Effect of nitrite concentration on the growth and microbial diversity of anaerobic ammonia oxidation (anammox) sludge

ABSTRACT The effect of influent NO 2 – –N concentration on the growth and microbial diversity of anaerobic ammonia oxidation (anammox) sludge is unclear. In this study, influent NO 2 – –N concentrations of 25.53, 51.63, and 102.99 mg/L were used to study the effect of the anammox sludge growth and microbial diversity in an up-flow anaerobic sludge blanket reactor. Influent concentration had a substantial influence on anammox microorganisms. When the NO 2 – –N concentration was 51.63 mg/L, the nitrogen removal efficiency was 12.96% less than that at low concentration and 8.50% higher than that at high concentration. However, the specific anammox activity, total solids, and carbon sequestration were at maximum levels. Therefore, this concentration was most suitable for the growth of anammox microorganisms, with a growth rate of 1.31 g-VSS/g-N, which was 15 times higher than the theoretical growth rate, and Candidatus Kuenenia comprising 75.11% of the dominant bacteria in the reactor.