Leachate is created when water percolates through decomposing household waste. Collecting and treating the leachate is an important component of making the landfill safe. Once the landfill is capped the quantity of leachate diminishes because the amount of water that comes in contact with waste is minimized.
The goal of the leachate collection and treatment system is to prevent leachate from entering the environment surrounding the Freshkills Park site. Leachate is currently collected on site in a series of pipes installed around the perimeter of each mound. Once in the pipes, the leachate is transported to an on-site Leachate Treatment Plant which has the capacity to treat up to 600,000 gallons of leachate per day. Because the landfill cap has prevented new rainwater from entering the landfill, the Treatment Plant is now treating less than 100,000 gallons per day.
The plant uses physical, chemical, and biological processes to breakdown the leachate. This produces clean water and a material called sludge. The treated water is cleaner than the nearby Arthur Kill into which it is discharged. The sludge also has a lot of water in it, which is removed at the plant, producing sludge cakes. The dry cakes are then shipped to a landfill facility in Pennsylvania.