Microbial fouling of Reverse Osmosis (RO) membranes occurs when an imposed water flux is too high or the crossflow velocity is too low for a given bacterial concentration. Bacteria, being colloidal particles, will start to deposit onto the RO membrane when the critical flux and critical conversion are exceeded. Control of microbial fouling on RO membranes can be controlled by adjusting the flux to below the critical flux and conversion values.