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Nanofiltration of surface water was investigated in pilot-scale, comparing biofiltration andrapid media filtration as simple pre-treatment options. The nanofilters were operatedaccording to the approach established in parts of Scandinavia, where pretreatment is limitedand the membrane flux is low.Biofiltration resulted in feed water containing lower concentrations of bacteria, total organic carbon (TOC) and Biodegradable organic carbon(BDOC) and resulted in a profoundly decreased biofilm formation on glass slides compared torapid media filtration. Transmembrane pressure increase was in average 5 fold lower for thenanofilter with biofiltration as pretreatment (NF-BAC) compared to the nanofilter with rapidmedia filtration as pretreatment (NF-DM). The NF-BAC membranes contained lessbiological-, organic- and inorganic fouling than the NF-DM membranes. Iron, aluminium andsilica were the dominant inorganic elements, while biopolymers (polysaccharides, proteinsand aminosugars) were the dominant organic fouling fraction, despite low concentrations inthe feed waters. Although NF-Bio contained less fouling matter than NF-RMF, no differencein the fouling composition was observed that would point out a specific componentresponsible for the reduced transmembrane pressure. The results of this study indicate thatbiofiltration, as a simple pretreatment option, can significantly mitigate fouling problems inlow flux NF installations for natural organic matter (NOM) removal from surface water. Includes 21 references, table, figures.

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Edition: Vol. - No. Published: 03/01/2007 Number of Pages: 7