Challenge

The Zemel Road Municipal Solid Waste Landfill serving Charlotte County, FL, had to meet new state standards for deepwell injection of treated leachate and groundwater. Located in Punta Gorda, the landfill receives solid waste from throughout the county of about 125,000 population. Bentonite slurry walls direct the leachate into a French drain type collection system, then it is pumped to an on-site treatment plant.

To meet the new standards, the landfill needed a technology that could handle varying concentrations of contaminants, while fitting easily onto the site. Design contaminant levels were 1,000 milligrams per liter COD, 500 mg/l BOD, and 500 mg/l suspended solids.

Solution

To meet the stringent new requirements, Siemens Water Technologies supplied a batch-operated PACT system, which employs powdered activated carbon in conjunction with biological treatment, followed by a Hydro-Clear® fine sand filter.

The leachate and groundwater are pumped to an equalization storage tank, and then to a battery of three batch-operated PACT systems. The units are approximately 48 feet long by 12 feet wide and 12 feet high, each with a volume of 48,000 gallons. In batch operation, the leachate and groundwater are first mixed with powdered activated carbon and aerated in the activated sludge mode. This allows the system to metabolize and adsorb leachate contaminants.

Then the contents are allowed to settle, and the treated water is decanted and pumped to the Hydro-Clear filters. The filters remove remaining suspended solids. Finally, the water is chlorinated and injected via deepwell into a confined brackish aquifer, located approximately 2,700 feet below the surface.

Results

The system began operation in 1993, treating about 80,000 to 100,000 gallons a day. It has met the new requirements:

• Effluent COD less than 33 milligrams per liter
• Effluent BOD less than 6 mg/l
• Suspended solids less than 3 mg/l

 And it has been cost effective:

• Each batch unit completes a cycle once per day
• Operator attention is limited to one operator on a five day per week schedule
• Automatic operation can be achieved via a programmable logic controller
• Cost per gallon treated has been well in line with estimates