What is leachate?

Almost all municipalities have solid waste disposal facilities known as sanitary landfill sites. These sites are where residential garbage, organic waste and non-toxic materials are dumped. Whether closed or active, capped or uncapped, liquid from these dumped materials will percolate through the garbage mound, picking up more contaminants along its way. This contaminated liquid is known as “Leachate”, which eventually travels to the bottom of the landfill site and collected within perforated pipes. The collected leachate is then pumped to a treatment system or into a holding for disposal.

How is it treated?

Leachate contains a wide array of contaminants which can change over time with the age of a landfill as organics decompose and the availability of leachable material ls is lessened. As a result, the wide array of contaminants which can vary over time, makes leachate one of the most difficult wastewaters to treat. The first common step in any leachate is to filter out any particulate and insoluble materials. Next the waste stream is pH adjusted (if required) with the use of chemicals or electrocoagulation to remove colloidal and/or precipitates. After this step, the treatment approach can vary greatly depending on the remaining contaminants to be removed. Conventional treatment might use dissolved air floatation (DAF), SBR, MBR, clarifier, and other processes for final treatment. In some cases the leachate is simply collected and transported to a another facility for treatment such as a municipal wastewater treatment plant.

How can FO be applicable?

Forward osmosis (FO) has several advantages that can make it applicable to the treatment of landfill leachate. FO tolerates several contaminates that can be problematic for other treatment options and typically is less likely to foul due to the low applied pressure requirements. As such an FO leachate treatment plant has fewer treatment steps and less equipment than conventional treatment approaches.