Studies on enhancing the biodegradation of tannins by ozonation and Fenton's oxidation process

Tannins are used in vegetable tanning and re-tanning processes. The biochemical oxygen demand (BOD5) to chemical oxygen demand (COD) ratio of 0.196 indicated that tannins are recalcitrant and persistent. Ozonation as pre-treatment resulted in 20% and 49% of COD and total phenol removal due to mineralization and the BOD5/COD ratio increased to 0.298. Fenton's reagent pre-treatment resulted in 51% and 85% reduction of COD and phenol removal due to mineralization, with subsequent improvement in BOD5/COD ratio from 0.196 to 0.443. Wastewater pre-treated with Fenton's reagent resulted in BOD5 and COD of 26 and 210 mg/L in the aerobic treated final effluent.