Control Of Bioretention On Urban Rainfall Runoff

The urban development over recent decades has increased rainfall flow,urban flooding and non-point source pollution.Bioretention systems have been widely researched to address hydrology and water quality issues,however,the influencing factors of bioretention to purify water quality and regulate hydrology are still unclear.This study evaluated the reulatory effectiveness of different packings（original soil,fine sand,zeolite）,field bioretention systems with ryegrass and without ryegrass.The bioretentions were subjected to a series of simulated rainfall events using synthetic stormwater by orthogonal experiment.The unplanted bioretentions with original soil,zeolite and sand as fillers had obvious effects on the removal of COD,NH₃-N and TP.The average removal rates of COD,NH₃-N,TP and NO₃-N were 70.2%,70.2%,32.8%and 13.4%in the original soil bioretention,34.1%,45.9%,48.4%and 5.3%in zeolite bioretention,and 63.8%,62.1%,44.4%,7.6%in the fine sand bioretention.The removal efficiency of three kinds of bioretention ponds in the absence of plants was as follows:original soil bioretention>sand bioretention>zeolite bioretention.The removal efficiency of pollutants on original soil bioretention,zeolite bioretention and sand bioretention had changed after planted.The plants weakened the removal efficiency of COD and NH₃-N in the original soil bioretention,with an average removal rate of 25.9%and 20.3%respectively.However,plants had little effect on the removal of pollutants in the fine sand bioretention.Under different influent conditions,the average reduction efficiency of the original soil bioretention,zeolite bioretention and fine sand bioretention to the peak flow is 25.63%,18.22%and 22.30%respectively,and the average reduction rate to the total runoff is 34.52%,28.29%and 28.03%respectively.The control efficiency of the three groups of bioretentions to the rainfall runoff is as follows:original soil bioretention>fine sand bioretention>zeolite bioretention.The plants generally reduced the ability of bioretentions to control rainfall runoff...