Applying permanganate/bisulfite (PM/BS) pre-oxidation enhanced coagulation to control fouling of ultrafiltration membrane in drinking waterworks

Coagulation is an effective pre-treatment step for ultrafiltration (UF) drinking water treatment but is limited by the inability to regulate membrane fouling , particularly organic and biological fouling. Herein, we propose a permanganate/bisulfite (PM/BS) pre-oxidation enhanced coagulation process (PM/BS + coagulation) as UF pre-treatment and apply it to treat samples of natural surface waters. The results indicate that PM/BS + coagulation demonstrated superior performance in mitigating membrane fouling. For the four different types of real water, the specific membrane flux decline of UF following PM/BS + coagulation was 4.2 %–22 % less than that of UF following coagulation, and PM/BS + coagulation decreased the total filtration resistance by 21.7 %–74.9 % compared to coagulation alone. To achieve the best membrane fouling alleviation, PM/BS was suggested for use with aluminum polychloride-coagulation under optimized oxidation C ox T ox , coagulant dosage, GT value, and sedimentation time. PM/BS + coagulation pre-treatment controlled UF membrane fouling by: 1) directly changing the UF feed water quality (e.g., composition and properties of organic matter, amount and properties of particulate matter , quantity, and metabolic activity of microorganisms) and affecting the foulant characteristics; and (2) indirectly adjusting the foulants' depositional environment (e.g., zeta potential , roughness, hydrophobicity , and interfacial free energy). These two factors influenced the subsequent fouling development. This work highlights the potential of PM/BS + coagulation to assist UF in producing high-quality drinking water while preserving a low membrane fouling propensity.