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The removal of disinfection byproducts and their precursors was investigated using a combined ozonation-ultrafiltration system. A commercial membrane was coated 20 or 40 times with iron oxide nanoparticles (4-6 nm in diameter). With this membrane, the concentration of dissolved organic carbon was reduced by >85% and the concentrations of simulated distribution system total trihalomethanes and simulated distribution system halo acetic acids decreased by up to 90% and 85%, respectively. When the coated membrane was used, the concentrations of aldehydes, ketones, and ketoacids in the permeate were reduced by >50% as compared to that obtained with the uncoated membranes. Hydroxyl or other radicals produced at the iron oxide coated membrane surface as a result of ozone decomposition are believed to have enhanced the degradation of the natural organic matter, thereby reducing the concentration of disinfection byproducts. While increasing the number of times the membrane was coated from 20 to 40 did not significantly reduce the concentrations of most of the parameters measured, it did result in a significant decrease in the concentrations of ozonation byproducts. Increasing the sintering temperature from 500 to 900 degrees C also resulted in an improvement in the removal of the ozonation byproducts.

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The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900 C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, $50%, $86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.