A pre-production-scale investigation was accomplished to the combined “anaerobic digestion-anoxia-aerobic-constructed wetland”system.The mechanism of anaerobic filters was investigated through the tracer study and mass balance calculation,the CODCr removal efficiencies of anaerobic filter was analyzed, and the effect of hydraulic retention time (HRT) on the efficiency and operational characteristics of the large height-diameter ratio anaerobic filter reactor were evaluated.The results revealed that the anaerobic reactor started successfully after 65 days at medium-low temperature.During the stable running period,when the hydraulic retention time (HRT) was 72 h,the removal rate of COD(Cr) was remained about 37.8%.The combined process which consisted of aerobic digestion-anoxic regulation-waterfall aeration contact oxidation-vegetated constructed wetland to deal with decentralized domestic sewage could achieve good removal effect,the average concentration of the effluent were 39.3 mg/L,the average removal rate in turn were 86.2%,which reached the class A emission standard in the“urban sewage treatment plant pollutant discharge standard”(GB18918—2002).
