Abstract
The optimal temperature for anaerobic ammonium oxidation (anammox) is generally 30－37℃. This temperature range, which is higher than usual wastewater temperature, implies that the anammox reactor requires heat energy for efficient nitrogen removal. Therefore, the anammox process which is applicable at ambient temperature (20－25℃) is needed to develop more versatile and sustainable nitrogen removal technologies. This study was conducted to start-up lab-scale anammox reactors packed with a nonwoven fabric material at 20℃ using various inoculum sources. Reactor 1 was inoculated with activated sludge sampled in Kumamoto, a temperate region of Japan. Reactor 2 was inoculated with activated sludge obtained from Hokkaido, a subarctic region. Reactor 3 was inoculated with groundwater microorganisms sampled from Kumamoto. At 800 days from the start-up of the reactors, Reactors 1 and 2 achieved high nitrogen removal rates (NRR) of 0.64 kg－N/m3/day at 20℃ with the typical anammox reaction ratio. Although the nitrogen removal was unstable, the NRR increased to 0.38 kg－N/m3/day in Reactor 3 after 700 days. The nitrogen reaction ratio in Reactor 3 indicated the simultaneous occurrence of anammox and nitrification. Results suggest that anammox bacteria, which can grow at ambient temperature, are ubiquitous in the environment.
