Research On Filling In Biological Retention Facility Based On Initial Runoff Rainwater Of Road

With the development of urbanization,the nitrogen and phosphorus pollutants contained in rainwater runoff have become the main reason for the eutrophication of receiving waters such as rivers and lakes.As one of the facilities of the sponge city,the biological retention facility can not only effectively reduce runoff,but also remove pollutants from rainwater runoff.However,many studies have shown that biological retention facilities with submerged areas can improve the nitrate nitrogen in rainwater,but the removal effect of total phosphorus and ammonia nitrogen is not optimistic.In order to solve this problem,In this study,the initial rainwater runoff quality of local roads in Kunming was taken as the research object to improve the filling layer of biological retention facilities.The main research results are as follows:?1?The results of the nitrogen and phosphorus pollutants tested on the initial rainwater runoff on the campus road of Kunming University of Science and Technology showed that the concentrations of TP and NH₄⁺-N exceeded the Class?water quality standards in the Environmental Quality Standards for Surface Water,The final determination of the concentration of nitrogen and phosphorus pollutants in the initial rainwater runoff in the laboratory simulation of Kunming was TP:1mg/L;NH₄⁺-N:5mg/L;NO₃^--N:3mg/L.?2?The modified filler was used in the isothermal adsorption and desorption test of total phosphorus and ammonia nitrogen.The results showed that:steel slag has the best effect of adsorbing total phosphorus;Rice husk char has the best effect of adsorbing ammonia nitrogen.The desorption rate of steel slag and rice husk char to phosphorus and ammonia nitrogen is not high and has certain stability.The fitting results with Langmuir equation and Freundlich equation show that:the adsorption of total phosphorus by steel slag is more in line with physical adsorption and chemical adsorption in various situations;The adsorption of ammonia nitrogen by rice husk char is also more in line with the physical and chemical adsorption of Freundlich equation.?3?Through the experiment of the optimal addition amount of filler in the filler layer,the conclusion is drawn:85%sand,5%native red loam,10%steel slag,and rice husk carbon combined filler are the best addition ratios for the filler layer of the improved biological retention facility in Kunming.The removal effect of TP and NH₄⁺-N and the effluent concentration of the bio-retention facility under this addition ratio meet the requirements of the"Technical Guidelines for Construction of Sponge City in Kunming",and the permeability coefficient and p H also meet the relevant requirements.The analysis of the experimental data by orthogonal partial least squares found that the addition of steel slag and rice husk char had a greater impact on the removal of TP and NH₄⁺-N;the addition of red loam had a greater impact on the permeability coefficient of the biological retention facility.?4?Carry out experiments on different influent amount and different influent pollutant concentration in the improved biological retention facility of combined filler,and compare it with the traditional biological retention facility.The results show that the removal effect of TP and NO₃^--N decreases with the increase of influent volume;however,different influent volume is not a significant influencing factor for the removal of NH₄⁺-N,NH₄⁺-N has a certain stability under different influent volume Sex and anti-interference.Test results of different influent pollutant concentrations show that different influent pollutant concentrations have certain effects on TP,NH₄⁺-N and NO₃^--N,and the concentrations of TP and NH₄⁺-N increase with the influent pollutant concentration While increasing.However,the removal of NO₃^--N by different influent pollutant concentrations decreases as the influent pollutant concentration increases.?5?By comparing the bioretention facility improved by the combined filler with the traditional sand-only bioretention facility,the results show that:The removal rate of TP and NH₄⁺-N in the improved biological retention facility is 20%?40%higher than that of the traditional biological retention facility under different influent conditions.It fully shows that the improved biological retention facility has obvious effect on the removal and promotion of TP and NH₄⁺-N.For the removal effect of NO₃^--N,the improved biological retention facility is not much different from the traditional biological retention facility.