Purification Of Rural Domestic Sewage With High COD And NH₄⁺-N Through Aerobic/anaerobic Series Artificial Wetland

In recent years, with the rapid development of China’s new rural construction,sewage emissions showed a gradual growth trend, and highlighted the characteristicsof high COD, NH₄⁺-N. And generated sewage are usually far away from themunicipal sewage pipe network,so untreated sewage mostly directly discharged intothe aquatic environment, and cause water pollutions in rural areas. According to theproduce and discharged characteristics of sewage in China’s rural, especially the northcountryside. It needs to establish a set of efficient low consumption and easilymanaged sewage water purification technology which meets the characteristics of thecharacteristics of northern rural domestic sewage.The research was built in Longkou North Town, Qingdao, China. In view of thesewage with characteristics of high COD, NH₄⁺-N and the actual situation of LongkouNorth Town. According to previous results of laboratory simulation test, we use anae-robic baffle reactor （ABR）-biological contact oxidation （BCO） andaerobic/anaerobic series artificial wetland to deal with the sewage of Longkou NorthTown. The Project run continuously from April to December in2012. The mainresearch results summarized as follows:The entire processing of the pilot demonstration process includes four parts:Reservoirs, anaerobic baffled reactors, biological contact oxidation pond,aerobic/anaerobic series artificial wetland. We choose volcanic rocks as the filler ofartificial wetlands. We use aeration perforated pipe aeration. In order to reduce theprocess energy consumption, we research and development of intermittent windpower automatic aeration system to provide the aerationfor the whole system.Water quality monitoring results showed that the quality of effluent water was steady. The whole project has good removal efficiency on chemical oxygen demandand ammonia nitrogen. The chemical oxygen demand of effuent water varies from10.74mg L-1to20.7mg L-1, the ammonia nitrogen of effuent water varies from12.5mg L-1to18.8mg L-1. The removal efficiency of chemical oxygen demand andammonia nitrogen respectively were above95%and84.56%. The COD and NH₄⁺-Nof the effluent water can achieve a standard and two standard of <<Urban sewagetreatment plant pollutant discharge standard （GB18918-2002）>>. In the summer,NH₄⁺-N of the effluent water can achieve A B standard of <<Urban sewage treatmentplant pollutant discharge standard （GB18918-2002）>>.The intermittent wind power automatic aeration system can maintain aerobicenvironment of aerobic zone. The dissolved oxygen varies from2.3mg L-1to3.9mg L-1, it was the main process to remove ammonia nitrogen. Design of buried plasticfilm covering processing makes artificial wetlands anaerobic stage DO concentrationsvaried from0.3mg L-1to1.3mg L-1. Therefore, it improved the denitrificationfunction of artificial wetland.NH₄⁺-N removal efficiency was improved by the prolonged constructed wetlands（O:A:O=1:4:1）, the ammonia nitrogen of effuent water varies from12.5mg L-1to18.8mg L-1. Anaerobic part has great removal on NO3--N, the removal efficiency ofNO3--N was60.91%.The construction cost of the whole system was about95000yuan. Wind turbinecan satisfy the power consumption in the process of combination process operation,and in the second year running without input was basicaly realized. The project cantreat about3600tons domestic sewage every year. The project has goodenvironmental benefits, every year the project can reduce about1.6tons COD and0.33tons NH₄⁺-N. The project was easy to manage and it was an efficient sewagewater purification technology which was suitable for promotion typical of rural areasin northern China.