Biodiversity and quantification of functional bacteria in completely autotrophic nitrogen-removal over nitrite (CANON) process

The research was conducted to investigate the microbial diversity and population with the different concentration of NH4+–N in a biofilm reactor filled with volcanic filter for completely autotrophic nitrogen-removal over nitrite (CANON) process. The reactor had an excellent performance with the decreasing of NH4+–N concentration from 400 to 200 mg L−1 while NH4+–N removal loading reduced at the NH4+–N concentration of 100 mg L−1. Biodiversity analysis indicated that Nitrosomonas related aerobic ammonia oxidizing bacteria (AOB) and Planctomycetales-like anaerobic ammonia oxidizing (anammox) bacteria were dominant functional bacteria. Despite the different influent NH4+–N concentration, anammox bacteria had a low and stable biodiversity, which was not the same to AOB. With the concentration reduction of influent NH4+–N, the estimates of total bacteria population ranged between 2.29 × 1011 and 1.44 × 1012 copies mg−1 total DNA, and the quantity of AOB decreased while anammox bacteria kept stable. The population of Nitrospira increased and little Nitrobacter was detected during the experiment.