Removal of persistent chemical oxygen demand from pharmaceutical wastewater by ozonation at different pH

Ozonation has been applied to treat the actual pharmaceutical wastewater samples for the removal of chemical oxygen demand. Ozonation can generally achieve higher pharmaceuticals removal rates as compared to conventional processes as ozone reacts with a variety of complex compounds, intermediates and breaks them into simpler ones. Chemical oxygen demand removal study can be useful to elucidate the effect of pH on ozonation. In this study, an attempt has been made to assess the impact of ozonation on the removal of persistent chemical oxygen demand from actual pharmaceutical wastewater samples under varying conditions of pH from 4 to 10. Lower chemical oxygen demand removal efficiency was observed under an acidic medium (pH 4.0) as compared to those at pH 6.9 and 10.0. Treatment at alkaline pH 10.0 using 30.0 mg L-1 ozone for a treatment time of 10 min resulted in 66.67% chemical oxygen demand removal from the sample. It was reported that ozonation at higher pH favored chemical oxygen demand removal from the sample. At elevated pH, indirect reactions are the main means of ozonation, and also as the rate of formation of hydroxyl radicals substantially increases, it can be said that the percentage of chemical oxygen demand removal was significant in the alkaline medium. Improved biodegradability (ratio of biochemical oxygen demand to chemical oxygen demand = 0.455) after 10 min of treatment showed the effect of ozonation on the actual sample. It was concluded that ozone treatment alone can remove pharmaceuticals from the actual wastewater sample.