Treatment Statu And Nitrogen And Phosphorus Control Technology Of Rural Domestic Sewege

Rural domestic sewage treatment has become an urgent need for comprehensive and harmonious development in today’s society.Through the study of the spatial and temporal distribution of the inlet and outlet of the rural domestic sewage treatment facilities in the demonstration area of Jiaxing City,the current status of rural domestic sewage pollution and treatment facilities is clarified.Based on this,further investigation of the response of lake-undulating water quality in the demonstration area to the effluent discharge of rural domestic sewage treatment facilities shows that the pollution of nitrogen and phosphorus in the lake water is closely related to the effluent nitrogen and phosphorus discharge of rural domestic sewage treatment facilities.The control of lake water pollution must start from the source,and it is imperative to improve the nitrogen and phosphorus removal performance of rural domestic sewage treatment facilities.Among them,constructed wetlands plays an important role in rural domestic sewage treatment.Based on the idea of combining rural domestic sewage treatment with the resource utilization of black and smelly sediments,the sediment was modified by means of HNO₃ oxidation and loaded with sodium ions,and the nitrogen and phosphorus adsorption properties of the modified sediment material and its application prospect as a constructed wetland filler in the treatment of rural domestic sewage were studied.The main conclusions are as follows:（1）The nitrogen and phosphorus of rural domestic sewage and the effluent from rural domestic sewage treatment facilities in the demonstration area of Jiaxing city are severely polluted.The annual mean concentrations of the characteristic pollutants COD,NH₃-N,TN,TP are 142.23 mg/L and 74.42 mg/L,27.74 mg/L and 14.29 mg/L,44.19 mg/L and 29.03 mg/L,4.02 mg/L and 2.89 mg/L,respectively.In addition,the spatial and temporal distribution of characteristic pollutants of rural domestic sewage and effluent from rural domestic sewage treatment facilities in the demonstration area both show significant differences.Among them,Haining City and Xiuzhou district show the distribution characteristics of gradually decreasing from west to east and from north to south,respectively.Seasonal distribution is reflected as:（1）Winter>（2）Spring>（3）Autumn>（4）Summer.Defining the temporal and spatial distribution rules of characteristic pollutants can realize the priority management and control of severely polluted time seasons and spatial areas,and achieve the effect of pollution prevention and early warning.In addition,the overall removal effect of the characteristic pollutants from the rural domestic sewage treatment facilities in the demonstration area of Jiaxing City failed to meet expectations.The average annual removal rates of COD,NH₃-N,TN,TP were 50.5%,51.7%,36.8%and 29.7%,respectively.And the removal effect of rural domestic sewage treatment facilities on characteristic pollutants is significantly affected by seasonal changes.The seasonal distribution of pollutant removal rate is reflected as follows:（1）Summer>（2）Autumn>（3）Spring>（4）Winter.（2）The nitrogen and phosphorus in the lake water of the demonstration area in Jiaxing City is severely polluted,and most of them are inferior to categoryⅤwater.The overlying lake water and the sediment are seriously polluted with nitrogen and phosphorus,and the interstitial water in the lake has the basis for the release of the pollutants in the sediment to the overlying water.The correlation analysis results show that the nitrogen and phosphorus in the lake water and the removal rate of nitrogen and phosphorus in rural domestic sewage treatment facilities are significantly negatively correlated,and the correlation coefficient is in the range of-0.884?-0.918.Meanwhile,the nitrogen and phosphorus in the lake water and the effluent discharge of rural domestic sewage treatment facilities are significantly positive correlated,and the correlation coefficient is in the range of 0.822?0.980.The discharge of nitrogen and phosphorus from the effluent of rural domestic sewage treatment facilities in the demonstration area of Jiaxing City has a great impact on the nitrogen and phosphorus pollution of lake water.（3）The sediment was modified by means of HNO₃ oxidation and loaded with sodium ions,and the nitrogen and phosphorus adsorption properties of the sediment material have a greatly improvement.The adsorption performance is reflected as follows:OMS（oxidation-sodium-loaded combined modified sediment）>OS（oxidation modified sediment）>MS（sodium-loaded modified sediment）>S（original sediment）.Among them,the specific surface area and pore size of OMS have significantly increased,reaching 30.07 m²/g and 6.89×10^-2mg/kg,respectively.Moreover,the removal rate of NH₃-N and TP by OMS reaches more than 85%and 92%respectively.Study on nitrogen and phosphorus adsorption of sediment materials shows that the quasi-second-order kinetic adsorption model and the Langmuir adsorption isotherm model can better describe the adsorption kinetics and adsorption isotherms of nitrogen and phosphorus by sediment materials.The adsorption of nitrogen and phosphorus by sediment materials is affected by temperature.Within an appropriate range,a higher temperature is beneficial to the adsorption of nitrogen and phosphorus by sediment materials.At 35°C,the maximum adsorption capacity of OMS for NH3-N and TP reached 0.90 mg/g and 0.49 mg/g,respectively.Compared with the common nitrogen and phosphorus adsorbents on the market,OMS has certain competitiveness.Therefore,with OMS as the breakthrough point,OMS and the original constructed wetland filler were mixed in a 1:10 ratio to optimize the rural constructed wetland filler.It was found that the nitrogen and phosphorus removal performance of the rural domestic sewage treatment facilities has improved significantly.The removal rate of the nitrogen and phosphorus reached 72.1%and 64.5%,respectively,and the nitrogen and phosphorus in the effluent of the rural domestic sewage treatment facilities all met the level one B discharge standard of"Discharge standard of Pollutants for Municipal Wastewater Treatment Plant"（GB18918-2002）.In addition,the cost of OMS preparation reagents is 40.23 RMB/kg,which has certain competitiveness compared with the natural adsorption materials and some modified materials commonly available on the market.It shows that OMS has an great application prospect in optimizing rural constructed wetland fillers to reduce nitrogen and phosphorus in rural domestic sewage.In addition,the cost of OMS preparation reagent is 40.23 yuan/kg,which has certain competitiveness compared with the common natural adsorption materials and some modified materials in the market.It shows that OMS optimization of rural constructed wetland filler to reduce nitrogen and phosphorus in rural domestic sewage has a certain application prospect.