Effect of salinity on the operational efficiency, microbial community, and metabolism of a bioelectrochemical-granular sludge coupled system for treating sulfate wastewater

The effect of salinity on biological processes makes the removal of sulfate from saline wastewater challenging. The objectives of this study were to investigate the effect of salinity on the removal of sulfur-containing wastewater from a coupled anaerobic baffled reactor and microbial electrolysis cell (ABR-MEC). Results showed that at a NaCl concentration of 20 g/L, the anaerobic and aerobic systems were 78 % and 62 %, respectively, effective in removing SO42−. The polysaccharides and proteins of loosely bound-extracellular polymeric substances (LB-EPS) and tightly bound-extracellular polymeric substances (TB-EPS) decreased as the NaCl concentration increased. The dominant genera changed to Solidesulfovibrio, Desulfovibrio, and Klebsiella, with relative abundances of 10.40 %, 4.18 %, and 3.88 %, respectively. During sulfur metabolism, the abundance of AprAB functional genes was 0.021 %, 0.024 %, and 0.047 % at NaCl concentrations of 0 g/L, 10 g/L, and 20 g/L, respectively, with the relative abundance showing an increasing trend, and the pathway of anisotropic sulfur metabolism was strengthened.