A review of the impact of chemical pretreatment on low-pressure water treatment membranes

Abstract

Historically, microfiltration (MF) and ultrafiltration (UF) membranes have been used to remove turbidity, particulate matter, and pathogens. Chemical and physical pretreatment, however, can greatly expand the use of MF and UF membrane systems beyond turbidity and microorganism removal. Both MF and UF membrane systems may be used to remove a variety of chemical contaminants such as arsenic, pesticides, taste and odour, iron, and manganese, provided that the proper water chemistry is attained to convert the contaminants to a particulate form. In addition to enhancing the removal of dissolved contaminants, chemical pretreatment processes such as coagulation have been shown to improve membrane performance by reducing the rate of membrane fouling. Several issues, however, still remain to be resolved before chemical pretreatment can be applied optimally in the water treatment membrane field. These issues include the impact of chemical pretreatment on the performance of membrane systems (i.e., membrane reversible fouling, chemical cleaning frequency), the compatibility of these chemicals with membrane materials, the optimum conditions for chemical pretreatment, and overall cost and benefits of chemical pretreatment to MF and UF membrane systems. Key words: microfiltration, ultrafiltration, chemical pretreatment, membrane fouling, natural organic matter, coagulation, clarification, oxidation, contaminant removal, process optimization.