Four laboratory-scale autotrophic nitrogen removal bioreactors were implemented to investigate performance differences and microbial mechanisms under different temperatures (30, 25, 20, and 15℃). The results showed that the reactor performance under 30℃ was higher than others. When the temperature decreased from 30℃ to 25℃, total nitrogen removal efficiency reduced from 73% to 66%, and total nitrogen removal rate from 2.29 kg·(m3·d)-1 to 1.72 kg·(m3·d)-1. The morphology and particle size of the sludge did not change significantly (SMD:from 80.85 μm to 79.95 μm). When the temperature was 20℃, the total nitrogen removal efficiency reduced to 42%, the total nitrogen removal rate reduced to 1.18 kg·(m3·d)-1, and the sludge disintegration phenomenon occurred with particle size reduction (SMD:63.21 μm). When the temperature was 15℃, the total nitrogen removal efficiency reduced to 37%, and the total nitrogen removal rate got as low as 1.00 kg·(m3·d)-1. In addition to that, the reactor operation was difficult. The analysis of microbial community structure showed that the influence of temperature on anaerobic ammonia oxidizing bacteria is greater than that on ammonia oxidizing bacteria. This sensitivity to temperature of the anaerobic ammonia oxidizing bacteria was the main reason for the decreased performance under low temperature conditions.
Keywords: anaerobic ammonia oxidizing (ANAMMOX); autotrophic nitrogen removal; microbial community structure; swine wastewater; temperature.