Application of advanced oxidation processes to remove refractory compounds from dye wastewater

The purpose of this study was to investigate the efficacy of ozonation and three AOPs (O-3/H2O2, O-3/UV, and O-3/H2O2/UV) on synthetic dye-containing wastewater with regard to the removal of chemical oxygen demand ( COD) and color and biodegradability (BOD5/COD). At hydrogen peroxide levels above the optimal value, H2O2 tended to accumulate in the reactor, leading to a decrease in COD removal efficiency, because it acted as a radical scavenger. Higher recirculation flow rates increased COD and color removal in the combined UV process. Compared with the O-3/H2O2 process, the O-3/UV process enhanced COD removal mildly. Biodegradability increased approximately 12-fold after 150 min of retention time. Although all processes removed color within a short operational time, the O-3/H2O2/UV process had the highest removal efficiency of COD and enhancement of biodegradability of the processes that we tested.