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

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 (S-0) recovery and nitrate (NO3) removal were investigated with the switched S-2 /NO3 molar ratio ranged from 5/2 to 5/9. Optimized S-2 /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 S-0 recovery, and also significantly modified the bacterial community and genetic activity. With S-2 /NO3 ratio of 5/2, autotrophic S-2 oxidization genera were dominated and NO3 reduction activity was low, confirmed by the low expressed nirK gene. In contrast, S-2 /NO3 ratio switched to 5/8 and 5/9 introduced diverse heterotrophic nitrate reduction and S-0 over oxidization genera in accompanied with the highly expressed nirK and sox genes. (C) 2015 Published by Elsevier Ltd.