This study compared two anammox sequencing batch reactors (SBR) for one year. SBR was kept at 30 °C while temperature in SBR was decreased step-wise from 30 °C to 20 °C and 15 °C followed by over 140 days at 12.5 °C and 10 °C. High retention of anammox bacteria (AnAOB) and minimization of competition with AnAOB were key. 5-L anoxic reactors with the same inoculum were fed synthetic influent containing 25.9 mg NH-N/L and 34.1 mg NO-N/L (no COD). Specific ammonium removal rates continuously increased in SBR, reaching 785 mg NH-N/gVSS/d, and were maintained in SBR, reaching 82.2 and 91.8 mg NH-N/gVSS/d at 12.5 and 10 °C respectively. AnAOB enrichment (increasing hzsA and 16S rDNA gene concentrations) and adaptation (shift from Ca. Brocadia to Ca. Kuenenia in SBR) contributed to these high rates. Rapidly settling granules developed, with average diameters of 1.2 (SBR) and 1.6 mm (SBR). Results reinforce the potential of anammox for mainstream applications.
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