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AWWA WQTC60679
- Organic Fouling of Polyamide Reverse Osmosis: Effect of Natural Organic Matter Properties on Membrane Performance
- Conference Proceeding by American Water Works Association, 11/15/2004
- Publisher: AWWA
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This study examined the effects of conventional pretreatment and conventional pretreatment withozone and biofiltration (O<sub>3</sub>/BF) on organic fouling of reverse osmosis (RO) membranes. Projectgoals included assessing the effects of O<sub>3</sub>/BF on natural organic matter (NOM) and how changesto NOM affect RO fouling. NOM was characterized using ultrafiltration (UF) size fractionationwith ultraviolet absorbance at 254 nm (UV<sub>254</sub>) to produce the following size fractions: >10 kDa,10-3 kDa, 3-1 kDa, and <1 kDa. Salt rejection, specific flux, and differential pressure data wereused to evaluate RO membrane performance. Fouled RO membranes were analyzed withscanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fouriertransform infrared photoacoustic spectroscopy (FTIR-PAS). Results showed conventionalpretreatment produced lower average turbidity and silt density index (SDI) than O<sub>3</sub>/BF, althoughaverage SDI values for both pretreatment processes were higher (>3.0) than recommended forRO membranes. NOM size distribution varied substantially between samples from the samelocation, preventing an assessment of the effect of O<sub>3</sub>/BF on NOM and RO fouling. SEMrevealed visual morphologies indicative of colloidal and organic fouling. EDS identifiedaluminum silicates and silica as sources of colloidal fouling, particularly after O<sub>3</sub>/BF. FTIR-PASindicated O<sub>3</sub>/BF caused more fouling and identified proteins, polysaccharides, and aluminumsilicates as the primary foulants, although overlapping polysaccharide and aluminum silicatespectra obscured the relative contributions of these materials. Overall, conventional pretreatmentyielded better RO performance and less fouling than O<sub>3</sub>/BF pretreatment. Enhancing NOMcharacterization techniques, evaluating alternative NOM characteristics, or reducing interferencefrom colloidal fouling could improve future studies on organic fouling of RO membranes. Includes 11 references, tables, figures.
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