Abstract: Water may be purified and treated to kill and/or remove various harmful contaminants and microorganisms with a method and system including ozone treatment and oxygenation. In the present system and method, the ozone treatment and oxygenation process is carried out in the chamber of one canister and includes one or two further canisters, either a pre-filtration canister that contains a filter for removing large particulates that might interfere with the ozone treatment and oxygenation process, or a post-filtration canister that contains a filter for removing smaller particulates downstream, or both. The system is versatile in that one or the other of the filtration canisters can be eliminated. To limit the expense of manufacturing the system, the exterior of the canisters are identically molded and the bottom caps of the canisters are integrally molded to the body of the canisters, also eliminating one possible leakage point.