| Along with the rural regional economic development, the area-source pollution gradually becomes prominent. It caused graveness pollution of the lake body, it has become a threat to the national water environment security, and doing harm to the sustainable development of our society and economy. Rural area-source pollution has wide influence scope, large influence area, and randomness and concealment. The general mechanical and automatic wastewater treatment facilities and engineering could not be popularized and applied for it. Constructed wetland, being an ecological wastewater treatment technique, has advantages as follows - Low carbon, economic, beautiful and easy to operate, making it very suitable to be applied in treating rural area-source pollutions. This thesis relies on the subject'Poyang Lake Ecological Protection and Resource Use—Research and Demonstration of Water Pollution Control and Water Quality Protection Technologies', which belongs to the '11th-5' National Science and Technology Support Program. By combining the subject with the reality of rural area-source pollution in Poyang Lake district, we carried out the research on the wetland advanced treatment for rural area-source pollutions.As was showed in the PRA research in the lake area, the pollution source is becoming high load, especially a large number use of fertilizer and the random emission without effective treatment of livestock wastewater. Referring to the practical application of constructed wetland in the demonstration project of the subject, we have developed a series multi-stage vertical flow wetland which was aimed at treating high pollutant load rural area-source pollution wastewater, and conducted our research from the actual treatment effect, pollutant load and the way to enhance the treatment effect etc. Main conclusions are as follows:(1) By comparing the two demonstration constructed wetlands'pollutant removal effect, we found surface-flow constructed wetland has a low shock resistance capacity for the pollutants, namely that the water purification effect gets lower as the pollutant loads increase. When running under high pollutant loads, nitrogen and phosphorus removal is limited. (2) Aiming at the shortcomings of SFW which are poor shock resistance of the pollutant loads, this study proposes the self-designed series multi-stage vertical flow wetland to treat the rural non-point pollution source. The result shows that this equipment stability in operation with good quality effluent water, good at shock resistance of the pollutant loads and can meet the need of the rural non-point pollution wastewater treatment.(3) In the load bearing test for the wetland, we combining the demonstration constructed wetlands' influent concentration and the range of concentrations in survey results of PRA. we set differently graded pollutant load and hydraulic load and conducted analysis on the loads' influence on the purification effect and found that except for NH4+-N, the purification effect gets higher as the pollutant loads incease. We've established that in the ranging scope of the test, the best pollutant loads would be as follows:COD 100g/m2, NH4+-N 10g/m2, NO3--N 10g/m2, TP 5g/m2. For NH4+-N, the removal rate for is moderately higher under 5g/m2. Meanwhile, there's still room for improvement. We've also found that the fluctuations of hydraulic load could greatly influence the treatment effect, and finally established that the best hydraulic load should be between 0.3 and 0.4 m3/m2·d under the pollutant loads above.This also can indirectly educe that optimizing the load regulation can improve the water purification effect of the wetland system.(4) In the carbon source regulation test, we injected additional carbon source into the bottom of the constructed wetland through some special pipes to provide electron donors for the de-nitrification reactions. Meanwhile, we reduced the treatment load of the system, and saved the cost of carbon source addition. When the mass ration of COD and NO3-N was 5, the de-nitrification of the system boomed. It was concluded in the end that carbon source regulation on the system could enhance the de-nitrification effect.(5) In the Plant Growth's Influence on the System test, we found that compensational growth would be raised after the plants were reaped and a general increase in pollutants removal rate could be observed especially between the 18th and 26th days after the reaping - namely that the removal rate was the highest around the 3rd week. We've also found that the removal of different pollutants varies in the plants'growing period, and have preliminarily figured out the plant growth's contribution rate on different pollutants as follows:COD 17.9%, NH4+-N 11.2%, NO3--N 12.3%, TP 6.4%. It was concluded in the end that the purification rate of the constructed wetland is closely related to the plant growth in the system, and that we could enhance the wastewater treatment effect by controlling the plant growth in the system. |
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