Study On Pattern Of Decentralizing Point Source Wastewater Treatment Plants Along Yuxiu River

With the development of economy and urbanization, point and no-point source polluted water discharged to urban stream degrade its ecosystem so that it is incompatible with its surrounding. Restoring the degraded aquatic ecosystem is very necessary to every city. This paper focuses on Yuxiu River (Jinan, China) restoration project and provides an available pattern to improve its aquatic ecosystem. The effluent from point source wastewater advanced treatment station online is supplied to meet stream ecological requirement for water and restrain algae to avoid eutrophication.Based on analyzing and comparing the restoration patterns and technological methods of rivers/streams in China and other countries, this paper demonstrates the new pattern that not only eliminates point resource water pollution, supply enough water resources with better quality but also be suitable for the city with limited space. After studying on pattern of decentralizing point source wastewater treatment plants along Yuxiu River, we drew six conclusions as followed. 1)Three stages about drainage system are summarized which is drainage in disorder early, centralized wastewater treatment and discharge, and wastewater treatment and discharge or reuse online at last. It is shortening water resource that drives the drainage system forward from centralization to decentralization and reclaimation online. Centralizing urban sewage treatment and its corresponding drainage system is analyzed. Aiming at its flaw, a new idea has been put forward which is decentralizing point source wastewater treatment along urban stream to restore the polluted aquatic environment and relieve water absence. 2) Based on the theory of decentralizing wastewater treatment, study on index to restore the urban stream ecosystem and the environment water requirement has been done. Water quality to be leaded depends on the function of receiving water body such as the effluent that is going to be leaded into urban stream to improve its aquatic environment from wastewater treatment plant. Chlorophyll-a is selected as the index to show the ecology status of Yuxiu River in this paper. The measurement of decreasing the concentration of nutrient limiting factor is taken to restrain the growth of phytoplankton in the receiving water body according to the principle that organism growth depends on the most lacking nutrient factor. That nutrient limiting factor just is the effluent parameter to be controlled emphatically. The parameter will be also used to calculate and get flow requirement.3) Typical data of 10 indexes for Yuxiu River from May to November are collected such as chlorophyll-a, COD, TN, NH4+-N, NO3--N, NO2--N, TP, PO4-, DO and Temperature under the dynamic condition. The relationships between Chlorophyll a and other 9 chemical and physical water quality parameters in Yuxiu River are studied by gray relation analysis. Furthermore, the relationships are also observed under the static condition in laboratory. These results indicate that ammonia is a more important nutrient limiting factor than others for the growth of phytoplankton.4) The model for computing flow of wastewater treatment units is built according to one dimension model for pollutant transference and transformation. The simulation results show that the maximum effluent ammonia concentration is 2.8 mg/L if wastewater treatment plants are built as followed: 12 000m~3/d, in Baliwa Road sector, 2 000m~3/d, in Shunyu Road sector and 3 000m~3/d, in planting garden. The ammonia concentration of receiving water body will be under 2.0 mg/L, which get toâ…¤of surface water quality criterion.5) Critical distance is used to compare the scale benefit from centralization form and reuse water pipage from decentralization form on Yuxiu River, and result show that the pattern of decentralizing point source wastewater treatment along urban stream is prior to centralization.6) Based on reviewing the development of wastewater treatment process and analyzing different characteristic of enery process, four types of processes are summarized, which is suitable to be applied to the Yuxiu River. They are BAF, SBR, MBR and A/A/O. At the same time, rules of these processes to be applied are concluded.The influent and effluent water qualities are analyzed for three-wastewater reclamation station from May to November in 2006. The results show the effluent ammonia concentration provided by the ETS and BAF process is below 2.8 mg/L, which will facilitate restraining the growth of phytoplankton in the Yuxiu River.The pattern of decentralizing point source wastewater treatment plants along urban stream is more consummated through this research. The research route and result may be quoted to restore other urban streams and be in favor of facilitating the development of restoration idea and technology.