WANG Qin-yi, WU Qiong, NI Jian-hua, LIAN Xiao-ke, ZOU Gao-ju, YUAN Ying, XIAO Hong-jun, CHEN Yao
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To achieve efficient resource utilization of construction waste residue (CWR) and address the issue of effluent pH reduction during the nitrogen removal process in a pyrite-enhanced bioretention system, a bioretention system was constructed using a composite medium composed of CWR and pyrite. This study investigated the impacts of varying dosing of CWR and different compositing approaches for the mixture medium on pollutant removal efficiency by bioretention system. Moreover, an optimal strategy for composite media was determined by analyzing microbial community composition and evaluating by-products control effects. The results demonstrated that the addition of 40% (V/V) CWR into the traditional medium resulted in an enhancement of 8.70% and 9.69% in the removal rates of NH4 +-N and TP, respectively. Nevertheless, due to alkaline leaching stress, there was a decrease of 5.27% in COD removal rate and emergence of NO2 --N accumulation phenomenon. The integration of media significantly mitigated the alkaline stress effect caused by CWR, leveraged the strong adsorption capacity of CWR for nitrogen and phosphorus, and enhanced denitrification through the use of pyrite as an electron donor for autotrophic denitrification. Consequently, this strategy not only increased the α-diversity of the microbial community but also elevated the relative abundance of nitrifying genera (e.g., Nitrospira) and denitrifying genera (e.g., Denitratisoma and Bacilli), while simultaneously inhibiting the growth of Thiobacillus and Thauera. As a result, the system's pollution removal efficiency was significantly improved, effectively addressing the issue of NO2 --N accumulation in the effluent and achieving better control over effluent pH、TFe and SO4 2- byproducts. Particularly, incorporating 40% (V/V) CWR in the planting layer along with 20% (V/V) in the submerged layer of bioretention system achieved superior decontamination performance with respective removal rates for COD、TP、NH4 +-N、NO3 --N and TN being 84.49%、96.94%、91.83%、87.11% and 82.13% respectively. Additionally, all concentration levels for by-products remained below permissible limits.