PERFORMANCE AND INFLUENCING FACTORS OF VERTICAL HYBRID CONSTRUCTED WETLAND IN TREATING DOMESTIC SEWAGE

The efficient and low-cost distributed domestic sewage treatment technology has become one of the important factors restricting the construction of villages in China. Constructed wetlands (CWs) have been proved in the treatment of distributed domestic sewage. A pilot scale vertical hybrid constructed wetland (VHCW) with a small occupation area was designed and operated. Based on five years of continuous and stable operation (2018-2022), the influence of temperature, hydraulic load (HL) and hydraulic retention time (HRT) on removal efficiency of domestic sewage was studied. The concentrations of chemical oxygen demand (COD), total nitrogen (TN), ammonia nitrogen (NH3-N) and total phosphorus (TP) in influent and effluent were monitored in this work. The results showed that the average removal rates of COD, TN, NH3-N and TP in VHCW were 73.68%, 57.19%, 81.21% and 72.71%, respectively. The removal rates of COD, N and TP decreased with the increase of HL. The purification performance of VHCW does not change significantly with the temperature. HRT plays an important role on removal performance of VHCW and with the extension of HRT, the concentration of pollutants in the effluent decreased. However, excessive prolongation of HRT can also increase the concentration of pollutants in the effluent.