Treatment of landfill leachate in on-site lagoons and constructed wetlands

On-site “high-tech” leachate treatment systems are often avoided due to large construction and operation costs. Alternative integrated methods need to be examined. This paper describes a biological treatment system, capturing leachate from a municipal sanitary waste (MSW) landfill on-site. The area has a typical cool temperate continental climate. The treatment system is built in a ravine and has been operating since July 1993. The average flow is estimated to be 120 m3 d−1. The low-strength leachate is first treated in a 400 m3 anaerobic pond. Stage 2 is a 4000 m3 aerated lagoon with 3 AIRE-O2 aspirator propeller aerators/mixers. Oxidation of organic matter, NH4−N and Fe take place in this lagoon. Stage 3 is two parallel constructed wetlands (CWs) with horizontal subsurface flow, each with an area of 400 m2. The filters consist of (i) washed gravel and (ii) Light Expanded Clay Aggregates, LECA (size range 10–20 mm). The CWs were planted with Phragmites australis and Typha latifólia. Stage 4 is a 2000 m2 free water surface CW, planted with Scirpus and Typha. The integrated system has no moving parts, except for the aerators. The overall removal of organic matter, N, P, Fe and pathogenes is promising (70–95%). The paper presents combinations with the use of conventional and natural systems in MSW landfill leachate treatment.