Rapid granulation using calcium sulfate and polymers for refractory wastewater treatment in up-flow anaerobic sludge blanket reactor.

Long start-up period and slow granulation are major restraints in up-flow anaerobic sludge blanket (UASB) reactors for the treatment of refractory wastewater. In this study, Calcium sulfate (CaSO), CaSO/guar gum (GG), and CaSO/cationic polyacrylamide (CPAM) were used to enhance granulation during the treatment of phenolic wastewaters in UASB reactors. Use of CaSO, CaSO/GG, and CaSO/CPAM increased formation of granules (>0.25 mm) by 7%, 21% and 40%, respectively, after 90 days in comparison with the control. Use of CaSO/GG and CaSO/CPAM at an organic loading rate of 2.89 kg chemical oxygen demand (COD) m d increased the COD removal efficiency by 9% and 3%, respectively, in comparison with the control (75%). The CaSO enhanced the granulation rate as nuclei and the subsequent dissolution of CaSO improves the activity of methanogens. Polymers facilitated bacteria adhesion and improved the diversity of phenols-degrading bacteria. This study describes a new method for rapid granulation in UASB reactors when treating toxic and refractory wastewaters.