Study on ABR Stage-Constructed Wetland Integrated System in Treatment of Rural Sewage

Prompted by the constructed wetland without long-term stable operation and anaerobic baffled reactor (ABR) with higher suspended solid (SS) removal rate, a full-scale ABR-constructed wetland integrated sewage treatment system was designed and applied to treat low strength rural sewage in Yunnan, China. All the trials lasted 36 months, and the results of trial indicated that SS removal rate of the ABR stage and the integrated system was over 75% and 86% at 23°C. When the temperature decreased to 13°C, the SS removal rates of ABR stage could maintain 65.26%. The hydraulic retention times (HRTs) of anaerobic digestion tank, anaerobic contact tank, surface flow constructed wetland and underflow constructed wetland were set as HRT1, HRT2, HRT3 and HRT4, respectively. At 20-25°C, under the condition that HRT1=61 h, HRT2=49 h, HRT3=7 h and HRT4=7 h, the COD, TN, TP removal rates of integrated wastewater treatment system could be over 81.19%, 82.33% and 67.25%, respectively. Based on the results of trial, the extending the constructed wetland's operational life was evaluated, and the mechanisms of higher efficacy and long-term stable operation of integrative sewage treatment system in treatment of low strength rural sewage were owed to high efficient SS removal rate at ABR stage.