Influence of temperature on anammox reaction and microbial diversity in a bio-carriers reactor under mainstream conditions

Abstract

The hypersensitive with seasonal temperature fluctuation of anaerobic ammonium-oxidizing bacteria has usually limited the actual implementation of the anammox process. Thus far, temperature influences on anammox reaction and microbial consortium structure under mainstream conditions was not thoroughly studied. In this study, hydrazine dehydrogenase (HDH) activity and specific activity of anammox bacteria were studied in a 10 L bench scale Continuous Anammox Bio-carrier Reactor (CABR) at nitrogen loading rates of 0.2–0.4 kg N/m3 ⋅ d and a temperature range from 18 °C to 35 °C. At 35 °C, CABR achieved nitrogen removal efficiency above 94% and the nitrogen removal rate of 0.25–0.3 kg N/m3 ⋅ d. When the temperature decreased to 18 °C, the nitrogen removal efficiency and nitrogen removal rate reduced 62.2% and 0.1 kg N/m3 ⋅ d, respectively due to 3.5-folds reduced HDH activity. At 10 °C, specific activity of anammox bacteria declined to 0.02 g N/gVSS ⋅ d, which was 1/7 of that at 35 °C. Anammox reaction could recover when temperature increased to 23 °C with NRE of 85%. It revealed that temperature directly impacted HDH activity was a key parameter influencing anammox metabolism. Activation energy (Ea) calculated for specific activity of anammox bacteria at 10–18 °C and 10–35 °C were approximately 120 kJ/mol and 57 kJ/mol, respectively. Also, 16S rDNA sequencing results revealed that C. Jettenia well adapted to temperature-varying conditions, which implied the CABR could be a favorable process for anammox applications with seasonal temperature change in sub-tropical and tropical climate regions.