Microbial Heterotrophic Nitrification-Aerobic Denitrification Dominates Simultaneous Removal of Aniline and Ammonium in Aquatic Ecosystems

A heterotrophic nitrification-aerobic denitrification (HN-AD) mixed culture was established as a simulated aquatic ecosystem to investigate the simultaneous removal of aniline and ammonium, as well as the succession of bacterial community. Aniline and ammonium were found to be simultaneously transformed, with maximum removal efficiencies of 99.98% and 89.87%, respectively. The presence of aniline at lower concentrations (0 to 100 mg/L) slightly inhibited ammonium oxidation, whereas further increasing the aniline concentration (from 100 to 500 mg/L) yielded an apparent enhancement effect, increasing the ammonium-N removal rate from 0.33 to 1.26 mg/L/day. In contrast, ammonium-N concentrations of 100 mg/L were able to facilitate aniline removal. Ammonium was the preferred nitrogen source for aniline removal when compared with nitrification metabolites such as nitrate or nitrite. The analysis of microbial community succession using high-throughput sequencing revealed that the microbial diversity generally decreased throughout the aniline and ammonium removal process. Proteobacteria is observed to increase at the climax stage, and the average relative abundances of Pseudomonas, Massilia, and Bacillus were highest at the climax stage and were positively related to the removal rate of aniline and ammonium-N. Surprisingly, the abundance of these microbes at the end stage was almost equal to that observed at the initial stage. This study demonstrated that polluted aquatic ecosystems hold potential for simultaneous removal of pollutants (hazardous organic carbon and ammonium), and have excellent self-rehabilitation abilities.