Performance of a haloalkaliphilic bioreactor under different NO3-/SO42- ratios

•Haloalkaliphilic microorganisms were used to reduce sulfate and nitrate.•Sulfide concentration reached up to 703 mg/l.•There was no sulfide inhibition to haloalkaliphilic microorganisms.•Bacterial community of haloalkaliphilic bioreactor was studied.

Effects of NO3-/SO42- ratio on denitrification and sulfate removal efficiency were investigated in model experiments applying haloalkaliphilic bioreactor. The reduction of both substrates performed well at different NO3-/SO42- ratios ranging from 17.6 to l.5. The removal rates of nitrate and sulfate were 6 and 1.39 kg m−3 d−1, respectively, at NO3-/SO42- ratio 3.0, while sulfide concentration reached up to 703 g m−3. The major sulfate-reducing and denitrifying bacteria were Desulfonatronovibrio sp. and Halomonas campisalis  , respectively. Decrease in NO3-/SO42- ratio led to obvious changes in bacterial community. Although the sulfate reducers became dominant, the population of denitrifying ones also increased as it was demonstrated by analysis of PCR-amplified 16S rDNA fragments, which suggested that SRB and DB coexisted well in bioreactor.