Effects of hexavalent chromium on performance, extracellular polymeric substances and microbial community structure of anaerobic activated sludge in a sequencing batch reactor

BACKGROUND Bioremediation of Cr( VI ) to Cr( III ) was considered a promising and cost‐effective alternative to chemical and physical methods. However, Cr( VI ) had toxic effects on microorganisms. This study focused on exploring the effects of different Cr( VI ) concentrations on the performance of an anaerobic activated sludge reactor, extracellular polymeric substances ( EPS ) and microbial community structure. RESULTS Anaerobic sludge reduced and immobilized 100.0 mg L −1 Cr( VI ) in 24 h. When the Cr( VI ) concentration was increased from 0.0 to 50.0 mg L −1 , the production of EPS was enhanced from 231.4 to 1262.9 mg g −1 VSS . With 80.0 mg L −1 Cr( VI ) and 120.0 mg L −1 Cr( VI ), EPS production was inhibited. Increase of Cr( VI ) concentration changed the EPS components and had distinct effects on the functional groups of EPS . In addition, the increase of Cr( VI ) stress reduced the abundance of most bacteria. CONCLUSION Low Cr( VI ) concentrations had no effect on COD Cr and NO 3 ‐N removal, while 120.0 mg L −1 Cr( VI ) seriously inhibited on COD Cr , NO 3 ‐N and Cr( VI ) removal. This was due to the toxicity and electron competition ability of Cr( VI ). High Cr( VI ) concentrations (80.0 and 120.0 mg L −1 ) also inhibited EPS production. Cr( VI ) reduction was closely related with EPS . © 2017 Society of Chemical Industry