The Design And Operation Of The Bioretention With Submerged Area Zone

Bioretention is one of the most representative of low-impact development and non-point source control technology, set the submerged area zone derectly influence the removal of nitrogen, but the reduction of nitrogen polluants has become one of controlling environmental indicators of surface water, it is important to carry out the designation and operation of submerged area zone for application of Bioretention and reduction project of nitrogenous contaminants. This paper investigate the effect on pollutant removal efficiency factors of media height, HRT, the alternation run of wet and dry, rainfall intensity and the submerged area zone height and carbon source, and analyzes the type of microorganisms in bioretention through the high-throughput sequencing. The following studies were carried out:1. The goal is to removal TN, take into account of the removal of TP, NH4+-N, TSS, the experiment analyze the impact of media height and HRT, the result show that the relative optimum operating parameters are media height of 800mm, HRT for 5h, the removal rate of TN, TP, NH4+-N, TSS is 42%,85%,85%,93%.2. The experiment analyze the impact of submerged area zone height and carbon on nitrogen removal, the result show that the removal rate of NH4+-N will decrease with the increase of height, but the removal rate of NH4+-N increase with the increase of submerged area zone height. When submerged area zone height is 450mm, and add newspaper into the submerged area zone, the removal rate of NH4+-N、NO3--N、TN is 73%、68%、50%.3. The experiment explore the influence of removal of nitrogen pollutants in bioretention though different drought length(1 weeks,2 weeks,3 weeks,7 weeks). Through long drought period,the bioretention with submerged area zone had higher removal rate of TN and the removal performance of nitrogen can recovere rapidly. When control the drought length between one week and three weeks, bioretention with submerged area zone but no carbon not only can ensure the removal effect of TN, but also can improve the removal rate of TN from 39% to 56% after recover moisture.4. The experiment simulate different rainfall intensity(large, medium, small) on the effect of contaminant removal. The results show that the bioretention without submerged area zone have better removal rate on TP, NH4+-N than that with submerged area,but for TSS,the removal rate is lower.The bioretention with submerged area zone and carbon source have higher removal rate on TN and NO3--N.5. The media of bioretention in upper layer (-50mm～-300mm) and low layer (-400～-650mm) were analysised by high throughput sequencing. The results is that the dominant bacteria in upper filler is mainly the heterotrophic aerobic bacteria with capable of oxidation,it can decompose of organic matter. According to the analysis of the nitrogen with depth, the removal of NO3--N mainly occurred in the lower filler.The results of this experiment can guide the design and operation of bioretention, especially the design of ubmerged area zone.