agreement, are the definition of sewage and the Basic Agreement with Supplements dealing with own- ership. Reasonable literature research did not reveal any definition of sewage which would specifically include or exclude solids from an upstream treatment plant. Thus, such solids could logically be considered as sewage within each agencies' right to send to the Encina Water Pollution Control Facility. The ownership of the Encina Water Pollution Control Facility is presently defined in the Agreement on basis of daily average volume of flow. Ownership has not been broken down to provide average daily flow, strength of sewage (solids con- tent and BOD ) and peak delivery flow rate. The Draft Financial Plan and Draft Revenue Plan, which are scheduled to be de- livered by Brown and Caldwell on August 11, 1979, will allocate costs based on flow and strength as required by CFR 35.929-la. These plans would logically provide a basis to develop a comprehensive agreement for solids handling on a regional concept. However, until the plans are approved by the State Water Re- sources Control Board and final cost estimates/bids obtained, a final agreement cannot be completely prepared. Subj : Regional SludgJ^freatment at the Enciha Water Pollutiore^ontrol Facility August 10, 1979 Page 2 In as much as it will be necessary for members of the JAC to agree upon quan- tities of solids, 8005, peak flow and cost ownership with operational costs by process step along with methods to adjust ownership/operational costs upon fu- ture changes in sewage, no interim agreement can be prepared. This will be in- cluded as an agenda item for discussion at the August 22, 1979 meeting of the JAC. Sincerely, R. F. Goodman General Manager RFG/mgt encl. cc: Roy H. Gann, Esq. Graham T. Fraser REGIONAL SLUDGE TREATMENT AT THE ENCINA WATER POLLUTION CONTROL FACILITY AUGUST, 1979 BROWN AND CALDWELL Pasadena, California REGIONAL SLUDGE TREATMENT AT THE ENCINA WATER POLLUTION CONTROL FACILITY The purpose of this report is to provide engineering input to the Agency's legal counsel to prepare a draft Supplement to the Basic Agreement to permit the discharge and subsequent processing and dis- posal of wastewater solids generated from upstream treatment plants within the Agency's regional boundaries. Background Information Project Report (Step I Report). A project report, prepared for the Enema Joint Powers Regional Sewerage Agency, entitled Phase III Enlargement and Upgrading of Encina Water Pollution Control Facilities dated February 1975, was prepared by Brown and Caldwell. This report recommended that the design be based on a BODs concentration of 200 mg/1 and a suspended solids concentration of 250 mg/1. The project report did not consider "satellite", or remote treatment plants with- in the Agency's service area nor their potential impacts on the Encina Phase III Expansion Project because the concept, at that time, was for complete centralization of wastewater treatment so that indivi- dual upstream plants could be abandoned. The project report was re- viewed and accepted by the State Water Resources Control Board (SWRCB). Phase III Ten Percent Design Report. The issue of the impact of "satellite" treatment plants on the Phase III project was not included in the scope of work for the preliminary design which culminated in the Phase III Ten percent Design Report. A proposal was made by Brown and Caldwell to the Encina Joint Powers Agency on December 28, 1978, to determine the impact of proposed "satellite" water reclamation fa- cilities on the Encina WPCF and to prepare an Agency-wide Sludge Manage- ment Plan. The proposal included a task to develop a coordinated Agency- wide "fail-safe" system to utilize the Encina WPCF's ocean outfall and to integrate this planning with an Agency-wide Sludge Management Plan. No action was taken on the proposal because of concerns by the JAC that the water reuse plans and the regional sludge processing concept for the Encina WPCF would affect grant eligibility for the Phase III pro- ject. The term "fail-safe" as used by members of the JAC and others implies that the system used for conveying treated effluent from "satellite" treatment plants to the ocean via the Encina ocean outfall is inherently safe and reliable. This is a misleading and false im- plication. Treated effluent from "satellite" treatment plants must be 2. conveyed by pipeline to the Encina WPCF and pipelines may become blocked or rupture. Also, after Phase III, the treated "satellite" effluent will, at times, need to be pumped through the outfall pipe- line by electric motor driven pumps which, at some time, may fail. For these reasons, Brown and Caldwell recommends the use of an alter- native term to "fail-safe" to describe these proposed systems. As a part of the Ten Percent Design report effort, Brown and Caldwell employed more recent data and re-evaluated the average waste- water strengths to be used for the Phase III design. A BODs concen- tration of 230 mg/1 and a suspended solids concentration of 235 mg/1 were recommended in the Ten Percent Report and these values have been accepted by the SWRCB for the purpose of determining project eligi- bility. "Satellite" Treatment Plants. In recent years, a number of treatment plants have been proposed in the project planning area. The term "satellite" plant infers some dependency on a regional facil- ity. However, this term is commonly used regardless of such a depen- dency. Satellite treatment plants may be dependent upon a regional plant for the following: • Treatment and disposal of solids removed from the wastewater. • Treatment of wastewater volumes in excess of the quantity of reclaimed wastewater needed. • To pump and discharge through the - ocean outfall treated reclaimed wastewater when such reclaimed wastewater cannot otherwise be utilized. Satellite treatment plants provide the following advantages: • Providing all reject flows bypass the central facility, additional treatment capacity for the project planning area can be obtained. • Because approximately 50 percent of the capital and operating costs are associated with sludge treatment and disposal, and because peaking flows need not be considered, satellite plants can be economically con- structed and operated. The satellite wastewater treatment facilities therefore may be somewhat smaller than a plant designed for variations in wastewater flows. • Satellite plants can be located near the point of demand for reclaimed water, resulting in reduction of reclaimed water transportation costs. • Elimination of adverse impacts on plant neighbors from sludge treatment and disposal. c o Regional Solids Processing - Pros and Cons Regional solids processing at the Encina WPCF and a central ultimate disposal system for wastewater solids from the region is attractive for a number of reasons: • Capital costs for a single large wastewater solids treatment facility to serve the region will be less than the cost of constructing a number of smaller solids processing facilities plus a facility at the Encina WPCF of only relatively slightly reduced size. • Operating costs for a single large wastewater solids treatment facility will be much less. • Energy can be recovered from the sludges at the Encina WPCF because of equipment and facilities to be provided under Phase III. This energy could not economically be recovered at the smaller upstream treatment plants. • A large regional plant will more than likely be better equipped and operated than smaller upstream facilities and will be manned 24 hours per day, 7 days per week. Hence, the potential for mishaps which could cause odors are considerably less likely to occur at the regional plant compared to a smaller upstream facility. The potential disadvantages include the following: • Poor primary sedimentation tank performance when wastewater temperatures become high during the summer. Poor performance may be caused by anaero- bic conditions causing gassing to occur in the sludge as it is transported to the treatment plant in the sewers. The gas bubbles will cause the sludge to float rather than settle in the primary sedimentation tanks. • Reduction in primary sludge concentrations if large quantities of activated sludge are pumped from the satellite facilities. Even a reduction of one-half percent from 5% to 4-*s% concentration will increase the primary sludge volume by 10 percent. • Some solubilization could occur in the sewerage system as the solids are being transported to the regional plant. This will increase the BODs load to the plant causing an increase in the operating costs for treating the BODs in the wastewater as well as for the additional secondary sludge that is produced that must be thickened, digested, dewatered, E) • Deposition of sludge solids in parts of the tributary sewerage system. These solids deposits could cause local odor complaints if decomposition occurs. Also, sections of the sewerage system could be damaged by sulfuric acid attack as a result of anaerobic decom- position of the sludge deposits. • During a rainstorm after a dry period, sludge which has accumulated in the sewerage system will be flushed into the treatment plant, causing an abrupt stress on all sludge processing facilities. Such a sudden stress could affect the proper operation of the anaerobic digestion system. A monitoring program is not listed as a pro or a con because such a program is required implicitly by Federal Regulation CFR 35.929- l(a) "User charge system based on actual use" as the basis of each user paying a proportionate share of operation and maintenance costs. Such a program must be based on each user's proportionate contribution to the total wastewater loading. The regulation requires this loading be based on factors such as strength, volume and delivery flowrate characteristics. Preliminary Concepts Domestic wastewaters contain two main pollutants: suspended solids (SS) and biochemical oxygen demand CBOD). Approximately 65 percent of the suspended solids are removed in primary treatment. Approximately 35 percent of the BOD is removed with the solids in primary sedimentation. The sludge removed in primary sedimentation is called primary sludge. Primary sludge thickens more effectively than secondary sludge and is easier to dewater. The remainder of the suspended solids and the BOD pass to the secondary treatment facilities, where the BOD is converted into sec- ondary solids. These solids are then settled out in secondary sedi- mentation tanks, thickened, digested with the primary sludge, dewatered then hauled to landfill for ultimate disposal. Since BOD is converted into solids in the secondary facilities, it can be seen that when wastewater is being treated to secondary standards, more solids than were actually contained within the waste- water in the first place must be removed. This concept is an important one because if one mgd of domestic wastewater is treated at the Encina WPCF, approximately 1,270 pounds of solids will be removed in the pri- mary sedimentation tanks. If the same million gallons per day is treated in an upstream secondary facility and all of the sludge is 'pumped to the Encina WPCF, approximately 2,000 pounds of primary and secondary solids would be removed in primary sedimentation. Projected Wastewater Volume and Sludge Quantities The following table assumes that the construction of satellite treatment plants for San Marcos, Buena, Carlsbad and Leucadia will ./•s 5. generate an additional 5.57 million gallons per day of wastewater and 7,510 pounds of sludge within the Agency's regional boundaries by the year 1990. (Data provided by C.M. Engineering Associates). The table assumes that this additional capacity will be approved by the C.P.O. and by the Regional Water Quality Control Board. This quantity is in addition to the 26 mgd of wastewater and 52,500 pounds of sludge pro- jected in the Project Report for the year 1990 to be tributary to the Encina WPCF. Whether this additional growth will actually occur is a matter for considerable conjecture. Alternatively, if the wastewater volume (population) projections for the area within the Agency's bound- aries remain relatively consistent with the projections in the project report, the impact of these satellite treatment plants on the Encina WPCF will be to reduce the average wastewater flow to 20.43 mgd. If all of the sludge from these satellite plants is discharged to the Encina WPCF, there will be no change in the overall sludge quantity projected for the 26 mgd flowrate. Sludge Quantities - 1990 - 26a mgd Plant Flow Primary Sludge gallons/day Secondary Sludge gallons/day Without Satellite Plants Satellite Plants Totals 79,450b 18,000<*,e 97,450 78,OOQC Of 78,000 aProject report projection; assumes no reduction of wastewater volume ,at the Encina WPCF as a consequence of satellite treatment plants. Assumes 5% solids concentration of 33,000 pounds per day. GAssumes 3% solids concentration after thickening of 19,500 pounds per ,day. Assumes all of the 7,510 pounds of sludge projected by C.M. Engineer- ing in a letter to the JAC on May 11, 1979, settles in the primary sedimentation tanks and the overall concentration of primary sludge remains at 5%. Of the 7,510 pounds, 4,640 pounds are projected to be primary solids; 1,770 pounds fixed media solids; and, 1,100 pounds activated sludge solids. eAssumes satellite treatment plant sludge is a result of additional .-population increase in the Agency's service area. Assumes that the sludge yield remains constant, BODs does not increase as a result of solubilization of discharged solids into the waste- water as they are transported to the treatment plant and that all satellite solids are collected in the primary sedimentation tanks. The foregoing quantities of sludge, due to the proposed satellite plants, should be considered to be a minimum until monitoring can deter- mine the actual impacts. For example, not all of the satellite plant sludge may be recaptured in the primary tanks. Also, solubilization or decomposition of the sludge may occur in the transport sewers to the treatment plant, changing the sludge quantities and characteristics. 6. Impact on the Encina WPCF The sludge quantities from the satellite plants projected by C.M. Engineering Associates fro the year 1990 should be capable of being processed at the Encina WPCF without adverse impact providing the facilities at the Encina WPCF are designed and constructed in sufficient time to process the additional sludge quantities. The plant also must be designed to accommodate the increase in hydraulic and solids loading from 18 mgd, as designed for Phase III to 26 mgd (or 20.43 mgd) projected for the year 1990. In the intervening years, however, care should be taken that the additional solids loading does not overload the Phase III or other intermediate design capacities. The impact on the Phase III project will depe~nd on how soon the satellite plants are placed into operation and their total loadings compared to the loadings otherwise tributary to the Encina WPCF. Without any satellite treatment plants being placed in operation, the hydraulic flow into the Encina WPCF is expected to reach design capacity of 18 mgd by 1983; or, in other words, at the end of the equipment commissioning period for the Phase III Project. With satel- lite treatment plants, the hydraulic design flow of 18 mgd may not be reached until a year or so later but solids processing capability will be reached earlier than 1983. It is prudent, therefore, under Phase III,' to design those elements of the solids processing systems which cannot be incrementally expanded to present projections for ultimate needs and to design all other ele- ments to facilitate future incremental additions. Accordingly the Design Review Committee, on June 27, 1979, authorized Brown and Caldwell to increase the diameter of the new digester currently under design for the Phase III Project from 95 feet diameter to 105 feet. All other solids related facilities are to be designed for relatively convenient modular expansion and in ac- cordance with previously agreed upon parameters. It should be recognized, however, that additional operational costs will be incurred because of additional running time of the equipment and for additional chemical costs. Financial Allocations The Financial Plan currently being prepared by Brown and Caldwell for the Phase III Project will recommend that the local share of the capital costs for the Phase III Upgrading and Expansion Project be allocated between the member agencies in accordance with the following three wastewater characteristics: 1. Annual wastewater volume (millions of gallons) 2. Annual pounds of suspended solids Cthousands of pounds) 3. Annual pounds of 6005 Cthousands of pounds) 7. Allocation factors representing each of these parameters are being developed to divide the cost of the new facilities (approximately $40,000,000) into three parts: that attributable to wastewater volume; that attributable to suspended solids; and, that attributable to BOD5. From these costs, the total of the local share of the new construction costs attributable to these three parameters will be determined. The allocation of this total local share between the six-member agencies will be based on the volume of wastewater plus the suspended solids and BODs from each agency. Upgrading and expansion are being treated separately because there is a different ownership allocation between the six agencies for the upgrading compared to the expansion. The Revenue Program is being prepared in a similar manner. The cost of the first year of operation is being divided into the three parameters of wastewater volume, suspended solids and BODs. This cost will then be disaggregated to each of the six Agencies in accordance with the wastewater volumes, suspended solids and BODs fr°m each of the Agencies. The Financial Plan and Revenue Program is being prepared for the Phase III Upgrading and Expansion Project on the basis of 18 mgd and an average suspended solids of 235 mg/1 and an average BODs of 23° from each of the six Agencies. The wastewater strengths from each of the Agencies will vary from these values. Each Agency will pay in accordance with the volume and strength CSS and BODs) discharged to the Encina WPCF for treatment. If the Encina Joint Powers Agency wish to permit discharge of additional wastewater volumes, suspended solids or BODs quantities to the Encina plant which differ from the values currently projected for the Phase III expansion Cwithout satellite plants); the a process similar to that described above for the Phase III Financial Plan and Revenue Program must be performed for each incremental increase in unit loadings to re-allocate the cost of capital expansions and O&M costs. Treatment capacity should be thought of in terms of all three parameters; volume, suspended solids and BODs. A portion of the cost of the solids processing systems will be allocated so suspended solids (primary sludge) and a portion to BODs (waste activated sludge). If the quantity of either suspended solids or BODs are increased, there will be a corresponding increase in the costs of the solids processing systems. Cost Sharing Agreement Between Agencies Based on an analysis of cost sharing agreements developed by Brown and Caldwell for other regional systems, the following check list of topics to be included could be helpful in developing a supple- ment to the Basic Agreement: • Objectives of Agreement • Definitions 8. Right to service — rights of the agencies responsibilities of JAC ownership of facilities responsibilities of the agencies for capital-related annual costs responsibilities of the agencies for operation and maintenance costs Permitted rates of service wastewater flowrates and mass emission rates capacity for each agency - exceeding permitted flowrates and mass emission rates transferring capacity shares between agencies participation of future parties at a later time Wastewater quality effluent to meet regulatory agency standards - mutual right of inspection influent quality restrictions - influent sampling and analysis Operation, maintenance and replacement costs responsibilities metering and sampling future facility requirements and agency responsibilities operation, maintenance and replacement costs extraordinary costs - payment - records inspection user charge/industrial cost recovery system Capital-related costs - method of apportionment of capital-related costs - update of capital cost apportionment procedure for cost sharing for future facilities Modification of this Agreement Records and accounts Insurance Manner of giving notice Arbitration Term of Agreement 9. • Time of essence • War and other contingencies • Severability • Effective date of Agreement Recommendations and Conclusions • Encina WPCF can be designed and operated to serve as a regional sludge processing facility for upstream satellite water reclamation facilities. __ • Phase III design should be changed to increase the diameter of the new (4th) digester from 95 feet to 105 feet to ac- commodate the additional sludge solids that may be discharged to the plant by 1983. No other changes or additions are recommended at this time for the Phase III project. • Additional Operating and Maintenance (O&M) costs will be incurred as a result of additional satellite plant sludge. • A supplemental Step I Report should begin in the near future so that construction of additional wastewater and wastewater solids processing facilities may begin as soon as the Phase III construction work is completed. This schedule will be necessary to assure that the Encina facility has the addi- tional capacity required for waste volumes and loads pro- jected for the mid-1980's. This capacity includes capacity for treating the suspended solids and BODs loads from satel- lite reclamation facilities. This supplemental Step I Report may be performed under the orginal Step I grant for the 1975 Project Report. • A supplement to the Basic Agreement should be developed using the principle that each of the six Agencies will share in all costs in accordance with beneficial use. We recommend that these costs include capital costs for the Phase III Up- grading and Expansion Project, O&M costs and for any addition- al capital and O&M cost associated with loadings from any of the Agencies in excess of their allocated capacity. • Allocated capacity should be developed for each Agency in terms of the following parameters: a) Wastewater volume (millions of gallons) b) Suspended solids (thousands of pounds) c) BOD5 (thousands of pounds) • Each Agency should implement a monitoring program to measure suspended solids and BOD$ in addition to wastewater volume discharged to the Encina WPCF. Capacity allocations should 10. be based on these measurements. The monitoring program should be continuous and managed by the Encina Joint Powers Agency. • Whenever an increment of treatment capacity, in excess of that owned, is requested by a member Agency, a capital and O&M cost allocation analysis should be conducted and the applicant advised of the additional cost to be incurred as a result of the requested additional incremental capacity. • An O&M cost allocation analysis, based on three parameters: Wastewater Volume, Suspended Solids and BODs, should be performed annually to determine each Agency's fair share of the O&M costs. • Sewers should be designed to ensure sufficiently high transport velocities to convey previously settled sludge to the Encina WPCF without accumulating in the trunk sewers. • The tributary sewerage system into which sludge from satel- lite treatment facilities is discharged should be regularly inspected to insure that sludge is not settling in parts of the system. If sludge deposits are found, additional flushing water should be discharged with the sludge to prevent deposition. The inspection program should be managed by the Encina Joint Powers Agency and the Agency should have the power to direct the offending Agency to flush out the sewer and to thereafter prevent future accumulations from oc- curring. This could be accomplished by adding more liquid to the sludge to raise the transport velocities or to implement a regular sewer flushing program.