Landfill Operations, Monitoring, and Maintenance – Leachate Treatment Plant, Confidential Client, California

SCS Engineers is providing operation, monitoring, and maintenance (OM&M) and engineering services for a Leachate Treatment Plant (LTP) located at a confidential landfill site in California.

Liquids treated at the LTP include leachate, groundwater and gas condensate from the Class I and Class III landfills and other site-process liquids, collectively referred to as “leachate.” The LTP is designed to treat 100,000 gallons per day (gpd) of equalized flow and currently treats an average of 50,000 gpd.

The system includes:

• Six influent equalization tanks with a total storage capacity of 120,000 gallons (greater than two days’ worth of storage). The purpose of the influent tanks is to provide adequate storage and blending of the incoming leachate sources so that the leachate flow and composition to the Powdered Activated Carbon Treatment (PACT) system is equalized.
• Two PACT reactors offering a total hydraulic residence time of 3 days at design flow achieving effective and complete treatment of the leachate constituents. The powdered activated carbon adsorbs toxicity found in the leachate and builds enriched bacteria colonies on the carbon surface to maintain a very high mixed liquor suspended solids (MLSS) concentration that is necessary to achieve the high removal efficiency and to produce high quality effluent,
• Two clarifiers separate the clarified effluent from the MLSS sludge. The treated MLSS flows by gravity from the PACT reactors to the clarifiers (operated in parallel or with one clarifier in operation and the other on stand-by) where treated liquid effluent is separated from the biophysical solids. The treated effluent flows from the clarifiers into the effluent storage tanks and is then pumped to a Million Gallon Reservoir for use in irrigation/dust control on the Class I landfill. Sludge which settles to the bottom of the clarifier is continuously pumped back to the PACT reactors as return activated sludge (RAS) or periodically pumped as waste activated sludge (WAS) to sludge storage tanks and subsequently dewatered in the filter presses.
• Accumulated filter cake is periodically transported to a permitted landfill for disposal.
• Other equipment includes two effluent storage tanks, two sludge storage tanks and two filter press units (for sludge dewatering).
• Routine and non-routine operations and maintenance services include daily monitoring of the process, process sampling, on-site laboratory analysis of untreated leachate, leachate being treated and the treated effluent, tank cleaning, chemical addition, pumping, sludge pressing, equipment maintenance and troubleshooting.
• Engineering and construction services conducted by SCS at the LTP include the design and installation of an inlet filtering system, design and installation of a programmable logic controller (PLC), refurbishment of the original clarifier, design and installation of a second clarifier, design and installation of an automatic chlorination system and the design and installation of various flow meters and level sensors.