A survey on experiences in leachate treatment: Common practices, differences worldwide and future perspectives

The necessity for landfill leachate treatment is a requisite to reduce the environmental impact related to municipal solid waste landfills and different aspects must be considered while deciding for an appropriate treatment process. For example, it was demonstrated that the landfill leachate stabilization in tropical regions is achieved right after its first year of operation, requiring technologies capable of treating leachates of a higher recalcitrant character if compared to those leachates from temperate regions and same landfill age. In view of its complexity and variability, stand-alone processes (either biological or physicochemical) are often ineffective in attaining the threshold values for its discharge in receiving bodies. Due to that fact, full-scale facilities have adopted integrated routes, harvesting the benefits of both biological and physicochemical processes. The implementation of membrane bioreactors followed by polishing membrane separation process (nanofiltration and reverse osmosis) seems to be a trend in leachate treatment by full-scale treatment plants. This technology is widely employed in China, European countries, and tropical countries as Brazil, generally with a treatment cost lower than the costs related to its disposal in domestic effluent collection systems. From the technologies already employed by full-scale facilities, four integrated routes were proposed for a sensitive analysis considering the treatment of a landfill leachate of different physicochemical characteristics. From all routes, those employing the membrane separation process as a polishing step had a better efficacy in attaining the threshold values for leachate disposal, being that an interesting alternative for leachate polishing by full-scale facilities.