Title: Unconventional microbial mechanisms for the key factors influencing inorganic nitrogen removal in stormwater bioretention columns
Authors: Liuqin Huang, Junyue Luo, Linxin Li, Hongchen Jiang*, Xiaoxi Sun, Jian Yang, Weiyu She, Wen Liu, Liqing Li*, Allen P. Davis
Source: Water Research
DOI: 10.1016/j.watres.2021.117895
Available online: 25 November 2021
Link: https://www.sciencedirect.com/science/article/pii/S0043135421010897?via%3Dihub
Abstract:
Bioretention systems are environmentally friendly measures to control the amount of water and pollutants in urban stormwater runoff, and their treatment performance for inorganic N strongly depends on various microbial processes. However, microbial responses to variations of N mass reduction in bioretention systems are complex and poorly understood, which is not conducive to management designs. In the present study, a series of bioretention columns were established to monitor their fate performance for inorganic N (NH4+ and NO3-) by using different configurations and by dosing with simulated stormwater events. The results showed that NH4+ was efficiently oxidized to NO3-, mainly by ammonia- and nitrite-oxidizing bacteria in the oxic media, regardless of the configurations of the bioretention systems or stormwater conditions. In contrast, NO3- removal pathways varied greatly in different columns. The presence of vegetation efficiently improved NO3- mass reduction through root assimilation and enhancement of microbial NO3- reduction in the rhizosphere. The construction of an organic-rich saturation zone can make the redox potential so low that heterotrophic denitrification cannot occur, so as to ensure high NO3- mass reduction mainly via stimulating chemolithotrophic NO3- reduction coupled with oxidation of reductive sulfur compounds derived from the bio-reduction of sulfate. In contrast, in the organic-poor saturation zone, multiple oligotrophic NO3- reduction pathways may be responsible for the high NO3- mass reduction. These findings highlight the necessity of considering the variation of N bio-transformation pathways for inorganic N removal in the configuration of bioretention systems.
