Benefits From Comprehensive Treatment Project Of Lakes In Southwest China

Since the "eleventh five year plan" in China, "green water action" is carried out vigorously in Chongqing now. On June 7, 2013, the municipal government issued?the environmental protection " five actions " plan in chongqing(2013-2017) ?. The built up area lake reservoir water environment comprehensive improvement is the main points of "green water action", which is one of environmental protection "five actions" in Chongqing. Caiyun Lake Reservoir is one of the first lake reservoirs in Chongqing comprehensive improvement of water environment, whose major source of pollutants are nonpoint source pollution in urban runoff?sediment pollution? sewage pollution brings by inadequate pipe network and water pollution in the water facilities. According to these sources of pollutants,we take some measures to governance the lake, like improving the pipeline network system, hydrating engineering restore and strengthen, urban runoff pollution reduction engineering, ecological dredging sediment engineering, ecological engineering bay, reoxygenation living water engineering,blooms emergency disposal engineering.This topic selected five representative sample points in Caiyun Lake to monitor its CODcr, TN, TP and NH3-N, chlorophyll a, transparency(SD), DO for a period of eight months, which is before and after the Caiyun Lake environmental comprehensive. In the monitoring phase, in addition to the ecological engineering bay is not implemented and still in the experimental state, other engineering measures are completed.Before the environment comprehensive management in Caiyun Lake, CODcr?NH3-N?transparency(SD)?DO were 38.8 mg / L? 1.35 mg / L? 0.71m?5.18 mg / L, had met the surface water environment five-water standards(CODcr?40 mg / L, NH3-N?2 mg / L, SD?0.5 mg / L, DO?2 mg / L), and TN?TP? chlorophyll a were 10.91 mg / L? 1.21 mg / L? 0.082 mg / L,they did not meet the surface water environment fivewater standards(TN?2 mg / L, TP?0.2 mg / L, chlorophyll a?0.06 mg / L). After the environment comprehensive management in Caiyun Lake, each pollutant index have been certain cuts,the mean of chlorophyll and TP are 0.050 mg / L and 0.18 mg / L,which meet the surface water environment five-water standards; the mean of TN is 5.11 mg / L,which although do not reach the surface water environment five-water standards,but but relative to management before 10.91 mg/L, has been greatly reduced.After the environment comprehensive management in Caiyun Lake, CODcr,?NH3-N? TN and TP pollution reductions were 1117.68 t/a? 63.26 t/a? 306.38 t/a? 54.41 t/a.In each engineering measures, CODcr?TN?TP removal rate of the ecological dredging sediment engineering were highest of 34.92%?59.24%?77.93%, so it make the greatest contribution of CODcr, TN, TP pollutants reduction in all measures; NH3-N removal rate of urban runoff pollution reduction was 42.29%,because NH3-N concentration in urban runoff is measured high and has a great influence on the concentration of NH3-N in the lake,so urban runoff pollutants reduction project can reduce this part of NH3-N pollution greatly. From all the pollutants removal ratio, ecological dredging sediment engineering and urban runoff pollution reduction across the Caiyun Lake water environment comprehensive treatment occupy the important position.From the point of the whole Caiyun Lake water environment comprehensive treatment engineering, CODcr?NH3-N?TN?TP engineering direct investment benefit of pollutant to cut costs, is respectively 0.0952 t/a/ten thousand yuan, 0.0054 t/a/ten thousand yuan, 0.0261 t/a/ten thousand yuan, 0.0046t/a/ten thousand yuan. From a single control engineering measures,improving the pipeline network system in CODcr and NH3-N investment cost cuts in benefits is highest,which is respectively 0.1790 t/a/ten thousand and 0.0128 t/a/ten thousand yuan, ecological dredging sediment engineering in TN and TP investment cost cuts in benefits is highest,which is respectively 0.0369 t/a/ten thousand and 0.0086 t/a/ten thousand yuan. From the point of project investment cost reduction benefits pollutants, improving the pipeline network system and ecological dredging sediment engineering throughout the Caiyun Lake water environment comprehensive treatment occupy the important position.In the process of Caiyun Lake water environment comprehensive treatment, the various engineering measures played an important role in pollutant reduction, each pollutant concentrations in Caiyun Lake are reduced to a certain extent, water clarity and dissolved oxygen also increased, the water environment of Caiyun Lake has been greatly improved. From the point of economic, each measure is in line with the economic viability of the project. So the comprehensive environmental management in Caiyun Lake can be used as a template in southwestern region of lake reservoirs treatment, drawing on its engineering control measures according to their own conditions, and can be adjusted as appropriate.