Effect of hydraulic retention time on microbial community structure and nitrogen metabolism in anaerobic-anoxic-oxic process.

Microorganisms in wastewater treatment play a critical role in the degradation and removal of organic wastes and foreign contaminants, but they are vulnerable to the effects of operational working conditions. We investigated the changes in microbial community structure and abundance while the A2/O process was operated at four different hydraulic retention durations using 16S rRNA gene sequencing. The results showed that microbial abundance and diversity increased with hydraulic retention time (HRT), and the genus level was more significantly affected by HRT than the phylum level. The dominant phylum and genus were Proteobacteria, Bacteroidetes with norank_f__AKYH767, Saprospiraceae, etc. The bacteria under the level of dominant phylum and dominant genus affected by HRT each had certain antagonistic effects, and the anaerobic pool microorganisms had the highest abundance and diversity. In nitrogen metabolism, HRT significantly affects the abundance of enzymes and functional genes. Enzymes involved in denitrification (44%) and denitrification functional genes (30.68%) have the highest abundance; HRT affects nitrogen removal efficiency by influencing the abundance of denitrification functional genes. The abundance of denitrification functional genes is the highest at 17 h; the increase of HRT is beneficial to denitrification, but has little effect on nitrification. The results provide a reference for understanding microbial and nitrogen metabolism influenced by HRT. [ABSTRACT FROM AUTHOR]