Comparison of the effect of two kinds of ecological grass swales on road runoff purification

The biological packing of aluminum sludge was combined with the stepped ecological grass swale to construct stepped ecological grass swale system, and the effects of stepped ecological grass swale and conventional grass swale on the road runoff purification were compared. The results showed that effect of stepped ecological grass swale on the runoff volume reduction was better than that of conventional grass swale in the two rainfall events, and the reduction rate of runoff volume was 63.04% and 55.21%, respectively. The peak flow was significantly decreased, and the peak time was delayed at least 24-30 min. The stepped ecological grass swale had good water quality control and pollution load reduction effect. The concentration reduction rates of SS, COD_Cr, NH₃-N, TN and TP in the runoff could reach 79.54%, 67.08%, 34.75%, 63.61% and 78.36%, respectively, and the reduction rates of the runoff volume could reach 92.44%, 87.83%, 74.29%, 84.45% and 90.31%, respectively. The effluent water quality was better than that of Class Ⅳ requirement of Environmental Quality Standards for Surface Water (GB 3838-2002). The stepped ecological grass swale could achieve better water quality control and pollution load reduction effect on road runoff, and thus had a good popularization and application value.