A coupled ozonation-electrooxidation treatment for removal of bisphenol A, nonylphenol and triclosan from wastewater sludge

Organic emerging micropollutants are persistent during the biological process used in treatment plants and have the tendency to accumulate in the sludge. Since a common method of final sludge disposal is the land application, there are potential risks associated with the presence of contaminants within the sludge. In this work, the removal efficiency of endocrine-disrupting chemicals, namely bisphenol A, nonylphenol and triclosan from sludge was investigated using ozonation and electrooxidation using boron-doped diamond electrodes. Both procedures were studied to determine the optimal conditions (pH, current density and ozone flow) for removing these chemicals in an hour. With the obtained conditions, a coupled system ozonation-electrooxidation was used with the goal to have better pollutant elimination. Results indicate that these compounds could be effectively removed by the coupled system; the diminutions were Bisphenol A 86%, nonylphenol 68% and triclosan 67%. Also improvements in the quality of aqueous phase were obtained, and for instance, the chemical oxygen demand, color and turbidity, were abated in 62, 61 and 66%, respectively. Moreover, an additional advantage of the coupled system is the absence of any secondary pollution.