Behaviors of Biomass and Kinetic Parameter for Nitrifying Species in A2O Process at Different Sludge Retention Time

The effect of sludge retention time (SRT) on biomass, kinetic parameters, and stoichiometric parameters of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in anaerobic/anoxic/oxic (A2O) process were explored in this study. The results showed that the growth rate constants were 1.52, 1.22, and 0.85 day−1, respectively, for AOB, those were 1.59, 1.19, and 0.87 day−1, respectively, for NOB when SRT was 20, 10, and 5 days. The lysis rate constants of AOB and NOB were 0.14 and 0.09 day−1, respectively. The yield coefficients were 0.23 and 0.22, respectively, for AOB and NOB. They did not change with SRT obviously. The biomass of AOB was 50.94, 26.35, and 14.68 mg L−1, respectively, and the biomass of NOB was 116.77, 60.00, and 44.25 mg L−1, respectively, at SRT of 20, 10, and 5 days. When SRT diminished from 20 to 5 days, the biomass of AOB and NOB diminished by 36.26 and 75.52 mg L−1, respectively. The removal efficiency of NH4 +–N diminished by 68.9 %. The removal efficiency of total nitrogen diminished by 42.9 %.