Acute and sub-lethal toxicity of landfill leachate towards two macro-invertebrates assessing the remediation potential of constructed wetlands

摘要

Aspecific leachate that contained 1.036 mgl~(-1) of 2-chlorobiphenyl was used in the study (255 mgl~(-1) COD and 133 mgl~(-1) BOD_5).When operated on a 10 day hydraulic retention time (RT),reed beds planted with Juncus effusus removed 60% of the leachates COD,compared to 25% in unplanted beds.The constructed wetlands proved effective at reducing the level of acute toxicity to A.aquaticus and G.pulex.In untreated leachate,the LC_(50) for A.aquaticus was 57% v/v leachate in deionized water and 5% for G.pulex.When reed beds were operated on a 1-10 day RT,the LC_(50) for Asellus increased from 69% to below the LC_(50) threshold.The Gammarus LC_(50) also rose from 10% to 50%.The maximum toxicity reduction achieved by unplanted beds was 10% towards A.aquaticus and 5% for G.pulex,when operated on a 10 day RT.However,in sub-lethal concentrations of reed bed effluent (100%,80% and 60% dilutions,obtained from planted beds on a 10 day RT),the final length of Asellus was significantly reduced,in comparison to a deionized water control.It is also speculated that chronic leachate stress may have affected the fecundity of Gammarus,however,insufficient data was collected to statistically validate this hypothesis.