The variation on nitrogen removal mechanisms and the succession of ammonia oxidizing archaea and ammonia oxidizing bacteria with temperature in biofilm reactors treating saline wastewater

Ziyuan Lin, Wei Huang, Jiong Zhou, Xuejie He, Jiale Wang, Xiantao Wang, Jian Zhou

Key Laboratory of the Three Gorges Reservoir Region’s Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China.

Abstract

To reveal nitrogen removal mechanisms under environmental stresses, biofilm reactors were operated at different temperatures (10°C–35°C) treating saline wastewater (salinity 3%). The results showed nitrogen removal efficiency was 98.46% at 30°C and 60.85% at 10°C, respectively. Both ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) participated in nitrification. 94.9% of the overall ammonia oxidation was attributed to AOA at 10°C, but only 48.2% of that was undertaken by AOA at 35°C. AOA had a greater contribution at low temperature, which demonstrated that nitrogen removal pathway varied with temperature. Aerobic denitrification was more stable than anoxic denitrification. High-throughput sequencing showed Crenarchaeota was the dominant AOA (97.02–34.47%), cooperating with various heterotrophic AOB. Real-time PCR indicated that AOA was three orders of magnitude more abundant than AOB. AOA was more resistant to low temperature and high-saline stresses. Ammonia oxidizers had distinct responses to temperature change and showed diverse relationships at different temperatures.

Keywords: Saline wastewater, Biological nitrogen removal, Temperature, Ammonia oxidizing archaea, Microbial community succession.