Performance of constructed wetlands for the treatment of high strength organic effluents in northeastern Thailand

The objective of present study was to evaluate the removal efficiency of high strength organic wastewater using experiment scale of constructed wetlands by comparing the free water surface flow (FWS) and subsurface flow (SF) systems. The emergent plant employed was Cyperus sp. The average removal efficiencies for both systems were 57.8-61.4%, 79.9-86.8%, 88.6-92.0%, 46.9-58.1%, and 79.9-91.2% for BOD₅, COD, TKN, NO^-₃-N and TP, respectively. High removal efficiencies for both wetland systems were TKN and TP whereas NO₃-N removals were lower than other parameters. Mean removal efficiencies indicated that the SF systems were higher than the FWS constructed wetlands. Based on the t-test analysis, the average removal efficiencies of COD, TKN and TP for SF were significantly higher than FWS. In addition, relationships between BOD₅ removals and initial BOD₅ concentrations indicated a fairly significant linear relationship for the SF systems (R² = 0.59) and the FWS (R² = 0.54). Furthermore, COD removal were significantly influent by inflow COD concentrations as indicated by a strong significant linear relationship for SF (R² = 0.89) and FWS systems (R² = 0.90).