Integrated simultaneous desulfurization and denitrification (ISDD) process at various COD/sulfate ratios

The integrated simultaneous desulfurization and denitrification (ISDD) is a novel treatment process to handle sulfate and nitrate-laden wastewaters of high loadings. This study experimentally explored the effect of COD/SO42- ratio on the performance of ISDD process, particularly considering the complex interactions between sulfate-reducing bacteria (SRB), heterotrophic denitrifiers (hNRB) and autotrophic denitrifiers (aNRB). There existed an optimal COD/SO42- ratio (=1.5:1 in the present study) to reach 100% SO42- and NO3- removals and 42.6% S⁰ recovery. At COD/SO42-=1.5:1, the functional strains could form granules with high retention in the ISDD reactor. The microbial community analysis identified the SRB, hNRB and aNRB in the studied system, whose shifts correlated well with the noted ISDD performance change at different COD/SO42- ratio. Interactions between different groups of bacteria and the possible strategy to enhance the ISDD performance were discussed.