Optimization Of Centralized Treatment Technology For Village Domestic Sewage Based On Combined Weight GRA Method

In recent years,with the promotion of relevant national policies on the improvement of rural ecological environment,Hunan Province has increased the management of rural domestic sewage.However,due to the late start of the treatment of rural domestic sewage in Hunan Province,not only the lack of corresponding norms and technical guidance,but also the actual operational data for centralized treatment of village domestic sewage is very limited.Therefore,it is urgent to provide scientific and effective decision-making basis for the selection of centralized treatment technology for domestic sewage in villages in Hunan Province.Based on the current situation of centralized treatment of domestic sewage in villages in Hunan Province,an optimized evaluation system for combined weight GRA(Grey Relational Analysis)method was constructed to carry out eight alternative processes for centralized treatment of domestic sewage in Hunan Province.The preferred evaluation is based on the evaluation results,and the process of the alternative process that is more in line with the actual situation of Hunan Province.The main research results of the thesis are summarized as follows:(1)From the three aspects of economic benefit,technical performance and management operation,12 indicators were selected to construct a set of evaluation methods for centralized treatment of village domestic sewage in accordance with the actual situation of Hunan Province.With the three methods of analytic hierarchy process,entropy weight method and grey relational analysis method,a combined weight GRA method model was constructed to guide the evaluation of the centralized treatment technology of domestic sewage in villages in Hunan Prov ince.(2)Investigate the current situation of villages in Hunan Provin ce and the centralized treatment of domestic sewage,and conduct on-the-spot investigation and experiment on the existing domestic sewage treatment technology in Hunan Province,and at the same time combined the preferred techniques in other areas,the alternative technologies for centralized treatment of domestic sewage in accordance with the actual situation of Hunan Province are recommended,namely:Multi-level A/O process,Improved A~2/O process,Unpowered anaerobic+Constructed wetland,Improved A/O process,Fixed bed biofilm method,Biofilter+Constructed wetland+Stabilization pond,Anaerobic+SBR(Sequencing Batch Reactor activated sludge process)+Chemical phosphorus removal,Pretreatment+Artificial rapid osmosis.(3)According to the scale of sewage treatment,eight alternative processes are classified and evaluated by using the combined weight GRA method:The priority ordering of small centralizedprocesses(processing scale is 5~100 m~3/d)is:Improved A~2/O process,Biofilter+Constructed wetland+Stabilization pond,Unpowered anaerobic+Constructed wetland,Pretreatment+Artificial rapid osmosis,Improved A/O process,Multi-level A/O process,Fixed bed biofilm method,Anaerobic+SBR+Chemical phosphorus removal;The priority ordering of large centralized processes(processing scale is 100~500 m~3/d)is:Improved A~2/O process,Improved A/O process,Fixed bed biofilm method.