[Effect of DO distribution on contaminated urban stream water treatment performance in constructed wetland]

We evaluated the effect of dissolved oxygen (DO) on the performance of two pilot-scale constructed wetlands in treating contaminated water from an urban stream. The aim of this study was to investigate a more effective DO distribution in contaminated stream water treatment wetland that may aid future constructed wetland design effort. The results show poor natural aeration condition and inadequate DO in wetland directly result in the deterioration of effluent water quality. Natural waterfall is an effective aeration way and can improve DO concentration in wetland. The aeration capability of waterfall can be evaluated by oxygen deficit ratio (the ratio of difference between concentration of saturated DO and DO measured before and after waterfall). The distributions of DO obviously correlated with the quantity distribution of micrdorganism and removal rate of organic contaminants in wetland, however there was no obvious relationship between DO and TP removal rate. Results of the study also indicate setting multi-waterfall in plug-flow wetland can balance the distribution of DO and improve the nitrification.