Performance of an Anammox UASB reactor at high load and low ambient temperature

• The performance of Anammox under low ambient temperature was investigated.
• The highest NRR (6.6 kg m−3 d−1) was obtained at the temperature lower than 10 °C.
• SBA of high-active Anammox sludge was a successful countermeasure.
• The room-temperature preservation promoted the cold tolerance of the consortia.

The performance of high-loaded anaerobic ammonium oxidation (Anammox) upflow anaerobic sludge blanket (UASB) reactors (R1, R2 and R3) was investigated at low ambient temperatures (28.3–8.5 °C), and measurements of sequential biomass addition (SBA) (R2) and glycine betaine (GB) addition (R3) were carried out as countermeasures for operation under psychrophilic temperature conditions (8.5–13.5 °C). By adding 10 mL highly active Anammox sludge every 2 days, the nitrogen removal rate (NRR) at 9.1 °C increased to 6.6 kg m−3 d−1, almost 20% higher than that of R1 (acclimation). The effect of GB addition on Anammox was varied. Operation using either strategy changed the sludge characteristics. Low biomasses of 12.90 and 9.74 g VSS L−1 were detected in R1 and R2, respectively, after whole investigation, whereas R3 had a biomass of 22.36 g VSS L−1. Adapted sludge had a higher Anammox activity at 15 °C than its non-adapted counterpart. The amount and composition of extracellular polymeric substance (EPS) shifted with different control strategies.