Role of sulfide on DNRA distribution and the microbial community structure in a sulfide-driven nitrate reduction process

Abstract

Abstract The two competing paths in microbial nitrate-reduction process are denitrification and dissimilatory nitrate reduction to ammonium (DNRA). In this study, a series of batch tests with five sulfide/nitrate (S/N) ratio were performed in a labratory-scale sequencing biofilm batch reactor (SBBR). This was done to investigate DNRA distribution in a sole sulfur-driven nitrogen conversion process. While DNRA increased its share in the sulfide-oxidizing autotrophic denitrification (SOAD) -dominant process as the S/N ratio was increased to 1.5:1, 1.7:1, and 2:1, the highest share was 35.3% at an S/N ratio of 1.5:1. The redox potential (ORP) pattern demonstrated that the knee points of NO3−-N and NO2−-N were separated when there was only SOAD, whereas the two points overlapped when DNRA coexisted with SOAD. 16S rRNA analysis revealed that the DNRA functional genera in autotrophic nitrate reduction process were Ignavibacterium, Hydrogenophaga, and Geobacter. DNRA divergence investigation could provide guidance for the strengthen biological nitrogen removal process especially coupled with anammox process.