Leachate treatment by recirculation within the landfill

Traditionally solid wastes generated in Puerto Rico have been disposed in sanitary landfills operated without any concern to the problem of groundwater contamination caused by leachate from landfills. Leachate contains high concentration of organic matter, heavy metals, and hazardous substances. It could result in pollution not only the groundwater, but sometimes the surface water as a nonpoint source. New federal regulation establishes that a leachate collection and treatment system should be provided in all new landfills in order to protect ground and surface waters.; Most of the wastewater treatment processes can be used for leachate treatment. However, the aerobic process for the reduction of high concentration of organics may be too expensive. Anaerobic process is a suitable approach for leachate treatment. Leachate treatment by recirculation within the landfill is a novel approach. This approach is attractive because it is simple and economical. Essentially, the landfill itself is used as a big anaerobic reactor for the treatment of the leachate.; The suitability of on-site leachate treatment by recirculation was examined in this work. A landfill located in the southwest Puerto Rico was used to evaluate this approach. Gas production, chemical oxygen demand (COD), and other parameters in leachate were monitored during various phases of leachate recirculation.; Results show that gas production increased after each recirculation phase, demonstrating an increase in microbial activity within the landfill. The recirculated leachate washed down the organics within the landfill causing an increase in the COD concentration in the leachate. However, it is believed that the COD in the leachate will be reduced as the recirculation process continues. This approach shows to be effective for leachate treatment, but more research is needed to determine the optimal recirculation flow and the duration needed to achieve the required pollutant reduction for final disposal.