Contact us Learn more about our complete range of services.

PACKAGED SYSTEM TREATS LANDFILL LEACHATE WILLIAM C. BALDWIN and NORBERT H. ELLIS Leachate treatment is one of the most difficult issues the solid waste industry faces. It is a high profile and complex problem that attracts government and the public's interest like few others. The word "leachate" has many undesirable connotations. However, the solid waste industry has faced this issue head on, and in the process, significantly contributed to the body of knowledge that will permit future environmental safeguards. Solutions have steadily moved from the drawing board through the successful implementation of on-site hardware in a remarkably short time. A case in point is the Boyertown Sanitary Landfill located near Gilbertsville, Montgomery County, PA, owned by NSWMA members Warren K. Frame and Michael P. Miller. The Boyertown Landfill was one of the first landfills in the country to implement leachate collection. In addition to collection, the owners wanted to solve leachate disposal successfully using state of the art technology at their 100 acre facility. The Problem Stormwater from rainfall permeated the uncapped site, percolated through the fill and became contaminated. The resulting leachate which was routinely discharged directly to the municipal sewer system became a problem due to increased concentrations of organics. The presence of organics was attributed to both municipal and industrial waste. Additionally, the landfill had been granted interim status as a hazardous waste site. As the landfill expanded, a sophisticated dendritic type leachate collection system was designed and implemented. This system complimented an earlier system which consisted only of perimeter trenches and a collection pond. However, the Boyertown Landfill management displayed a progressive nature by treating leachate through a contact aeration step followed by settling. These steps preceded discharge into the local sewer network. With the advent of tighter regulatory control, and since very little was known about leachate composition, the raw leachate was sampled and analyzed by AGES Laboratories, Valley Forge, PA in accordance with EPA guidelines. Analysis by gas chromatography and flame ionization detection techniques yielded a breakdown of the individual chemical components and their respective concentrations. The raw leachate was profiled for a period of 18 months. Test results identified the waste as a combination of organics ranging in volume from barely detectable to 6000 ppb. However, the waste profile was extremely beneficial in the determination of an appropriate treatment scheme. The design of the treatment system was primarily directed towards removal of organics such as methylene chloride, dichloroethylene, toluene, phenols, and benzene. Although metals, total dissolved solids, and total suspended solids were present in the leachate their removal was of secondary concern and not the focus of the treatment plant design . The Solution In order to effectively treat the leachate, a physical/chemical treatment system, preceded by a biological step, was designed by AGES Corporation to reduce the concentration of organics by 85 percent. The treatment phases include the following: Flow equalization, Aeration and biological reduction of raw leachate by use of a fixed film reactor, Clarification, Filtration, Flash mixing and pH adjustment, Ammonia and volatile organic stripping, pH neutralization, and Organics removal by carbon adsorption. The system design incorporated the use of an existing contact aeration tank, converting it to a fixed film reactor. In addition, an existing clarifier was upgraded with baffles and a weir box. Leachate from the landfill is collected in a 250,000 gal leachate storage/equalization lagoon. The lagoon is double lined with a 50 mil chlorinated polyethylene primary liner over a 20 mil PVC liner. A leak detection system is located between the two liners. Waste is introduced by controlled gravity flow from the raw leachate storage lagoon to the bottom of the fixed film reactor (submerged trickling filter). This reactor is aerated utilizing existing aeration facilities. The reactor was constructed by supporting biological media atop a coated iron grating. The media in combination with the aeration significantly reduces TOC levels. Effluent from the fixed film reactor flows by gravity into a baffled clarifier over a broad crest weir on the common wall of these two concrete tanks. A sump outfitted with level control float switches receives supernatant from the clarifier. The level control allows a sump pump to send the waste to the next treatment phase. The pump transfers the leachate through a 100 micron cartridge filter to the first stage pH adjustment tank. The filter micron cartridge filters remove suspended particles. Each filter has an average life of 80 hours before replacement. Flash mixing and adjustment to pH 10.5 in the first stage pH adjustment tank require a retention time of at least 60 seconds. A high speed mixer assures complete contact of the pH adjustment chemicals (sodium hydroxide) with the leachate to aid in the subsequent removal of ammonia by stripping. The chemical dosage is controlled by the influent flow rate and can be manually adjusted as required without interrupting process flow. A centrifugal transfer pump draws leachate from the first stage pH adjustment tank and transfers it to an air stripping tower for the removal of ammonia and/or volatile organics. The stripping tower has a 15 ft deep packed bed and operates at a minimum 10: 1 (air to water) ratio. Following the stripping phase, a second stage pH adjustment tank is used to readjust the pH of the leachate. Acid is added by a metering pump until the pH is lowered to 7. Another centrifugal pump then routes the neutralized leachate from the second stage pH adjustment tank to two air-fluidized, upflow, granular carbon adsorption columns which are piped in series. The columns use a bituminous coal-based activated carbon with high surface area to remove any remaining organic contaminants. Each column measures 8 ft in height by 4 ft in diameter with an actual carbon bed depth of 4 ft. The carbon adsorption columns, first and second stage pH adjustment tanks, cartridge filters, pumps and controls were all skid mounted by the Met-Pro Corporation of Harleysville, PA. The package was prewired and prepiped to facilitate transport and to provide a quick and inexpensive installation. The system was designed for unattended operation; operators need only check makeup chemical levels and equipment daily. A small 1,000 gal pump station receives effluent from the carbon columns and transfers it to one of two 100,000 gal effluent storage basins. Construction materials for the effluent basins are a 30 mil Hypalon primary liner over a 20 mil PVC secondary liner. A leachate detection system is located between the liners. The treated leachate is sampled and analyzed to insure the treatment has been performing up to specification. When the analysis of the sampled effluent basin indicates that the treated leachate is safe and acceptable, the effluent is then discharged to the sewer by a variable speed pump. A rotating intrusion type flow meter monitors liquid volume before discharge to the local sewer network. The inexpensive flow metering unit provides accuracy to within plus or minus 1 percent and repeatability of plus or minus 0.5 percent. The Results The system has run continuously with little maintenance or operator attention since August of 1985. The system was specifically designed to remove organic contaminants so that the effluent could be discharged to the local water course. However, the Pennsylvania Department of Environmental Resources decided not to set effluent limitations for this stream and instead has required a discharge to the sewer. Testing and laboratory analysis of the treated effluent confirm the effectiveness of the system. In concentrations up to 1,000 ppb, all organic contaminants were removed with an overall system removal efficiency of 100 percent. All organics were removed to non-detectable levels for nine months as measured at the discharge of the carbon adsorption columns.