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Parallel experiments were conducted to determine the source of organic/biological fouling ofreverse osmosis (RO) membranes when operated only under pilot-scale conditions. Testing wasconducted using a 230 L/min conventional filtration (rapid mix/flocculation/sedimentation/filtration) package plant (CPP) and a 2,000 ML/day full-scale treatment plant (FTP) aspretreatment to separate RO membrane test units. Coagulation consisted of 10 mg/L of alum and2.0 mg/L of cationic polymer. A 2.5 to 3.0 mg/L free chlorine residual was maintained at thefilter effluent and converted to chloramines through ammonium sulfate addition (3:1 chlorine toammonia w/w ratio). Membrane performance was based on normalized flux and salt rejectiondata. Membrane surface analyses included scanning electron microscopy, energy-dispersivespectroscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy.Microbial activity and community analyses were conducted through: fluorescence stainingwith 4',6'-diamidino-2-phenylindole; polymerase-chain reaction amplification of isolatedbacterial DNA; and, microscopic taxonomic identification. Results indicated that the ROmembrane fed by the CPP fouled at least three times faster than the RO membrane fed by theFTP. The differential fouling between the two process streams was determined to be from lackof maintenance in the CPP influent piping that lead to the establishment of biologicalcommunities consisting of algae, microbes, and potentially fresh water clams. Thesecommunities produced low levels of natural polymers that when presented to the polyamide ROmembrane surface resulted in rapid fouling. Includes 21 references, tables, figures.

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Edition: Vol. - No. Published: 03/05/2003 Number of Pages: 15File Size: 1 file , 1.5 MB