Secondary Effluent Treatment by Pilot-Scale Constructed Wetland and the Character of Its Microbial Communities

A pilot-scale constructed wetland (CW) process was used as a backbone system to treat the secondary effluent and reuse them to supply the water body or irrigation instead of the clean water. This paper describes the design of the process as well as the operating results of the station. The design of the process emphasized efficiency, economy, simplicity, reliability, low construction cost and low land requirement. Autocontrol system ensured the operation of the process even without the technician. Turbidity, BOD₅, COD, SS, TN and TP of influent averaged at 45, 15, 61, 47.5, 30.5 and 1.65 mg/L, respectively. The final treated effluent´s Turbidity, BOD₅, COD, SS, TN and TP for the same period averaged 4, 5, 13.5, 6, 8 and 0.2 mg/L, respectively. In comparison with the Chinese national effluent standard (the reuse of urban recycling water - water quality standard for scenic environment use, GB/T 18921-2002) requirements for BOD₅, SS, TN and TP (6, 10, 15 and 0.5 mg/L, respectively), the results of the process demonstrate that the CW process is both effective and efficient in meeting the water discharge and reuse quality requirements. The molecular-based methods (PCR-DGGE) were used to analyze the microbial community structures of mixed liquor in the CW, which showed that the diversity of the microorganisms of the CW.