EXPERIMENTS ON DETENTION,RETENTION AND PURIFYING EFFECTS OF URBAN ROAD RUNOFF BASED ON BIORETENTION

Bioretention is an effective LID(Low Impact Development) practice for stormwater management,while systematic experimental study and applications in China are still not widely carried out.Through small and pilot scale experiments over the last 4 years,long term performance of infiltrating,discharging by regulation and control,and treatment of road runoff was analyzed.It is concluded that permeability declined with increased time of road runoff;Dense,well-developed plant roots and sound particle gradation in the filter media were important for maintaining permeability;Traditional filter media of sand and soil was more effective for runoff retention,peak flow attenuation and reduction,and ponding time was acceptable;Average concentration removal rate of ammonia nitrogen,TN,TP,COD,BOD5 and SS was all above 40%,and the outflow quality of COD,BOD5 should be controlled.Estimation of runoff and pollution load reduction based on experimental results showed that bioretention was an effective source control practice.