Removal of emerging contaminant and fouling control in membrane bioreactors by combined ozonation and sonolysis

The combination of chemical and biological treatment is a promising solution to remove emerging contaminants, e.g., pharmaceuticals, from wastewater for its future reuse. In this study, the combination of ozonation and ultrasound (O3/US) was examined as a pretreatment prior to membrane bioreactor (MBR). The effects of O3/US on the removal of selected pharmaceuticals, including diclofenac (DCF), sulfamethoxazole (SMX) and carbamazepine (CBZ), and MBR fouling control were investigated. The variation of the toxicity potential of the MBR influent was also assessed. The O3/US treatment was effective in reducing fouling, mainly due to its effects on the microbial metabolism products in the MBR. Extracellular polymeric substance (EPS) concentration was reduced by 50%. Improved operating conditions resulted in higher removal rates for pharmaceuticals in the MBR effluent, with removal efficiency in the range of 80e84%. However, the O3/US treatment alone was not efficient in removing the toxicity of wastewater. This was likely due to the formation of intermediate products that are more toxic than the parent compounds. These intermediate products were observed to be biologically oxidized by MBR, with a 80% reduction of the toxicity potential in the MBR permeate compared to the influent.