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 CODCr and NO3‐N removal, while 120.0 mg L−1 Cr(VI) seriously inhibited on CODCr, NO3‐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