Significant improvement in biodegradability of a real Optical Brightening Agent (OBA) wastewater using small doses of Fenton's reagent.

Optical Brightening Agent (OBA) wastewater (OBAW) has been reported to be highly resistant to biodegradation. In this study, a real OBAW from an industry which was already treated using primary and secondary treatments (residual COD of secondary clarifier overflow (SCO): 3400-3700 mgL-1) was further treated by Fenton's treatment (FT). Zahn-Wellens biodegradability test revealed that using small doses of H2O2 and Fe+2, the biodegradability of SCO improved to 90% as compared to ∼18% without FT. UV-Vis analysis revealed that ca. 80% of initially present OBAs were removed by treatment sequence outlined in this study. Biodegradability study on individual raw wastewaters from four types of OBAs (designated OBA-TS, OBA-DS-U, OBA-HS, and OBA-DS-D) being manufactured at the time of this study, revealed that OBA-TS wastewater was the most biodegradable (>95% biodegradability) followed by OBA-DS-U (∼60%), OBA-HS (∼20%), and OBA-DS-D (<5%). Application of FT improved the biodegradability of these streams as: OBA-DS-U (∼70%), OBA-HS (∼60%), and OBA-DS-D (∼50%). A treatment sequence consisting of waste coal dust (WCD) pretreatment-FT-biodegradation is a novel, economical, and sustainable approach to treating highly recalcitrant OBA wastewater.