A mobile water treatment system is disposed on a trailer of a truck. There is an intake filter, an intake hose, a pump or multiple pumps for water intake and sending water throughout the system, a filtering section that may include sand and/or bag filter or other types of filters, an ozone treatment section after the filters, a holding tank after the ozone section, a UV treatment section after the holding tank, and a chlorination tank. The water may then be sent to a water storage facility or other place as desired. The system includes a generator for power to run the system, and a controller for the system. The ozone section makes use of a misting nozzle in order to increase ozone contact time, and decrease ozone breakdown. The UV section makes use of a slightly downward tilted table with UV bulbs and reflectors above it, and preferably is mounted on a leveling system. A method of treating water uses the mobile system.