Long-term performance of aerated and planted constructed wetland treatment on domestic wastewater

In this study, the course of BOD, TN, and TP removal in four stable operating lab-scale horizontal subsurface flow constructed wetlands (HSSF CWs) for domestic wastewater treatment was evaluated using a large pool of data from 7 years of operation. The aim of this study was to compare the impact of the different designs and the operational (planted and aeration or not) variables on the long-term treatment. The four devices used in the experiment, including aerated and planted CW (APCW), planted CW (PCW), aerated CW (ACW) and unaerated and unplanted CW(UCW), had the identical dimensions of 3 m in length, 0.7 m in width and 1 m in depth. Removal efficiencies of BOD and TN in APCW reached up to 94.4% and 86.0%. Also, BOD and TN removal of APCW varied little with the seasonal change, while that of PCW, ACW, and UCW had considerable fluctuation. Aeration had a significant influence on phosphorus removal in the long term, and plants could disrupt the structure of substrate to extend the time of absorption saturation. Correlation analysis showed that aeration and plants could accelerate CW to obtain a steady state either for BOD or TN removal. In the long run, we also found that removal rates of TN, TP, and organic matter were increased, decreased and almost constant, respectively.