Vertical flow wetlands and hybrid systems for the treatment of landfill leachate

Abstract

Landfill leachates contain a variety of toxic compounds, which makes them one of the most difficult types of wastewater to betreated. An alternative Bgreen^ technology for leachate treatment is the use of constructed wetlands (CWs). The aims of this studywere to select macrophytes and substrates to be used in vertical flow wetlands (VFWs) and to evaluate the performance of hybridsystems composed by a VFW and a horizontal subsurface flow (HSSW) or a free water surface flow (FWSW) wetlands for thetreatment of a high ammonium concentration landfill leachate. In microcosms scale experiments, Typha domingensis, Scirpuscalifornicus,andIris pseudacorus were studied to assess their tolerance to raw and diluted leachate. Substrate selection for VFWswas evaluated using different layers of light expanded clay aggregate (LECA), coarse sand, fine sand, and gravel. Contaminantremovals were higher in planted than in unplanted wetlands. Plants did not tolerate the raw effluent but showed a positive effecton plant growth when exposed to the diluted leachate. T. domingensis and I. pseudacorus showed higher contaminant removalability and tolerance to landfill leachate than S. californicus. VFW with LECA + coarse sand showed the best performance inremoval efficiencies. Hybrid system composed by VFW-FWSW planted with T. domingensis presented the best performance forthe treatment of landfill leachate with high concentrations of ammonium