| Rural domestic sewage has become the main pollution sources of water in our country. The key to the study in water pollution control engineering is the treatment of rural domestic sewage, because of its large difficulty of pollution sources controling and collecting. Research shows that, the anaerobic treatment be widely used in rural domestic sewage treatment in China and abroad. The anaerobic treatment technology could adapt high concentration of organic wastewater treatment, but the treatment efficiency is poorer, and the water quality index cannot reach the require of reuse water. The traditional artificial wetland is another treatment technology used to deal with the rural domestic sewage because of its low cost and easy managemen. Yet artificial wetland has lots of problems, such as covering larger area, tolerance of low pollutant concentration, easy to appear blocking and mosquito stench phenomenon, and so on. Analyzed the advantages of these two processes, the improved and simplified A2/O-artificially subsurface flow wetland combination treatment system has been proposed to deal with rural domestic sewage. And the treatment efficiency and technological parameters of the combined process is the main research content.This experiment project is located at a rural areas in Yunnan province.The experiment period continued from May 2009 to January 2011.The operational effect of combined system with improved A2/O reactor and Artificial Subsurface Flow Wetland (A2/O-SSFW) including the removal effects of CODCr, BOD5, SS, nitrogen and phosphorus were analysed in this research. And the role of the plants and stroma type were also investigated. All analysis showed that the best rate of sludge return was 150%, the best sludge retention time was 12d in oxic zone, and the proportion between anoxic zone and oxic zone was 2:4. The optimal proportioning of wetland stroma between cinder and gravel was 3:7. Through plant selection, canna was choosed to be the best species. the best hydraulic resident time(HRT) was 30h. The experimental results revealed the average removal rate of CODCr, BOD5, TN, NH3-N and SS of A2/O-SSFW were 80.5%,84.3%,91.8%,93.2% and 86.4% respectively. Because of the stroma wihich can adsorb phosphorus efficiently was mixed in the wetland, the removal rate of TP retained above 75.7% throughout. As a result of the plant biomass was great in summer and autumn, the removal rate of TP achieved 80.1%.The climate is mild in the project location. The temperature, averagely about 15℃, is higher in winter. The removal rate of COCr was slightly reduced to about 72.5% when temperature dropped dramatically in winter, which was lower than in summer and autumn. Sometime, the consistence of CODCr in outflow would be a little higher than Level-1-B standard. The quantity of sewage will reduce because it is arid in winter in Yunnan province and the water amount of usage is very small. The HRT can be suitably prolonged to guarantee the CODCr consistence in outflow lower the standard.The experiment result shows that the improved A2/O- artificial subsurface flow wetland has advantages as follow. (1) It can save energy and cut the maintenance costs because the require of water quality was lower in improved A2/O at the front side and the process can be greatly simplified. At the same time, it can help reduce the treatment load of artificial subsurface flow wetland and it also can reduce the area of wetlands. (2) After treating by the improved A2/O, it can reduce the suspended solids in sewage significantly, which can reduce the possibility that clogging of the artificial wetlands. (3) The treatment performance of wetland has been improved by the screening of stroma and plants in artificial wetland. So the internal biomass also increased significantly and the treatment efficiency of the wetland has been improved. (4)The combined process, having landscape features, could beautify the environment which meeting the needs of new rural development. |
PDF Full Text Request