Bio Solids Facility
Background
For many years, the Joint Meeting ocean disposed the sludge generated from its wastewater treatment process. This was a common practice for many New Jersey and New York treatment plants located along the coastal waterways stretching from Long Island to Cape May, NJ. Sludge was pumped onto barges which initially dumped the sludge 12 miles off the coast of New Jersey and, in later years, 106 miles off the coast. Ultimately, during the late 1980's, the ocean disposal of sewage sludge was banned by the USEPA and the N.J. Department of Environmental Protection. A Consent Decree issued by the USEPA to JMEUC required the development of a long-term sludge management plan utilizing beneficial reuse of sewage sludge.One of the options selected was to construct a sludge dewatering facility. Ultimately, a sludge incinerator would be constructed adjacent to, and shortly after the dewatering facility was operational. During this time, a temporary dewatering operation using belt filter presses was installed to dewater digested sludge. The cake was loaded into containers and trucked to landfills in eastern Pennsylvania. It was contemplated that this process would continue until the sludge incinerator was constructed and online.
However, the sludge incinerator project was abandoned due to public health concerns and a change in regulatory agency policies. Several alternatives to incineration were investigated by JMEUC's consultants. Ultimately, sludge drying technology was selected as the means to achieve compliance with EPA's long-term sludge management plan requirement.
The construction of the sludge drying facility (Facility) was completed during mid-1996; immediately following start-up, a series of demonstration tests were conducted in accordance with the contract specifications. The performance test results revealed numerous operating problems and failures to meet the requirements of the drying facility specifications. The most significant problem was the inability to produce a heat-dried pellet capable of being land applied as a fertilizer and with minimal dust generation. The failure of the performance tests led to several years of litigation and the drying facility was placed into long-term storage.
After several years of litigation, an agreement was reached between JMEUC and the manufacturer of the drying system who had also supplied the high pressure boilers and pelletization equipment. Modifications and additions to the originally supplied equipment were agreed to by both parties and with each party's responsibility clearly identified. The Facility was restarted following completion of the agreed upon system modifications. In addition to equipment modifications or additions, there were several modifications incorporated into the anaerobic digestion, sludge dewatering, and drying system standard operating procedures. Once again, demonstration tests were conducted for each drying train over a period of two weeks per train. This time the performance tests showed a significant improvement in the overall Facility operation. However, once again, a marketable heat-dried pellet could not be produced due to the tendency of the pellet to break apart into smaller particles during handling or land application and the generation of significant quantities of dust. Another phase of litigation commenced after the system modifications. All litigation was finally ended in early 2006. The drying facility has been mothballed since June 2004. The fate and future of the Facility remains undetermined at this time.
In order to comply with the Consent Decree requirements following the performance test failures and the commencement of litigation, the Joint Meeting, with the approval of USEPA and NJDEP, began using lime stabilization during late 1996 to comply with 40 CFR 503 regulations pertaining to Class B pathogen reduction and, also, vector attraction reduction requirements. These requirements regulate the beneficial reuse of sewage sludge as a fertilizer or soil conditioner via land application. The regulations require the addition of sufficient lime to the dewatered sludge to achieve an initial pH of at least 12.0 which is maintained for a minimum of two hours for Class B pathogen reduction. In addition, the pH must be maintained above 11.5 for 24 hours and without any further additions of lime to the biosolids for vector reduction. Since the implementation of the lime-stabilization process, JMEUC biosolids have been transported and applied to permitted agricultural sites, primarily located in Virginia. The land-filling of biosolids is no longer practiced by JMEUC unless it is used as an approved cover.
Overview of JMEUC Sludge Handling Process
Sludge generated by the primary and secondary wastewater treatment processes is thickened, anaerobically digested, dewatered, and lime-stabilized prior to removal from the plant site. Since 1998, JMEUC biosolids have been beneficially reused via land application at agricultural sites located in Virginia. The landfilling of sludge ceased as of March 1, 1998 in compliance with a USEPA Consent Decree which required the Joint Meeting to implement a "Long-Term Land-Based Management Plan" to beneficially reuse the sludge generated by the wastewater treatment process. Under the 503 regulations, the Joint Meeting facility is classified as "a preparer of sewage sludge". The anaerobic digestion process is not operated in a manner to achieve USEPA pathogen reduction or vector attraction reduction requirements. Those requirements are achieved via lime-stabilization which is described below.
Anaerobically digested sludge is dewatered to approximately 25 percent total solids via high solids, solid-bowl centrifuges. Polymer is added to the sludge immediately prior to the centrifuges to improve dewaterability and solids capture. The dewatering facility is normally operated five days per week (Monday through Friday) 24 hours per day. Occasionally, the facility may be operated six or seven days per week to reduce any solids backlog. Trucks are loaded with lime-stabilized cake throughout the day on an as needed basis.
Sludge Dewatering & Lime Stabilization Operation
Digested sludge at approximately 2.5 % total solids is pumped to the dewatering centrifuges by progressive cavity feed pumps. Polymer is added to the sludge immediately prior to the centrifuges; polymer is fed at an approximate dosage of 24 pounds per dry ton of sludge. Dewatered cake at approximately 25% total solids is conveyed to the onsite lime stabilization process prior to the truck loading area. The lime stabilization facilities consist of bulk lime storage and transfer equipment, day bins, volumetric lime feeders, and pug mill mixers.
Dewatered sludge cake is continuously fed to a pug mill mixer where high calcium granulated lime (minimum 90 - 92% available CaO) is added and mixed with the sludge cake. Lime is added from day bins via a variable speed volumetric feeder to maintain an initial pH greater than 12. The lime feed rate to the pug mill is automatically varied in proportion to the cake feed rate. The cake feed rate is determined by a weigh-belt conveyor immediately upstream of the pug mills. The lime feed rate and sludge feed rate are continuously monitored via a Programmable Logic Control (PLC) system and recorded hourly on shift log forms. After the pug mill, the lime-stabilized biosolids are conveyed to storage bunkers, which have sufficient capacity to store approximately one day of biosolids production. The original facility design included the installation of six twin cylinder, hydraulic reciprocating piston pumps to transfer the lime-stabilized biosolids from the storage bunkers to the truck loading station. The weight of each trailer load is recorded as wet tons and includes the weight of the dewatered biosolids plus the lime added for pathogen and vector control. Since there are no long-term on-site biosolids storage facilities at the Joint Meeting treatment plant site, trailers are normally removed from the plant site within eight hours after loading. The loaded trailers are transported to a nearby railroad terminal where they are loaded onto flatbed rail cars. The containers of biosolids are transported to a receiving terminal located in eastern Virginia.
JMEUC Biosolids Beneficial Reuse Program
Joint Meeting's contractor since 1998, Synagro, is responsible for coordinating all shipments of biosolids from the plant site to the permitted agricultural sites in Virginia. Synagro is also responsible for obtaining and complying with all permit conditions issued by the Virginia Department of Health. Synagro maintains records for each permitted site. These records include: the site latitude & longitude coordinates, proper owner data, type of crop, wet & dry tons of biosolids applied per acre, and the cumulative pounds of metals, nitrogen, phosphorus, and potassium applied per acre.
The JMEUC operations staff is responsible for conducting all onsite pH monitoring requirements in accordance with 40 CFR 503.
- PATHOGEN REDUCTION MONITORING - Class B Alternative 2 [40 CFR 503.32(b)(3)] - Lime Stabilization
- During normal operation, samples of lime-stabilized biosolids are collected immediately downstream of the pug mill mixer every four hours. These samples are analyzed for pH immediately after collection and two hours later to confirm the pH has remained at or above a value of 12. All sample results, including the date/time of collection, time of analysis, and analysts’ initials are recorded on pH monitoring log sheets which are kept on file for future reference. All pH measurements are corrected to 25oC.
- VECTOR ATTRACTION REDUCTION MONITORING - Alternative 6 [40 CFR 503.33(b)(6)] - Alkali Addition
- As noted above, samples of lime-stabilized biosolids are collected immediately downstream of the pug mill mixer once per shift to verify compliance with vector attraction reduction requirements. These samples are analyzed for pH immediately after collection to confirm an initial pH of 12 or higher. These same samples are retained for an additional 22 hours before the pH is measured again to confirm the final 24-hour pH is 11.5 or higher. All pH measurements are corrected to 25oC.
Dewatering Equipment Upgrades
The Joint Meeting (JM) has determined that the centrifuge DC backdrive motors are approaching obsolesce and will replace them with AC backdrives. The current upgrade is focused on the improvement of three (3) existing Alfa Laval DS706 dewatering centrifuges.
The Joint Meeting is also in the process of replacing the lime-stabilized biosolids truck loading reciprocating piston pumps. Since shortly after startup, these pumps have proven to be maintenance intensive. Aside from their high costs, JM has also experienced great difficulty in obtaining spare parts since the manufacturer is located in Germany and there are no parts distributors located in North America. At times, this has resulted in excessive loading times of the truck containers and a reduction in the centrifuge solids throughput. Ultimately, this has resulted periodically in increased solids inventories in both the wastewater and sludge processing trains. The long lead times to obtain replacement parts forced the JM to cannibalize out of service pumps to keep up with the treatment process sludge production rates.
In 20XX, a Moyno XXXXXX twin auger feed, progressive cavity pump was installed in the place of one existing piston pump. A performance trial was conducted for XXXX months to evaluate the performance of the pump. At the conclusion of the trial, the JM operations and maintenance staffs were satisfied with the pump's performance and purchased the pump. Currently, two more pumps have been ordered and received. A second pump began operating in early August, 2006. It is anticipated that the third Moyno pump will be installed by the end of the year. The remaining three original pumps will remain on standby. However, it is expected that the Moyno pumps installed will provide years of trouble-free operation and the three remaining piston pumps will be removed. The new Moyno pumps have sufficient capacity to meet the treatment plant sludge production rates; therefore, additional pump purchases are not planned for at this time.
Biosolids Facility Staffing
The Biosolids Facility dewatering and lime-stabilization process is typically operated 24 hours per day, five days per week. Periodically, the facility may be operated during weekends or holidays in response to increased solids inventory levels. The operations staff consists of a total of six operators; two operators are assigned per each eight hour shift. Additionally, a Shift Supervisor is assigned to the day shift Monday through Friday. The Supervisor is responsible for compiling all daily facility operating data and prepares the monthly facility operations reports. The main plant Shift Supervisor monitors the process during the first and third shifts, as well as weekend and holiday operating periods.
The Biosolids Facility is staffed with mechanical, electrical and site maintenance personnel Monday through Friday.. As conditions warrant, weekend maintenance projects are scheduled to be done while the process is shutdown.