An anaerobic ammonium oxidation (anammox) process for ammonia-rich wastewater treatment has not been reported at temperatures below 15 °C. This study used a gel carrier with entrapped anammox bacteria to obtain a stable nitrogen removal performance at low temperatures. In a continuous feeding test, a high nitrogen conversion rate (6.2 kg N m-3 day-1) was confirmed at 32 °C. Nitrogen removal activity decreased gradually with decreasing operation temperature; however, it still occurred at 6 °C. Nitrogen conversion rates at 22 and 6.3 °C were 2.8 and 0.36 kg N m -3 day-1, respectively. Moreover, the stability of anammox activity below 20 °C was confirmed for more than 130 days. In batch experiments, anammox gel carriers were characterized with respect to temperature. The optimum temperature for anammox bacteria was found to be 37 °C. Furthermore, it was clear that the temperature dependence changed at about 28 °C. The apparent activation energy in the temperature range from 22 to 28 °C was calculated as 93 kJ mol-1, and that in the range from 28 to 37 °C was 33 kJ mol-1. This value agrees with the result of a continuous feeding test (94 kJ mol-1, between 6 and 22 °C). The nitrogen removal performance demonstrated at the low temperatures used in this study will open the door for the application of anammox processes to many types of industrial wastewater treatment.
ASJC Scopus subject areas
- Molecular Biology