| BaiYiAn Stream, located at the Northeast part of BaiYi town, is one of the eight Permanent streams within XiMaoLi Lake basins. In BaYi town, boasting convenient transportation, there is a county-level main road going through north and south, with a provincial roadway to its east. Developed industry and agriculture along with a lack of environment protection has resulted in the environment degradation and heavy pollution of BaiYiAn stream. Based on this situation, this paper will do the analysis and design towards the process control area and the lake entrance of BaiYiAn stream and XiMaoLi Lake in Changde, Hunan province.According to the features and general requirements of the Technical guide for the lake ecological environmental protection, lake ecological restoration and the building of constructed wetland, the author has done survey of the process control area and the lake entrance, which shows:BaiYi county covers a land of 85 square kilometers with a population of 24.2 thousand people, which is predicted to reach 25.2 thousand in the year 2020; and the agriculture is mainly of rice, rokkyo fruit and citrus. According to the survey, the COD (Chemical Oxygen Demand) loss amount of BaiYiAn stream is about 406.21t; the NH3-N loss is 81.24 t; TP loss 10.15t and TN loss 121.86t; and the domestic sewage discharge of urban residents is about 151767 t per year. Based on the knowledge of Landscape Ecology, landscape planning theory, the idea of how to build constructed wetland, along with the case analysis of both at home and abroad, this paper has oriented the overall goal of the BaiYiAn stream design and got the conclusions that:there should build a demonstration park setting the'resource utilization of wetland sewage' and'ecological landscape construction'in one, covering a land of 200,000 square kilometers; the core characteristic should be the "Red maple plant sight", along with the topics of wetland protection & recovery and Popular Science Education, which will not only meet the demand of supporting construction around the wetland, but also the residents' leisure and entertainment needs.Through summarizing and analysis, while based on the current situation, the BaiYiAn stream is divided into several areas as River Ecological Restoration Area, River Beach Restoration Area, Wetland Experience Area, Water Treatment Demonstration Area, Constructed Wetland Area and Aquatic Vegetable Growing Area. Meanwhile, this paper will do the respective design in terms of river ecological restoration, constructed wetland, plant ecological restoration, Aquatic vegetable cultivation, road engineering, river dredging, hydraulic structures and embankment protection. Following the original river shape, we have finished proper river restoration, districted the river plane according to the real situation, and added natural ecological beach, river course, eco island and constructed wetland, based on which, we do the design of both cross and vertical sections of the river channel; meanwhile, taking the sewage treatment capacity of the original channel into consideration, we have designed the constructed wetland. We manage the secondary effluent through method of 'Surface and Undercurrent constructed wetland'; and deal with the BaiYiAn stream with method 'Surface current constructed wetland'. In addition, the eco pond, being used to remove the Nitrogen and Phosphorus in the water, will become a landscape and water type ecological barrier for BaiYiAn stream. Through the method 'Surface and Undercurrent constructed wetland', we have calculated that the active area of surface and undercurrent constructed wetland is about 1,400 square meters; the design flow is 800 m3/d; the hydraulic retention time is about two days. Meanwhile, when managing the stream through the method 'Surface current constructed wetland', we have concluded that the active area of the stream is about 11,400 square meters; the design flow is 1800 m3/d; the hydraulic retention time is about three days. So, the total area is 12.800 square meters, and the monthly TN, TP absorption is 960 kg, and the annual is 11,500kg.Besides that, combining the river ecological restoration and wetland building, this paper has successfully managed the water quality of the process control area of the lake's upper reaches and reduced the silt deposit; and then, after constructed wetland management, this water can be used as landscape water for MaoLi lake, with the water quality of lake-entrance reaching the level of 3-grade surface water. In addition, bounded with features of eco-system and characteristics of historical and cultural resources, this paper is making great efforts to put up with the both municipal and provincial famous river ecological restoration design. |
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