Effectiveness of constructed wetlands in reducing acute toxicity of reclaimed water

HE Shunneng; WU Wenyong; HAN Yuguo; HU Yaqi; MA Meng; JIANG Tingting

doi:10.13522/j.cnki.ggps.2024291

Abstract：[Objective]Constructed wetlands are an effective technology for wastewater treatment.This study experimentally investigates their effectiveness in reducing the acute toxicity of reclaimed water.[Method]The experiment was conducted in two wetlands,one in Niantan and the other in Annan.In both wetlands,the acute toxicity of reclaimed water was evaluated using the luminescent bacteria assay.The effectiveness of the constructed wetlands was assessed by measuring the equivalent concentration of the toxic reference substance zinc sulfate heptahydrate(ZnSO·7H2O).[Result]Subsurface-flow wetland was found to be more effective than subsurface-flow wetland,particularly in reducing the acute toxicity of reclaimed water.The subsurface-flow wetland in Niantan reduced toxicity levels by 16.16%,and decreased the average luminescence inhibition rate by 19.31%.The subsurface-flow wetland in Annan reduced the inhibition rate by 18.55%,with a final effluent inhibition rate of 10.64%,representing a 9.39%reduction compared to the influent.In the Niantan system,the equivalent concentrations of ZnSO·7H2O in the influent,surface-flow wetland,and effluent were 0.930,0.553,and 0.466 mg/L,respectively,while in the Annan system,the concentration of ZnSO·7H2O in reclaimed water,wetland effluent,surface-flow wetland effluent,and final outlet were 0.535,0.109,0.277,and 0.262 mg/L,respectively.After treatment,the reclaimed water quality remained within safe thresholds,with acute toxicity levels considerably low.[Conclusion]Constructed wetlands effectively reduce the acute toxicity of reclaimed water,with subsurface-flow wetlands demonstrating superior performance compared to surface-flow systems.