Effect of hydraulic loading rate on the removal efficiency in a constructed wetland in subtropical China

This study evaluated the effect of hydraulic loading rate (HLR) on the removal of water pollutants with an integrated vertical flow constructed wetland in subtropical China. There were three plant species in the constructed wetland, Coix lacryma-jobi and Canna edulis in warm seasons and Lolium perenne in cold seasons. The percentage removal of ammonium (NH4-N), total phosphate JP), chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) all showed a shallowly negative response to an increase in HLR from 200 to 1200 L m(-2) d(-1), while the mass removal rate showed a markedly positive response to HLR. The upper limit for mass loading rates of NH4-N, TP and BOD5 did not occur, even when HLR was increased to 1200 L m(-2) d(-1), while the equivalent for COD occurred when HLR reached 1000 L m(-2) d(-1). It is concluded that the design of this constructed wetland was very efficient in removing aqueous pollutants.