Nanofiltration Fouling Control for Surface Waters with High Dissolved Organic Carbon and Hardness

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Potable water from high DOC sources often exceeds water quality standards for trihalomethanes (THMs), which are potentially carcinogenic chlorine disinfection by-products. Dual membrane plants, that combine Ultrafiltration (UF) and Nanofiltration (NF), can remove DOC and reduce THM concentrations, but their NF membranes are prone to frequent and pronounced fouling, reducing their life and performance efficiency, and increasing operation costs. Membrane fouling can be defined as the loss of filtration performance due to undesirable formation of deposits (foulants) on the membrane surface. Fouling due to organic matter and or biofilms is one of the main problems of high pressure membranes like NF. Furthermore, membrane fouling is exacerbated by the existence of high concentrations of calcium and magnesium cations (water hardness). A high concentration of organic carbon promotes the development of microbial communities on membrane filters. Microbes can foul membranes by adhering directly to membrane surfaces, or indirectly by attaching to adsorbed DOC. Advanced Oxidation Processes (AOP) have been reported to mitigate NF membrane fouling. This could be due to inactivating microorganisms and/or changing the properties of organic compounds so they do not adhere to the NF membrane material. The overall objectives of this proposed project are (1) to establish the role of organic compounds and microbial communities in the formation of the foulant on the NF membrane and (2) explore advanced oxidation before NF to mitigate membrane fouling. All samples will be collected from the Brandon pilot plant and a bench-scale membrane apparatus. AOP may be cheaper than methods involving removal of organic compounds that are typically practiced, making the membrane filtration more effective and affordable. Two M.Sc. and several undergraduate students will be trained as Canadian experts on the challenges inherent to membrane filtration-based water treatment, especially for waters typical of the Canadian Prairies that are most difficult for this type of treatment. This research will have a large economic impact for the partners, because the NF fouling problem represents the main operating cost of water treatment process.