Abstract: A method for treating water with ozone in which a countercurrent flow of liquids is established within a treatment vessel to insure intimate contact and substantial contact time between ozone and water. The ozone and water are first pre-mixed by passing the ozone through a diffuser into a moving stream of water and the mixture is circulated in a tortuous path through a coil and discharged at the end of the diffuser coil through a number of orifices into the lower portion of the treatment vessel in a generally upwardly and outwardly direction with respect to the vertical axis of the treatment tank. Treated water suitable for bottling and storage is withdrawn from the bottom of the treatment vessel at an elevation below that of the discharge orifices to establish a countercurrent flow between the incoming and outgoing fluids.