Removal performance and membrane fouling mitigation mechanism of electrocoagulation membrane dissolved ozone flotation

To enhance the removal of wastewater treatment plant effluent organic matter, the electrocoagulation membrane dissolved ozone flotation (EMDOF) method for simultaneous filtration and in-situ cleaning (SFC) was established. EMDOF exhibited better dissolved organic matters (DOM) removal efficiency than the electrocoagulationmembrane (ECM) and ozonation-membrane (OM) processes. Under optimal operating conditions, i.e. current density 10 mA/cm2 and ozone aeration rate of 200 mL/min, EMDOF achieved dissolved organic carbon (DOC), UV254, and color removal efficiencies of 35.22%, 71.48%, 69.44%, respectively, within 990 min. The turbidity of the EMDOF effluent stabilized at 0 NTU. The normalized flux (J/J0) of EMDOF was lower than that of OM under the same ozone dosage, but higher than that of ECM under the same current density. SFC removed the sludge from the membrane surface and better eliminated the reversible membrane fouling. The J/J0 restored by SFC reached 90% of the preliminary stage and stabilized at 63% in the later stages. Scanning electron microscopy and particle size distributions showed that larger flocs and more porous cake layers formed with EMDOF than with ECM, resulting in superior membrane fouling mitigation.