Study On Nonpoint Source Pollution Of The Middle Area Of The Haihe River

The development of the middle area of Haihe has influenced the development of Tianjin and is playing an increasingly important role.In recent years,with the effective control of point source pollution,nonpoint source pollution has become an important cause of river pollution in the middle area of Haihe.Base on the research of nonpoint sources at home and abroad and the background of middle area of Haihe,this paper aims at the research of nonpoint source pollution control.This study adopted suitable measure to estimate the COD,TN and TP pollution load,and selected the nonpoint source pollution control measures for the middle area of Haihe.Further,based on the water environment capacity,the paper proposed reasonable pollution reduction and optimization scheme.This study not only fills the blank of nonpoint source pollution in middle area of Haihe but also has great contributions to improving the water environment quality and regional development.In this paper,the method of pollution discharge coefficient was used to estimate the nonpoint sources pollutions of agriculture runoff,urban runoff,aquaculture and rural life.The results show that rural life pollution and urban runoff pollution are the main sources of pollution and COD pollution in the middle area of Haihe,respectively.Xianshuigu Town is the main contribution area.At the same time,the pollution load is concentrated in June,July,August and September.And most areas are in a relatively low pollution state,only a few areas in a high pollution state.And the high pollution areas are mainly distributed along rivers.Based on comprehensive coefficient method,the technology of constructed wetland,rainwater garden,complex filling sequencing batch biofilm and plant-microbe complex for treating field drainage are selected for treating rural life,urban runoff,aquaculture and agriculture runoff pollution.The Haihe River is reduced to a one-dimensional water quality model in the paper,and the water environmental capacity and emission reductions are calculated for each sub-region.Shuanggang Town has the largest water environmental capacity and Xinli Street has the largest pressure to reduce emissions.Taken the water environmental capacity of each subregion as the constraint and the COD reduction cost as the objective function,the optimization models on pollutant emission reduction and cost optimization of the middle area of Haihe were established.The results showed that it can be reduced by 4073.48 t COD and the total cost of 25.7513 million yuan per year.Further,the reduction areas mainly concentrated in villages,industrial and commercial areas along river.