A flow of oxygen containing gas is irradiated with UV light to convert oxygen molecules to ozone molecules and produce an ozonated gas. Water to be treated is augmented with silver prior to entraining the ozonated gas in the water. The ozone enriched water containing silver is irradiated with UV light to produce hydroxyl radicals. Whereby, microorganisms are killed by the UV radiation, organic matter is oxidized by the ozone and the combination of silver and hydroxyl radicals prevent downstream growth of bio-film contamination.