AbstractThis study investigates the pollutant removal performance and cleaning characteristics of six sand-based bioretention systems. The sand-based bioretention systems used fine sand and peat soil as the primary substrates mixed with volcanic rock, green zeolite, coal slag, vermiculite, and perlite as additives, and a system without additives was used as the control. The influence of the influent concentration and rainfall intensity on the pollutant removal performance was investigated, and the cleaning characteristics of the six systems were explored using the total suspended solids (TSS), total phosphorus (TP), ammonium nitrogen (NH4+-N), total nitrogen (TN), and the chemical oxygen demand (COD) as pollutant indicators. The results showed that (1) the influent concentration had a more obvious influence on the TP, NH4+-N, and COD, which were primarily removed by the adsorption of fillers, (2) high intensity rainfall was more detrimental for the removal of NH4+-N and TN than for the other pollutants, but the addition of media with a good nitrogen removal performance, such as green zeolite and vermiculite, mitigated this detrimental influence, and (3) dissolved pollutants such as TP, NH4+-N, TN, and COD retained in the sand-based bioretention systems all had the potential to be flushed out during next rainfall event, and the ease of being flushed out varied among the different fillers.

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