Membranes used in filtration processes commonly experience substantial flux declines when exposed to feed water contaminants such as, for example, particulates or suspensions of organic, inorganic or biological materials. The contaminants can cause membrane fouling, which increases the operating pressure required for a constant rate of water production, decreases the service lifetime of the membrane, and increases operating costs. To reduce fouling, the feed water entering the membrane may be pre-treated, or the membrane may be periodically chemically cleaned to remove contaminant deposits. Although pretreatment processes can remove certain foulants such as large particles or biomolecules, dissolved organic matter can remain on the membrane following the pretreatment step.
To improve fouling resistance, a fouling-resistant polymer may be grafted onto the membrane surface. This grafting process has proven in some cases to be difficult, particularly when a membrane is to be utilized in an application where both fouling resistance and antimicrobial properties are desired. Some membrane-modifying polymers are not water soluble and/or can be difficult to synthesize, while others do not form a crosslinked network, which results in a surface grafting density that is very low.