Effect of decreasing temperature on the performance and extracellular polymer substance of anaerobic ammonia oxidation sludge

In this study, a long term dynamic change in anammox reaction in response to the gradient decreased and recovered temperature (33→25→20→15→10→22℃) was evaluated in a sequencing batch reactor (SBR) running over 360days; both the specific anammox activity (SAA) and extracellular polymers (EPS) contents were assessed. Results showed that anaerobic ammonia oxidation reaction in the SBR remained stable and efficient at 20~33℃; the total nitrogen removal load was 0.4gN/(L·d) and the SAA was over 0.32gN/(gVSS·d). The temperature of 10℃ was the turning point for the anammox bacteria metabolic activity. At 10℃, anammox treatment capacity reduced significantly, with the SAA being decreased by 91% when compared with that at 33℃. However, anammox activity could be recovered to 0.24gN/(gVSS·d) at 22℃. The apparent activation energy (Ea) values was 68.4kJ/mol at 10~33℃ and 152.9kJ/mol at 10~20℃. In the range of 15~33℃, the EPS content of the anammox biomass increased with decreasing temperature; however, after temperature decreased to 10℃, the EPS content dropped significantly, and anammox sludge broke up into smaller flocs, leading to the loss of biomass from the bioreactor. © 2016, Editorial Board of China Environmental Science. All right reserved.