Treatment of landfill leachate by polyculture constructed wetlands planted with native plants

Abstract

 Use of constructed wetlands for wastewater treatment (domestic, storm water, landfill leachate, acid drainage mine) has increase since the mid 90´s. This paper presented the results of the study at pilot scale of constructed wetland (CW) for landfill leachate (LL) treatment planted with polycultures of tropical species Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He). The CW cells were operated during 7 months at continuous gravity flow (Q=0.5 m3 d-1). Three CWs were divided into three sections, and each section (5.98 m2) was seeded with 36 cuttings of each species. The other unit was planted randomly. The final distribution of plants in the CW cells was: CW-I (He- Ce-Gs), CW-II (randomly), CW-III (Ce-Gs-He) and CW-IV (Gs-He-Ce). All CW cells received pre-treated LL from a high-rate anaerobic pond (BLAAT®) operating as primary treatment. Influent and effluent from each CW cell were analysed for total and filtered COD weekly and heavy metal (HM) (Cd, Pb and Hg) fortnightly. Flowering, stem length, Chlorophyll and photosynthetic rates in plants were measured fortnightly. The removal efficiencies were good; with better performances in CW-IV (60-90%) for all parameters, indicating that plant distribution may affect the removal capacity of CW cells. All plants presented a good physiological response and constant growth along the research period. The native plants thus demonstrated their suitability for phytoremediation of LL and all could be categorized as HM accumulators.