Study On The Effectiveness Of Pyrite Modified Bioretention System To Treat Nitrogen And Phosphorus From Stormwater Runoff With Limitation Of Carbon Source

With the popularization of municipal drainage networks and urban sewage treatment plants,the impact of urban stormwater runoff pollution control on the water environment has gradually become more prominent.Bioretention system is a common method of urban rainfall and runoff pollution control.Because it can effectively control pollutants in urban rainfall and runoff,it has attracted long-term attention from scholars and entered engineering application practice.However,the denitrification efficiency of the traditional bioretention system in the treatment of stormwater runoff is limited by the few of carbon source in the runoff,which is difficult to further improve.In this study,pyrite was used as a filler,combined with the submerged zone,to improve the traditional bioretention system.In the natural environment,the actual operation effect of the bioretention experimental device in the initial operation stage,the operation stage without organic carbon source inflow,and the operation stage of low organic carbon source inflow was monitored.The water quality of the substrate layer in a single cycle was tracked many times.The microbial community was analysis in the substrate layer under different working conditions.The main conclusions are as follows:(1)The feasibility of removing nitrogen and phosphorus pollutants in the natural environment of pyrite improved biological retention system process was explored.Among them: during the operation stage without organic carbon source,the total nitrogen and The average removal rate of total phosphorus was 86% and 81%respectively;the average removal rate of total nitrogen and total phosphorus of the zeolite bioretention system facilities were 32% and 44%;in the operation stage of the low organic carbon source influent of 20 mg / L,sulfur The average removal rate of total nitrogen and total phosphorus in the iron ore biological retention system facilities was92% and 86%,respectively;the average removal rate of total nitrogen and total phosphorus in the zeolite biological retention system facilities was 63% and 35%,respectively.The results show that pyrite as a matrix filler can significantly improve the nitrogen and phosphorus removal efficiency of the biological retention system under the condition of limited carbon source for stormwater runoff.(2)Monitoring of the water quality of the matrix layer over multiple cycles found that ammonia nitrogen was adsorbed within 2 hours of entering the experimental device.In the case of scarce carbon source,the pyrite bioretention system can achieve more than 80% of nitrogen removal effect at around 72h;in the case of limited carbon source,the pyrite bioretention system can be from 12 h to 24 h Most of the denitrification and denitrification are completed in between.The bioretention system of pyrite as a filler will inhibit enzyme activity at low temperatures and produce a large amount of nitrite nitrogen accumulation,which may have a potential impact on the water environment.(3)The average iron concentration in the effluent of the pyrite bioretention system throughout the study was 0.51 mg / L with large fluctuations;the average sulphate concentration in the effluent was 106.97 mg / L.These by-products have a certain impact on the environment.The analysis shows that most of the sulfates come from the oxidation of pyrite,and the acidity produced at the same time leads to a low p H value in the effluent of the pyrite plant.(4)The change of the microbial community in the substrate layer from the inflow stage without organic carbon source to the inflow stage with low organic carbon source showed that the relative abundance of Thiobacillus,which is a symbolic species of sulfur autotrophic denitrification,ranges from 1.6% to 2.6%.It shows that pyrite is used as a filler in the bioretention system,and sulfur autotrophic denitrification can exist in it to produce a certain effect without being affected by a certain amount of organic carbon source.At the same time,the addition of pyrite can significantly improve the denitrification and denitrification capacity of the biolretention system.