The Design Of The OLD Canal Composite Undercurrents Wetland For Advanced Municipal Sewage Treatment

The South-to-North Water Transfer Project is a key program to solve the scarcityof water resources in north China. The water quality will play a vital role in watersecurity of the South-to-North Water Transfer Project. Nansi Lake is the importantpassageway of the South-to-North Water Transfer Project (east route) of ShandongSection. After years of efforts, the water quality of Nansihu Lake was continuallyimproving. Although monitoring results for2010show that about70%of Nansi Lakearea reached Grade ⅣtoⅤ, it still have greater disparity with the requirements standard(Grade III). As an appropriate ecological treatment to treat polluted water, constructedwetlands are generally used for treating domestic and some industrial waste water.Wetland water purification project can effectively degrade water contaminants, reducethe lake eutrophication, improve water quality, increase the environmental capacity ofrivers and recover the natural ecology of river. For the old canal water quality has animportant impact on the water quality of Nansihu Lake, constructed wetlandsconstruction of the old canal water purification project, which can help to improve thewater quality of Nansihu Lake, and to ensure the long term stability of water quality ofthe South-to-North Water Transfer.In this study, based on the investigation and analysis of area economy, naturalstatus and water pollution status of the old canal constructed wetland project, thepreliminary design of the old canal complex subsurface flow constructed wetland waterpurification engineering was accomplish. This program initially selected the position of theconstructed wetland project. The old canal water purification constructed wetlandproject covering an area of148.2ha, treatment capacity is55,000m3every day, and14,744,000m3each year. The principles of this design are technical stability,economically feasible and easy to use and manage. Based on these principles, thetechnical proposal of the old canal wetland water purification process engineering programis composite subsruface flow constructed wetland, surface flow constructed wetland,combined stabilization pond technology.When the old canal wetland water purificationproject completed, there will be in total of about603.2tons CODcr,120.6tons BOD5,281.5tons TN and6.0tons TP reduced each year. When old canal wetland waterpurification project is completed and stable operation, there will be receipts of3.88million yuan generated by the plant and0.9million yuan generated by fish each year. After the implementation of the project, water quality of old canal will be significantlyimproved, and water quality of South-to-North Water Transfer Project (east route) willbe effectively improved.