Effect of feeding rate and frequency on organics and nitrogen removal in VFCWs with a novel reoxygenation corridor

摘要

Subsurface oxygen transfer rate is considered one of the main rate-limiting factors for removal of organic and nitrogenous compounds in subsurface flow wetlands used for domestic wastewater treatment. In this paper, a novel reoxygenation corridor was set up in vertical flow subsurface constructed wetlands (VFCWs) to improve the subsurface oxygen transfer and pollutants removal. The experiment results indicated that the existence of corridor can improve the internal oxygen environment of VFCWs and the removal efficiency of chemical oxygen demand (COD) and ammonium nitrogen (NH4+-N). The feeding rate experiment results showed that the best removal of COD, NH 4 +-N and total nitrogen (TN) were 89.6%, 71.0% and 57.4%, respectively. Moreover, in feeding frequency experiments, the best removal efficiency of COD, NH4+-N and TN were 86.9%, and 77.8% and 58.4%, respectively. Finally, the 180 L/h feeding rate and 12 times/d feeding frequency were selected as optimal operation conditions. These findings can give useful guidance for the design and operation of VFCWs with a reoxygenation corridor.