A removable disposable air dryer cartridge is provided for a small enterprise water ozonation system. The cartridge includes an air inlet to receive atmospheric air, a desiccant material to remove moisture, and a dry air outlet for interfacing with the ozonation system to provide dry air to an ozone generator. This facilitates better ozonation of water in the system, since dry air reacts better in an ozone generator, achieving higher concentrations of ozone gas, thus resulting in a better “kill rate” when ozonated water is applied to bacteria. The air dryer can be provided as a chamber of a combined air dryer and water filter cartridge, the other chamber being a water filter chamber having a water filter for extracting large particles of material from the water stream in order to prevent damage to the system.