Abstract: A water purification system which filters particulates from the water and treats organic contaminats with ozone. The incoming contaminated water flow is divided, with half passing through each of two filter and ozone contact systems. Initially, each stream is passed though a sand separation device to remove large high density particulate mater, then through a multi-stage filter arrangement incorporating disposable filter cartridges. Ozone is injected into each stream leaving the filter system. The flow passes through elongated plug-flow tubing to assure optimum water/ozone contact, then enters a multi-compartment secondary contactor having a series of perforated baffle plates through which the water flows to assure complete ozone/water contact. Finally, each stream passes through a final filter stage, then the streams are combined and pass to storage or a purified water outlet.