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The increasing use of impaired water supplies to provide high quality drinking and reclaimed water isfueling the application of membrane processes. A major constraint to their cost-effective operation ismembrane fouling, particularly fouling by natural organic matter (NOM). NOM fouling ofmembranes is poorly understood and research is needed to develop more effective methods for itscontrol, particularly with the rapid increase in and increasing size of low pressure (MF/UF)membrane systems. To provide a better and more fundamental understanding of NOM fouling ofmembranes, a comprehensive study, funded by AwwaRF, was conducted that focused oncharacterization of fouling of MF and UF membranes by three classes or categories of NOM foulants:allochthonous, represented by humic and fulvic acids; autochthonous or algal-derived; and, effluentorganic matter. Study objectives included: identifying problematical NOMfoulants; quantifying the NOM fouling potential of a variety of waters; distinguishing between NOMfractions that contribute to reversible and irreversible fouling; and, assessing the properties of membranesthat influence fouling and developing a predictive tool or surrogate test that could be used to measurethe "NOM fouling index" of a given water. The research was conducted by using a combination ofbench, pilot and full-scale tests conducted with a variety of flat-sheet and hollow-fiber MF/UFmembranes. Stirred cell and small-scale hollow fiber bench test apparatuses were evaluated forfouling prediction and results compared with pilot to assess viability. A variety of analytical methods,included LC/DOC, XAD resin, AFM, GC/MS pyrolysis and AFM were employed for foulantcharacterization in aqueous and solid phases. Bench results show clear differences in fouling potentialby different waters/NOM types, for different membrane materials on a given water and between waterand chemical backwashes. Good correlations were observed between different bench test methods.Characterization of NOM from raw, filtrate and backwash samples show that polysaccharides andlarge MW fraction of NOM is primary fouling constituent, relatively independent of source or NOMtype. The results of this research will provide the drinking water/reuse communities with betterunderstanding of NOM fouling, effectiveness of membrane materials/properties andbackwashing/chemical washing in managing NOM fouling and value of rapid, bench scale tests inrapid NOM fouling prediction. This information can be utilized for more cost effective design andoperation of full-scale MF/UF facilities. Includes reference, tables, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 20File Size: 1 file , 1.2 MB