Abstract: Apparatus for sanitizing water generally includes a line for receiving a flow of water and an injector assembly for introducing an ozone containing gas into the flow of water to produce a first ozonated water having an increased oxygen concentration relative to the flow of water being passed to the injector assembly. The apparatus further includes an electrolytic device, for example, an electrolytic chlorinator cell, positioned to receive the first ozonated water from the injector assembly. The electrolytic device is effective to produce, from the first ozonated water, a second ozonated water including one or more biocidally effective substances other than oxygen gas. The second ozonated water includes biocidally effective substances, for example chlorine, hydroxyl radicals, and/or other effective oxidizing substances.