dissolved ozone thereafter prefiltered water replaced di water the permeate from the membrane module was collected in a bottle with cap the reject water was either recycled or wasted several membranes constructed were tested to ascertain their fouling properties based on these results selected membranes were further studied to determine their ability to produce high quality water following preliminary screening to identify those membranes that had both adequate permeate fluxes and an appropriate mwco further investigations were conducted to determine the catalytic properties of the selected membranes and their resistance to fouling these experiments were conducted using the apparatus described in fig2 the experiments were conducted using natural waters for comparative purposes u201c control u201d experiments were conducted using commercial membranes and the same source water taken at the same time and location the removal of disinfection by products and their precursors were investigated using a combined ozonation nanofiltration system the results compare performance of the system using a commercial membrane and the same membrane coated with 20 or 40 layers of iron oxide nanoparticles 4 6 nm in diameter for the coated membranes the finished water showed significant improvement in the water quality as compared to that obtained with the uncoated membranes hydroxyl radicals produced at the iron oxide coated membrane surface as a result of ozone decomposition are believed to enhance the degradation of the nom and reduce the concentration of dbps and their precursors thus resulting in a decrease in the concentration of dbps formed increasing the number of.