Sulfate reduction by a haloalkaliphilic bench-scale sulfate-reducing bioreactor and its bacterial communities at different depths

Abstract

Efficient removal of high concentration sulfate from wastewater with high sodium concentration and pH is a challenge to date. In this study, a bench-scale haloalkaliphilic bioreactor was continuously operated for high-efficiency treatment of high concentration sulfate in simulation wastewater. It was found that up to 70% of sulfate was removed within hydranlic retention time of 24 h when sulfate concentration in influent was as high as 3000 mgl−1 at 1.0 M Na+ and pH 9.5. Sulfate removal rate reached 2.12 gl−1d−1, which was much higher than results in literatures. The bottom region of bioreactor contributed approximate sulfate removal of 40% to total sulfate reduction. Then, the rate decreased gradually with the reduction of depth. Moreover, the composition of organic acids was closely related to depth of the bioreactor. According to microbial community analysis, Desulfonatronovibrio might play the most important role in sulfate removal, and its relative abundance was the highest at bottom region. The abundance decreased gradually as reduction of the depth of bioreactor. In addition, these results revealed a dynamic process of sulfate removal and variety of bacterial communities in whole bioreactor. The identification of many microorganisms by 16S rRNA sequencing deepened the insight of SRB interaction with non-SRB in sulfate-removal process. The high-efficiency process offered a great biotechnological penitential for sulfate removal of industrial wastewater.