Treatment wetlands for landfill leachates - case studies from Norway

Abstract

The paper describes operational experiences of landfill leachate treatment systems at threeNorwegian landfill sites, with emphasis on the reduction of COD, nitrogen and Feconcentrations. The leachate systems described consist of aerated lagoons with aspiratorpropeller aerators/mixers, and horizontal subsurface flow treatment wetlands. Results ofleachate monitoring and treatment efficiencies are presented. Operational data show thatleachate treatment with aerated lagoons has problems with removal of organic matter andnitrogen, but remove Fe. Failure seems to depend on high loads (especially in winter times),sludge erosion and toxicity. The hydraulic retention time should to be >20 days to keep thenitrifiers in the lagoon during periods with low temperatures. Simple filtration techniqueswith e.g. bark, shell or coral sand, crushed concrete and others can improve leachate qualityboth during and after other treatment stages and remove nitrogen, colour, heavy metals,organic pollutants and pesticides, and buffer pH and add other nutrients. A combination ofaeration, dams and filtering techniques probably gives the best treatment options.