Effect of electron donor source on the treatment of Cr(VI)-containing textile wastewater using sulfate-reducing fluidized bed reactors (FBRs)

The treatment of Cr(VI) containing textile wastewater was studied in ethanol and glucose-fed sulfate-reducing fluidized bed reactors at 35 °C for around 250 days. The synthetic wastewater contained Cr(VI) (5–45 mg L−1), azo dye (Remazol Brilliant Violet 5R) (100–200 mg L−1), sulfate (2000 mg L−1) and ethanol or glucose (2000 mg L−1 chemical oxygen demand (COD)). The robustness of two FBRs was assessed under varying Cr(VI) and azo dye loadings. Both reactors performed well in terms of COD, sulfate, color and Cr(VI) removals. However, ethanol-fed FBR performed better than glucose-fed one. The COD, sulfate, chromium and color removals at the highest Cr(VI) concentration (45 mg L−1) in ethanol-fed FBR were around 75%, 95%, 93%, and 99%, respectively. Further increase in influent Cr(VI) concentration adversely effected reactor performance. The COD, sulfate, chromium and color removals at 45 mg L−1 Cr(VI) in glucose-fed FBR were around 60%, 50%, 93%, and 76%, respectively.