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Temperature dependence of nitrogen removal activity by anammox bacteria enriched at low temperatures
- Park, Giri, Takekawa, Masashi, Soda, Satoshi, Ike, Michihiko, Furukawa, Kenji
- Journal of bioscience and bioengineering 2017 v.123 no.4 pp. 505-511
- activated sludge, activation energy, ambient temperature, anaerobic ammonium oxidation, cold zones, freshwater, nitrifying bacteria, nitrogen, Japan
- The anaerobic ammonium oxidation (anammox) process, which is applicable at ambient temperature, is necessary to develop more versatile nitrogen removal technologies. In this study, two anammox reactors, Low-R1 and Low-R2 inoculated with activated sludge respectively in Kumamoto and Hokkaido, Japan, achieved nitrogen removal rates (NRRs) of 1.5 kg-N/m³/day at 20°C. The specific anammox activity (SAA) of the Low-R1 and Low-R2 sludge samples had peaks, respectively, of 2.8±0.3 mg-N/g-VSS/h at 25°C and 4.2±0.3 mg-N/g-VSS/h at 30°C and dropped over the optimum temperature. Moreover, the SAA values of the Low-R1 and Low-R2 were higher at 10–25°C and 10–35°C, respectively, than that of an anammox reactor inoculated with activated sludge in Kumamoto operated at 35°C (Mod-R). The apparent activation energy for anammox of Low-R1, Low-R2, and Mod-R were 108 kJ/mol (10–25°C), 73 kJ/mol (10–30°C), and 89 kJ/mol (10–35°C), respectively. Candidatus Kuenenia stuttgartiensis dominated in the Mod-R sludge. The Low-R1 sludge was comprised of Ca. K. stuttgartiensis, Ca. Brocadia caroliniensis and Ca. B. fulgida and uncultured anammox-like or planctomycete-like bacteria. The Low-R2 sludge was comprised of various uncultured anammox-like or planctomycete-like bacteria. As Low-R2 was constructed, enrichment of freshwater anammox bacteria at low temperature with seed sludge collected from cold regions is expected to be an effective strategy for anammox applications under a wide temperature range.