The Recent Status Of The Urban Wastewater Treatment In China And The Paths Of Upgrading And Reconstruction For The Urban Sewage Treatment Plants Example Of Liaoyang Sewage Treatment Plant

In recent years, with the improvement of our country urbanization level, discharge of urban sewage increasing, urban water pollution problem increasingly serious, the current situation of our country’s urban sewage treatment is not optimistic. Urban sewage treatment plants as urban sewage treatment infrastructure, faces enormous pressure and challenges. In order to reduce the pollution of water environment, "the urban sewage treatment plant pollutant discharge standard"(GB18918-2002) was implemented, which published by Ministry of Environmental Protection. Before the implementation of the new standard, most of urban sewage treatment plants in our country were designed according to the level 1 B emission standard, and they can hardly up to level of A standard. So the urban sewage treatment plants are facing the problem of upgrading and reconstruction.The mainly content of this thesis is divided into three aspects, respectively are the comprehensive summary to the analysis of current urban sewage treatment in our country and summarized the paths to upgrading and reconstruction of urban sewage treatment plant and then making case analysis with the examples of Liaoyang sewage treatment plant. Activated sludge process was adopted by most of the early construction of sewage treatment plants in China, but its removal rate for nitrogen and phosphorus is too low to meet the level of A standard. The paths of upgrading and reconstruction for the urban sewage treatment plants in our country to improve this situation are mainly four aspects that are to adjust the original activated sludge process, increase the membrane treatment process, increase the chemical phosphorus removal process and increase the depth treatment technology. First phase project of Liaoyang sewage treatment plant adopted AO process and Its effluent standards is the criterion for level 1 B. Compared to first phase project, the main change of the second phase project is adjust AO process as the AAO process at the same time increased the membrane treatment technology. After the upgrading and reconstruction for Liaoyang urban sewage treatment plants, the processing out of the water can steadily reached to the level A emissions standards.