| Due to the effects of poultry raising, agricultural activities, industrial pollution, urban waste, the water quality of Liangtan river is worse than Grade V, seriously affecting the water safety of drinking and irrigation in the coastal regions. Moreover, Liangtan river is an important first class tributary of the Jialing river in Chongqing, which is the main source of drinking water of Chongqing city. And the deterioration of water quality in Liangtan river is bound to have a great impact on water quality of the Jialing River, and then threaten the safety of drinking water in Chongqing City. Jialing River is also the second largest tributary of the Yangtze River and located in the heart of the Three Gorges reservoir area. So water quality of Liangtan river also has certain influence on that of the Three Gorges Reservoir. Given the importance of this river, the remediation of Liangtan River has attracted great attention from the Chongqing Municipal Government.Situ remediation technology is an emerging technology that is widely used in lakes, reservoirs and other stationary water bodies, while using it for river restoration is still a challenge. The achievements of pilot study would open new roads for river remediation in Chongqing.This pilot study used artificial riverbank protection technology, general floating island, aquatic complex ecological floating island and stocking techniques.Cannas were used as riverbank protection plant in riverbank protection technology and their leaves covered more than 75% of the riverbank protection areas. Compared with the control section, canna had a good interception ability for pollutants. In the early stage of the formation of rainfall runoff, the removal rate of SS, TN, TP and COD were 40.48%,12.24%,1047% and 11.05% in the canna-planted area. However, the effects of interception decreased when soil is saturated by water. Ordinary floating island used foam as a carrier to plant cannas. This material is anti-aging but has bad impact resistance. Floating island could purify river to a certain degree, and the removal rates of COD, NH3-N, TP and Chl-a were 14.95%,9.77%,8.86% and 12.96%, respectively. The removal effects of floating islands had much to do with the weather, in the same temperature conditions:weather and flow rate determined the removal effect of pollutants when the temperature in the same range;in the same weather conditions, temperature and flow rate determined the results; with the same flow rate, temperature and weather conditions played the main roles.The technology of Complex ecological floating island used high light foam board as the carrier and planted windmill grass in gravels, and then connected with the biofilm for indigenous microbe. This technology was anti-aging and had good impact resistance, and increased microbe greatly in the floating.So a good purifying effect could achieved,and the removal rates of COD, NH3-N, TP and Chl-a were 22.06%,15.68%,16.81% and 14.77%,respectively.According to actual situation of the water, aquatic animal stocking technology used scavenger food chain animals-catfish as stocking object. Although the purification was not obvious, catfish could prevent deterioration of the water to some degrees. So catfish could be used as pioneer animal in the remediation of seriously polluted river.When all technologies were used jointly, the lowest removal efficiency of COD was 17.73%, and the highest was 36.06%, with an average of 28.02%; the lowest removal efficiency of NH3-N was 5.63%, and the highest was 24.30%, with an average of 15.29%; the lowest removal efficiency of TP was 9.84%, and the highest was 24.18%, with an average of 16.71%; Chl-a removal rate was up to 23.84%. In addition, algae could be removed stably, and the maximum response rate of DO was 6.98%. And these technologies had no influence on the pH of water. The results showed that this project could purify the water from worse than Grade V to V, indicating that it is feasible in situ remediation for river.
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