Coupling of acoustic/hydrodynamic cavitation with ozone (O3), hydrogen peroxide (H2O2), magnesium oxide (MgO) and manganese dioxide (MnO2) for the effective treatment of CETP effluent

Abstract

In the current work, chemical oxygen demand (COD) reduction of Common Effluent Treatment Plant (CETP) effluent was investigated using acoustic (AC) or hydrodynamic cavitation (HC) coupled with ozone, O3/H2O2, O3/MnO2 and O3/MgO. AC was based on a dual-stepped ultrasonic horn whereas HC was based on an orifice applied as cavitating device. Maximum COD reduction of 88.66% was obtained for the approach of AC/O3/MgO followed by 85.13%, 67.12%, 56.28% and 52.23% for AC/O3/MnO2, AC/O3/H2O2, AC/O3 and only ozone respectively within 60 min at natural pH of 9. For HC, maximum COD reduction of 88.36% was achieved for HC/O3/MgO followed by 83.11%, 64.77%, 54.61% and 51.12% for HC/O3/MnO2, HC/O3/H2O2, HC/O3 and ozone operated in recirculation mode without HC respectively. The influence of ̇OH radical scavengers as Cl¯, CO32¯ and HCO3¯, and ozone scavenger as S2O32¯ on the efficacy of different approaches has also been demonstrated to establish the controlling mechanisms. The experimental data was fitted to the Generalized Kinetic Model (GKM) considering the formation of intermediates along with the determination of volumetric mass transfer coefficients on the basis of dissolved ozone concentration. The cost estimation for various approaches have also been performed. Overall it has been clearly demonstrated that HC based catalytic ozonation offers promise for treatment of effluents in the CETP.