Water Resources and Power

In order to improve the nitrogen removal effect of the bioretention system and promote the construction of sponge cities in the loess distribution area, removal effect of nitrogen in rain runoff by the loess media-improved bioretention systems were studied. Setting five kinds of fillers including T(loess), TS(60% loess + 40% sand), TSF(42% loess + 28% sand + 30% fly ash), TSG(42% loess + 28% sand + 30% steel slag), TSC(42% loess + 28% sand + 30% red mud), physical model test of soil column in laboratory was used to study their total volume control and nitrogen removal effects on simulated rain-runoff. The results show that adding sand, steel slag and red mud can improve the total runoff control rates of the system, and TS system was the highest, and increased with the increase of operation time, up to 95.79 %; Adding sand, fly ash and red mud in loess, the removal rates of NH⁺_4-N were not significantly influenced, and the removal rates were high and all were above 80%; But after adding steel slag, the removal rate decreased significantly, and the average removal rate was only 41.18 %; Adding steel slag decreased the removal of NO~-₃-N, the average removal rate was only 32.06 %; While adding red mud the removal rate was the highest, and the average removal rate was 91.42 %.