Fouling Elimination of PTFE Membrane under Precoagulation Process Combined with Ultrasound Irradiation

Abstract

Precoagulation is one of the effective pretreatments in membrane filtration. This process mitigates membrane fouling, which is the major drawback of membrane technology in drinking water and wastewater treatment. This study investigated the effects of precoagulation under different coagulation mechanisms on membrane fouling. Use of ultrasound in polytetrafluoroethylene (PTFE) membrane cleaning was also evaluated. In precoagulation, synthetic raw water was precoagulated using aluminum sulfate at different coagulation mechanisms, named electrostatic patch effect (EPE), charge neutralization (CN), and sweep flocculation (SW). Flocs produced from different coagulation mechanisms exhibited different sizes, structures, and strengths. Likewise, the fouling type generated from each mechanism was demonstrated as pore blocking for EPE, cake formation for SW, and combination phenomenon for CN. Moreover, this study indicated that the membrane flux was enhanced in the sequence of EPE > CN > SW. The flux recovery rate after ultrasonic cleaning was in the sequence of SW > CN > EPE. Finally, this study evidenced that the floc characteristics from various coagulation mechanisms affected membrane performance, fouling types, and ultrasonic cleaning efficiency. DOI: 10.1061/(ASCE)EE.1943-7870.0000406. (C) 2012 American Society of Civil Engineers.