Pilot Study On Agricultural Non-point Source Pollution Control Project In Hunan Province

Agricultural non-point source pollution in Hunan Province has gradually become one of the causes of river basin water pollution.At present,there are no mature technical regulations for the treatment of agricultural non-point source pollution.It is necessary to develop a comprehensive control technology system for agricultural non-point source pollution in Hunan Province based on the study of rural non-point source pollution.For this reason,this paper read a lot of relevant literature,extracting the theoretical basis of agricultural non-point source pollution generation and prevention in Hunan Province.On this basis,the present situation of agricultural non-point source pollution in Hunan Province and its engineering treatment technology are analyzed.Taking the control of agricultural non-point source pollution in Caoping Town of Dingcheng District of Changde City as the research object,the special main sources and pollutant emissions of agricultural non-point source pollution in Caoping Town of Dingcheng District of Changde City are analyzed.Based on the different characteristics of seven pilot basins,the application of ecological control and control are studied and designed.Engineering design scheme of agricultural non-point source pollution control combined with resource utilization.The results are as follows:1.The main environmental characteristics of the small watershed of Wuangshui River in Caoping Town,Dingcheng District,Changde City,Hunan Province,are the large proportion of farmland and the well-developed Pool Noun.There are seven tributaries of the Wuangshui River.The agricultural non-point source pollution characteristics of the pilot area covered by seven independent tributaries in the upper reaches of the small watershed of the Wuangshui River are low sewage treatment rate,serious direct drainage,high planting intensity of farmland and the input of chemical fertilizers and pesticides.Large amount of input and discharge,large but scattered total livestock and poultry farming,serious waste treatment and low utilization rate of resources,etc.The total COD emissions,ammonia nitrogen emissions,total nitrogen emissions and total phosphorus emissions in the pilot area are 750.6 tons/year,63.9 tons/year,125.4 tons/year and 18.4 tons/year respectively.The main non-point source pollution in this basin is livestock and poultry manure discharge.Among them,COD,ammonia nitrogen,TN and TP pollution loads are the highest,which are 452.4,44.9,98.1 and 19.0 tons/year respectively,accounting for 57.7%,69.0%,76.5%and 86.5%of the total pollution discharge,respectively.Through the construction of the agricultural non-point source scheme designed in this paper,the environmental impact of agricultural production on the pilot area can be reduced from the source,so that the use of fertilizers and pesticides in the pilot area can be reduced by more than 20%,the utilization rate of livestock and poultry manure can reach more than 90%,and the emission of chemical oxygen demand,total nitrogen and total phosphorus can be reduced by more than 40%,30%and 30%respectively.2.According to the distribution characteristics of farmland and runoff system in seven tributaries of the Huangshui River,different pollution control engineering technologies are designed and mixed.Mainly including village surface runoff sewage purification and utilization project,farmland non-point source pollution prevention and control project,livestock and poultry breeding pollution control project,including village surface runoff sewage purification and utilization project includes four purification pond technology,surface flow constructed wetland technology,farmland non-point source pollution prevention and control project includes ecological ditch interception engineering technology,surface flow wetland engineering technology,livestock and poultry breeding pollution control project.The project includes dry and clean dung technology,green foxtail algae wetland engineering technology and so on.Combined with the treatment and resource utilization of solid and liquid discharges from aquaculture farms,the treatment of polluted runoff system around aquaculture farms,and the utilization of wetland plants,etc.3.The specific scale of various engineering projects in this project design is as follows:(1)Surface runoff sewage purification and utilization project:new ecological ditch 0.136 km5 surface flow ecological wetland 4,new water retaining sill 4,wetland ecological slope 881 m2.There are 300 sets of four-tank purification system for rural domestic sewage treatment.(2)Prevention and control of non-point source pollution in farmland:2.821 km of new ecological ditches,20 surface-flow ecological wetlands,3192 m2 of wetland ecological slope protection,20 new water retaining sills and 16 ecological floating beds.There are 100 new farmland waste collection pools.(3)Livestock and poultry breeding pollution control projects:1 wastewater treatment project around 5000 farms,1 wastewater treatment project for 2000 farms,1 wastewater treatment project for 1000 farms and 2 wastewater treatment project for 400 farms.