Construction And Empirical Study Of Performance Evaluation System Of Urban Non-point Source Pollution Control Engineering

Lakeshore zone is a transitional zone between the aquatic ecosystem of lakes and rivers and the terrestrial ecosystem.It can intercept,settle and purify pollutants.Therefore,how to improve the ability of lakefront to remove pollutants has become the current research focus.In this paper,the enhanced water purification efficiency of lakeside zone in Baiyangdian area is taken as the research object.In terms of water purification efficiency,the water purification efficiency was compared and studied under the conditions of different pollution loads,hydraulic retention time and temperature by setting biochar content,dry reed stem content and plant configuration in three experimental groups.Since the growth and activity of aquatic plants will also be affected under different conditions,the plant height and enzyme activity will be determined to further characterize the effects on plants.The mechanism of water purification was analyzed from two aspects:net nitrogen transformation and microbial community change.The results showed that the addition of I%dry reed stem and 3%biochar in the matrix could withstand the removal of total nitrogen and total phosphorus under high pollution load,with total nitrogen concentration of 10.0-12.0 mg/L and total phosphorus concentration of 0.2-0.3 mg/L under high pollution load.And be able to tolerate 1-3? low temperature under the condition of total nitrogen and total phosphorus removal,total nitrogen concentration of 5.5 mg/L,the water total phosphorus concentration in the water is 0.13 mg/L.The hydraulic retention time has a great influence on total nitrogen and total phosphorus.When the hydraulic retention time is 24 hours,the removal effect of total nitrogen and total phosphorus is the best.The influent concentration of total nitrogen is 2.7 mg/L,the effluent is 0.4 mg/L,the influent concentration of total phosphorus is 0.20-0.25 mg/L,and the effluent concentration is 0.03 mg/L.For plant configuration,the effluent of cultivated plants in the substrate is obviously lower than that of uncultivated plants,but the planted plant species has little influence on the water purification effect.In terms of purification mechanism,the addition of dry reed straw and biochar can increase the nitrification rate of bacteria and the number of functional bacteria in the microbial community.The added biochar can increase the amount of Nitrospirae in the substrate so as to accelerate the conversion and removal of nitrogen.The added dry reed straw can increase the amount of Chloroflexi and Bacteroidetes,and can accelerate the uptake and adsorption of phosphorus.Comparison of cultivated and uncultivated plants showed an increase in Proteobacteria,Nitrospirae and Gemmatimonadetes.The results showed that the addition of biochar and dry reed straw could enhance the removal of total nitrogen and total phosphorus.Based on the above experimental research,in the region of the baiyangdian lake is stable for the implementation of the project scheme,the stable lake add biochar in soil and dry reed stem,by biochar,dry reed stem and soil quality percentage is 1-5:0.5-2:93-98.5 then mixing in soil surface,thickness of 20 to 50 cm,then a water plants grow in the form of cuttings on the mixed substrate layer.To provide technical support for the restoration of aquatic plant growth and water purification in the future.