Startup of a large height-diameter ratio bioreactor by alternate feeding: performance of partial nitrification and enrichment of ammonia-oxidizing bacteria (AOB)

In order to solve the complicated control of dissolved oxygen (DO) for partial nitrification in bioreactors treating high ${\mathrm{NH}}_4^{+}-N$ wastewater, a large height-diameter ratio anammox pre-reactor system was developed. And in this reactor, ${\mathrm{NO}}_2^{-}-N$ accumulation rate can reach 85.76% by alternate feeding with high ${\mathrm{NH}}_4^{+}-N$ wastewater (150 mg ${\mathrm{NH}}_4^{+}-N/L$) and low ${\mathrm{NH}}_4^{+}-N$ wastewater (50 mg c) with low DO (0.19 mg/L-0.62 mg/L). Based on 16S rRNA identification technology, it was found that Nitrosomonas had a significant effect on ${\mathrm{NH}}_4^{+}-N$ oxidization in this study. And when the reactor treated higher concentration wastewater (250 mg ${\mathrm{NH}}_4^{+}-N/L$), the growth rate of Nitrosomonas was higher than that of Nitrospira (nitrite-oxidizing bacteria, NOB), which was conducive to improving the ${\mathrm{NO}}_2^{-}-N$ accumulation rate and realizing partial nitrification stably. It was also found that the material exchange frequency of the microbial flora during alternate feeding with different ${\mathrm{NH}}_4^{+}-N$ concentration wastewaters was higher than that during feeding with higher ${\mathrm{NH}}_4^{+}-N$ concentration wastewater (250 mg/L) by Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolism pathways analysis. This study can provide valuable insights and lay the foundation for building anammox pre-reactors.