Performance of anammox UASB reactor treating low strength wastewater under moderate and low temperatures

An integrated approach to enhance and maintain high anammox activity and abundance in an upflow anaerobic sludge blanket (UASB) treating low strength wastewater under moderate and low temperatures was developed. A quantitative PCR assay showed the abandance of anammox bacteria to be 1.68±0.08×10(9) copies/ml in mixed liquor when the temperature was 30 °C and was maintained at the level of 1.93±0.41×10(9) copies/ml in mixed liquor at 16 °C. A nitrogen removal rate (NRR) of up to 5.72 kg N/m3/d was achieved with a hydraulic retention time (HRT) of 0.12 h at 30 °C, while nitrite and ammonium removal efficiencies were 94.35% and 92.81%, respectively. NRR decreased with a decrease in temperature and was maintained at 2.28 kg N/m3/d with an HRT of 0.28 h when at 16 °C, while nitrite and ammonium removal efficiencies were 92.31% and 78.45%, respectively. The emission rate of the greenhouse gas N2O was below 0.006% of the NRR in the anammox UASB reactor treating low strength wastewater.