Study On The Method Of Water Quality Comprehensive Evaluation And Water Environmental Capacity Calculation Of River In The Flood Season

Recently China is in a period of rapid urbanization. With the rapid development of economy and urbanization, the problem of eutrophic river caused by non-point source pollution is increasingly critical. Total amount controlling pattern of pollutant has more advantages than consistency controlling pattern in solving non-point source pollution in water. This paper took the upstream of the Haihe River(from Sanchakou to the Haihe Bridge) in Tianjin as the research object. In view of the characteristics that the upstream of the Haihe River on the eutrophication problem and water pollution during flood period, the water quality was quantitative evaluated, the environmental capacity during flood season was calculated, the reduction amount of pollutants in the rainwater was determined, and made comparison of the engineering and technical means of pollution control, the scheme to control pollution and improve water environment quality was put forward. The main research content is as follow:(1)By analyzing and comparing the existing all kinds of water quality evaluation method, an artificial fish-swarm neural network water quality evaluation model was proposed based on the artificial fish swarm algorithm method and BP(Back Propagation) neural network method according to the characteristics of the study area. The model was applied to the water quality assessment in mainstream of the Haihe River. The qualitative and quantitative analysis was carried out to the pollution status of each section in the upstream of the Haihe River.(2)In order to study the attenuation of water quality, a one-dimensional steady-state attenuation of water quality model was chosen to simulate the dilution, diffusion, migration and degradation rules of water body according to the characteristics of the research object. The water environment capacity and reduction quantity by the indexes of COD(Chemical Oxygen Demand), TN(Total Nitrogen), NH3-N(Ammonia Nitrogen), TP(Total Phosphorus) were calculated based on the material balance calculation model.(3)Analyzed the technical, social, economic and other aspects of the Haihe River upstream factor. Engineering technology method of water environmental capacity enhancement and water quality improvement at home and abroad was screened, then put forward the water environment quality improve scheme.