Treatment of laundry wastewater containing residual surfactants using combined approaches based on ozone, catalyst and cavitation

The present work investigates the treatment of wastewater by degrading detergents and residual surfactants using individual and combined approaches based on ozone, catalyst and cavitation. The intensification of ozonation has been investigated by the addition of solid ZnO and CuO catalysts. The extent of degradation increased with catalytic ozonation as compared to non-catalytic ozonation. In comparison, the combination with cavitation did not yield any beneficial results. The study of the effect of initial pH of the solution and effect of different catalyst loadings in catalytic ozonation with ZnO established that the maximum degradation as 89.3% was obtained at initial pH of 9 and 0.1 g L-1 of catalyst loading. It was also demonstrated that the reaction followed first order kinetics with rate constant as 0.067 min(-1). BOD analysis at optimized conditions demonstrated that catalytic ozonation efficiently converts non-biodegradable harmful surfactants in wastewater to easily digestible compounds, which means that this can be a complimentary process to biological oxidation. Overall the work has clearly demonstrated the efficacy of catalytic ozonation approach for treating the laundry wastewater.