Start-up and operational performance of the partial nitrification process in a sequencing batch reactor (SBR) coupled...

Partial nitrification (PN) of ammonia to nitrite is investigated in a lab-scale sequencing batch reactor (SBR) coupled with both a microporous aeration system and a mechanical agitation system at a moderate temperature of (27 ± 1 °C). The SBR has a high actual oxygen transfer efficiency (AOTE) of 2.0% and dynamical efficiency (DE) of 20.0%. Alkalinity consumption declined with the decreasing ratios of HCO₃^- to NH₄⁺-N in the influent from 2.57, 1.96, 1.91 to 1.66, while the pH of the effluent is constantly maintained at 7.5 ± 0.1. The SBR is successfully operated for 195 days at a nitrogen loading rate (NLR) of up to 2.82 kg·m^-3.d^-1, achieving a nitrite accumulation rate (NAR) of over 90%. The high-throughput sequencing shows that the ratio of Nitrosomonas, the dominant species, is up to 29.83%.