Research On The Removal Of Pollutants In Rainwater Runoff By Biological Retention Technology

Rainwater runoff has become an important source of surface water pollution and has greatly contributed to urban surface water pollution and water environment deterioration.Bioretention is a low impact development(LID)measure in urban stormwater management.It has been demonstrated that bioretention technology is an effective measure to remove pollutants in storm runoff.In recent years,bioretention has been widely applied in the prevention and control of urban runoff pollution.Based on the characteristics of the biological retention pool in Licang District of Qingdao,this paper selects the heavy metals(Cu?Pb?Zn?Cr),polycyclic aromatic hydrocarbons and nitrogen and phosphorus indexes which are common in heavy rainwater runoff and pollutes heavily and conducts on-site sampling during the whole rainfall in 2017,the time and spatial distribution characteristics of pollutants in the runoff of Licang District were clarified.Based on the field monitoring data,the quantitative analysis of pollutants in the runoff from which biological retention was carried out was carried out.The results showed that:(1)There is generally higher pollutant pollution in the runoff of rainwater,and different degrees of pollution in different runoffs.The overall concentration of nutrient elements in residential runoff is much higher than that of road runoff.The degree of heavy metal pollutants in runoff is much higher than that of residential runoff.There is a certain degree of polycyclic aromatic hydrocarbons pollution in road runoff and runoff.(2)Various types of bioretention cells have a certain removal effect on the existence of various pollutants in runoff.For TN,the removal efficiency of each sampling point is between 21%-82%;for TP,the removal effect of each sampling point is between 17%-76%.Different types of biological retention pool on the overall removal of heavy metals in the range of distribution between 14%-71%.The removal efficiencies of PAHs in different types of bioretention tanks ranged from 21.88% to76.56%.(3)The typical feature of nutrient elements and metal distribution is that the surface accumulates significantly,the concentration decreases as the depth increases,and it usually approaches the background value.The distribution of PAHs varies with depth,but the cumulative range of PAHs is limited to above 10 ~ 40 cm.The presence of plants,the depth and type of filter media,the presence of saturated zones,and the land use around the bioretention pool in the bioretention pool all have some effect on the removal of contaminants from the stormwater runoff in the bioretention facility.Contaminants present in the upper layers of the soil have the potential for a potential contamination disturbance that does not necessarily prevent downward flow even at low surface contentsbecause the deeper layers may have less retention and the surface Specific soil amendments may help prevent this problem.