Microbial community and nitrogen transformation pathway in bioretention system for stormwater treatment in response to formulated soil medium

Bioretention system has been commonly recognized as an emerging management method to control urban rainwater runoff. However, nitrogen conversion mechanisms in bioretention system in response to for-mulated soil medium remains unknown. In this work, five bioretention columns with different formulated soil medium were established, and results indicated that all bioretention columns achieved high NH4+-N removal rate, but exhibited significantly different NO3--N removal performance. High-throughput se-quencing results suggested that nitrification might be achieved by heterotrophic nitrifying bacteria, while Pseudomonas and Rubellimicrobium may be the main denitrifying bacteria, which served as anaerobic and aerobic denitrifier, respectively. Heterotrophic nitrification-anaerobic/aerobic denitrification may the mi-crobial pathways to realize effective nitrogen removal performance in these bioretention systems. Bioretention system with moderate silt content (NC, 10%) displayed higher abundant potential denitrifier, leading to better nitrogen removal performance. Besides, soil adsorption played an important role in ni-trogen removal, particularly when activated carbon was added. This work could provide guidance of for-mulated soil medium optimization for the application of bioretention systems. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the nitrogen conversion mechanisms in bioretention systems with different formulated soil medium. The results revealed that heterotrophic nitrification and anaerobic/aerobic denitrification were the microbial pathways for effective nitrogen removal. Bioretention systems with moderate silt content showed higher potential denitrifier abundance and better nitrogen removal performance. Soil adsorption also played a significant role in nitrogen removal, especially when activated carbon was added.