Coal gangue modified bioretention system for runoff pollutants removal and the biological characteristics.

In this study, coal gangue (CG) was applied as media in bioretention system to remove runoff pollutant. CG modified bioretention systems show good removal efficiency towards runoff pollutant due to the high adsorption capacity of CG. The removal of total phosphorus (TP), total nitrogen (TN), ammonia (NH 4 +-N) and chemical oxygen demand (COD) by CG modified bioretention systems was influenced by diverse rainfall conditions including rainfall concentration, recurrence period and drying period, and their removal rate ranged 94–99%, 30–70%, 83–97% and 33–86%, respectively. The effluent concentration of Zn, Pb and Cu was as low as 3.14–10.99 μg/L, 0.66–2.56 μg/L and 0.60–3.15 μg/L, respectively. In addition, CG could promote the plant heavy metal uptake and thus decrease their accumulation in soil to a certain extent. Meanwhile, Malondialdehyde (MDA) content and peroxidases (POD) activities of plants in CG modified bioretention were lower than that in tradition bioretention, indicating that CG could help plants recovery and lessened the oxidative stress for the negative impact of high heavy metals accumulation. CG-based media alleviated the inhibitory effect of rainwater runoff pollutant accumulation (especially heavy metals) on microbial diversity and the enhancement of the dominant bacteria (such as Proteobacteria and Bacteroidota) could conduce the nutrients removal in the bioretention systems. In overall, this study demonstrated that the CG modified bioretention systems show an excellent removal performance combine with biological effects. [Display omitted] • The CG modified bioretention improves the removal of nutrients and heavy metals. • Rainfall recurrence and drying periods could influence the removal of pollutants. • Bioretention with CG-based media and CG filter show best removal efficiency. • CG improves heavy metal uptake in plants and relieve the stress of heavy metals. • CG promotes microbial diversity and enhances the dominant bacteria in bioretention. [ABSTRACT FROM AUTHOR]