[Performance and Microbial Characteristics of Ammonium-limited and Nitrite-limited ANAMMOX Systems].

The performance and microbial characteristics of ammonium-limited and nitrite-limited ANAMMOX reactors were studied in two continuously stirred tank reactors. The influent TN concentrations were controlled below 50 mg·L. The hydraulic retention time and water temperature were maintained at 2.0 h and 20℃, respectively. Results showed that though both ANAMMOX reactors demonstrated similar TN removal loading rates[0.45-0.5 kg·(m·d)] and TN removal efficiencies (around 70%), the ΔNO/ΔNH ratio of the ammonium-limited ANAMMOX reactor showed a faster upward trend. Batch tests and high-throughput sequencing results indicated that the ammonium-limited ANAMMOX reactor had more significant functional and population heterogeneity than the nitrite-limited ANAMMOX reactor. was the predominant ANAMMOX bacteria in both reactors. The relative abundance of in large granules (53.9%) was significantly higher than that in flocs (19.1%) under the ammonium-limited conditions, whereas only a small difference in relative abundance of was observed between the granules (28.1%) and flocs (21.3%) in the nitrite-limited ANAMMOX reactor. -like NOB were detected in both ANAMMOX reactors, which primarily inhabited flocs, seemingly driven by the availability of oxygen. Moreover, the ammonium-limited (i.e., excess nitrite) conditions seemingly favored the growth of . Building upon these results, a control strategy for optimal operation of the ammonium-limited ANAMMOX reactor was proposed based on selective floc discharge.