Comparative effects of ammonium nitrogen on perchlorate degradation performance under heterotrophic condition with...

Perchlorate (ClO₄^-) mainly exists in the form of ammonium perchlorate in industrial production. However, the degradation mechanisms of different concentrations of ammonium nitrogen (NH₄⁺-N) and ClO₄^- mixed pollutants in the environment are not well understood. This study aims to explore the potential of different types of carbon sources for ClO₄^- and NH₄⁺-N biodegradation. Experimental results showed that the concentration and type of carbon sources are decisive to simultaneous removal of NH₄⁺-N and ClO₄^-. Under condition of C(COD)/C(ClO₄^-) ratio of 21.15 ± 4.40, the simultaneously removal efficiency of ClO₄^- and NH₄⁺-N in acetate (Ace) was relatively higher than that in methanol (Met). C(NH₄⁺-N)/C(ClO₄^-) ratio of 9.66 ± 0.51 and C(COD)/C(ClO₄^-) ratio of 2.51 ± 0.87 promoted ClO₄^- reduction in glucose-C (Glu-C). However, high concentration of Glu could cause pH decrease (from 7.57 to 4.59), thereby inhibiting ClO₄^- reduction. High-throughput sequencing results indicated that Proteobacteria and Bacteroidetes have made a major contribution to the simultaneous removal of NH₄⁺-N and ClO₄^-. They are two representative bacterial phyla for participating in both ClO₄^- reduction and denitrification. Notably, the abundance of main ClO₄^- degrading bacteria (such as Proteobacteria, Chloroflexi, and Firmicutes) significantly increased by 528.57 % in Glu-C. It can be inferred that the concentration of carbon source and NH₄⁺-N were the most important factors determining the removal efficiency of ClO₄^- by influencing changes in the core microbial community. This study will provide new techniques and mechanistic insights for the simultaneous removal of mixed ClO₄^- and nitrogen pollutants, which can also provide theoretical support for innovation in future biological treatment processes.