| In order to investigate shortcut nitrification, an intermittent-aeration SBR was employed to treat the domestic wastewater containing low concentration of NH+4. The results shows that under the SRTs of 10, 5, 2.5 and 1.25 d, NO-2 produced in effluent were built up to 18, 19, 14 and 5 mg/L, respectively, with accumulation ratio of 73%, 85%, 91% and 78% respectively. As to the continuous-aeration SBR, however, the NO-2 accumulation ratios were only 14%, 21%, 31% and 34%. In addition, the corresponding removals of NH+4 in the intermittent-aeration SBR were maintained at a comparable level in contrast to those for the continuous-aeration SBR, i.e., 97%, 95%, 76% and 39% vs 92%, 97%, 71% and 47%. By exploring the growth kinetics of nitrifiers, ammonia-oxidizing bacteria (AOB) in the intermittent-aeration system was capable of increasing its biomass in the reactor by an elevation in growth yield (YAOB), which as a result compensated the decreased specific substrate utilization rate at low DO level and further led to the unchanged μm value and NH+4 oxidation rate. On the contrary, nitrite-oxidizin bacteria (NOB) was lack of the function of compensability, and it hence lowered the μm value and NO-2 oxidation rate, and therefore resulted in an accumulation of NO-2 in the effluent. |
