An automated produced water treatment system that injects ozone or an ozone-oxygen mixture upstream of produced water separators, with the dose rate changing dynamically as the produced water quality changes, as determined by continuous monitoring of the produced water quality by a plurality of sensors that detect water quality parameters in real time. The system may operate as a “slipstream” injection system, that draws a portion of produced water from the produced water pipeline and injects ozone or an ozone-oxygen mixture back into the pipeline with disrupting or slowing normal operations. Disinfectants or other additives may also be injected. The treatment system may be wholly or partially contained in mobile containers or trailers, for on-the-fly use in existing produced water treatment facilities.