Microbial community structure and function in response to the shift of sulfide/nitrate loading ratio during the denitrifying sulfide removal process

Cong Huang, Zhi-ling Li, Fan Chen, Qian Liu, You-kang Zhao, Ji-zhong Zhou, Ai-jie Wang

State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, PR China.

Abstract

Influence of acetate-C/NO₃^--N/S^2- ratio to the functional microbial community during the denitrifying sulfide removal process is poorly understood. Here, phylogenetic and functional bacterial community for elemental sulfur (S⁰) recovery and nitrate (NO₃−) removal were investigated with the switched S²−/NO₃− molar ratio ranged from 5/2 to 5/9. Optimized S²−/NO₃− ratio was evaluated as 5/6, with the bacterial genera predominated with Thauera, Enterobacter, Thiobacillus and Stappia, and the sqr gene highly expressed. However, insufficient or high loading of acetate and NO₃− resulted in the low S0 recovery, and also significantly modified the bacterial community and genetic activity. With S²−/NO₃− ratio of 5/2, autotrophic S²− oxidization genera were dominated and NO₃− reduction activity was low, confirmed by the low expressed nirK gene. In contrast, S²−/NO₃− ratio switched to 5/8 and 5/9 introduced diverse heterotrophic nitrate reduction and S⁰ over oxidization genera in accompanied with the highly expressed nirK and sox genes.

Graphical abstract

Keywords: Denitrifying sulfide removal process; Continuous stirred tank reactor (CSTR); Sulfide/nitrate loading ratio; Microbial community structure; Function.