AWWA MTC57544

Extra-cellular polysaccharides (EPS), soluble microbial products (SMPs), and bacterial cells were isolated to observe their influence on the flux decline of nanofiltration (NF) systems which were challenged with these constituents raised on recalcitrant and readily degradable carbon sources (natural organic matter (NOM), SMPs and acetate). A resistance-in-series model, which related flux decline with membrane-associated polysaccharides was compiled and validated. Biofouling tests were conducted using bench-scale, flat-sheet membrane modules operated at 95 psi (6.7x105 Pa), pH = 7, and 21C. Increased membrane flux-decline was associated with an increase in surface EPS content where between 30-80% of the normalized flux decline corresponded to membrane-associated EPS content between 5.1 and 50 ug/cm2, respectively. During all tests performed with NOM and acetate, culturable biofilm cell densities showed no statistically significant difference (0.1x108 to 5x108 CFU/cm2) and were independent of EPS concentration. Results from resistance-in-series models suggest that flux decline was relatively insensitive to bacterial cell numbers and was governed by EPS associated with the membrane surfaces. Includes 30 references, table, figures.