Effect of pre-treatment on dye degradation in aerobic reactor

Abstract

Application of ozone and Fenton’s reagent was investigated as a pre-treatment to improve the biodegradability of acid blue 113 (AB 113) dye used in the tanneries and subsequent treatment in aerobic reactor. Pre-ozonation of 5 min improved the BOD5/COD ratio of AB 113 dye from 0.029 to 0.296 due to the partial oxidation of the dye molecules and resulted in the reduction in COD of 22%, with the generation of biodegradable organics. Fenton’s oxidation as pre-treatment at the optimum dose of H2O2/COD ratio of 1.0 (w/w) and H2O2/Fe2+ ratio at 9.7 (w/w) resulted in 45% reduction of COD due to mineralization, with subsequent improvement in BOD5/COD ratio from 0.029 to 0.411. Combined process of ozonation and aerobic treatment resulted in 55% removal of COD and the treated effluent had a BOD5 and COD of 45 and 355 mg/L, respectively. Combined Fenton and aerobic treatment resulted in 82% removal of COD and 25 and 230 mg/L of BOD5 and COD was observed in the treated effluent. FT-IR results also supported the finding that the application of ozonation and Fenton’s oxidation effectively decolorizes the dye with partial mineralization and resulted in generation of biodegradable organics like acids, aldehydes, and ketones. High removal of the biodegradable organics in the aerobic reactor was observed for Fenton pre-treated AB 113 dye.