Leachate treatment options for closed landfills

Abstract

For many years up until the 1990’s uncontrolled disposal o f Municipal Solids Waste at various communal dumps occurred in Ireland. Since the establishment o f the Environmental Protection Agency and the implementation o f the European Union Landfill Directive these dumps have either been closed or regulated. This study sets out the legal and operational implications for local authorities to satisfactorily rehabilitate such disused landfill. Some local authorities have been left with a legacy o f rehabilitating such landfills. The landfill site at Muckish in Co. Donegal is an example o f one such site. It is a 2.6 ha site, which closed in 2001 with 56,000 tonnes o f disposed MSW. It is partially capped but has no containment system for leachate or any means o f treating this leachate. This study examines the various options available in Ireland, Europe or the United States o f America for the treatment o f such a leachate. Having established that the use o f constructed wetlands was a method successfully used to treat farm wastewaters in Ireland and also used to treat landfill leachates in Europe and the USA this study compares constructed wetlands against other options such as trucking the waste ofifsite to a wastewater treatment facility or the on-site treatment using a variety o f technologies. One such alternative on-site technology is a purpose built filtration system used to treat landfill leachate at another Donegal County Council landfill at Drumaboden. This system has shown a degree o f success in treating landfill leachate from this closed landfill and as such it became a basis o f comparison for constructed wetlands. While there are case studies that could be drawn upon to show the ability o f constructed wetlands to treat landfill leachate the US EPA have published cautionary comments as to the ability o f constructed wetlands to be successful in treating high strength effluents, particularly those which a high nitrogen levels such as encountered in landfill leachates. The conclusion to the study was that while ofT-site treatment is a solution the use o f a filtration system certainly is a viable alternative. The use o f a constructed wetland should be considered however, but its ability to be successful must be measured against the lack o f verifiable data to satisfactorily treat landfill leachate.