Environmentally friendly approach for advanced treatment of municipal secondary effluent by integration of micro-nano bubbles and photocatalysis

Abstract Numerous organic contaminants existing in the municipal secondary effluent (SE) have gained considerable attention because of their persistent nature and adverse environmental effects. In this study, micro-nano bubbles (MNB) and UV/Titanium dioxide (TiO2) system, both individual and in combination, were investigated for advanced treatment of the SE. The integrated MNB and photocatalysis system significantly improved the removal of chemical oxygen demand (COD) and persistent organic pollutants by 27.52 and 14.38%, respectively. The hybrid system efficiently decreased all five categories of organic contaminants according to excitation-emission matrix (EEM) spectrum, while the molecular weight (MW) fractions were decreased and the UV-absorbance at wavelength 254 nm (UV254) of MW (