A portable ozone test unit was designed and built for use in treating liquid materials with ozone. Due to its powerful oxidation properties, ozone has a great deal of potential as a treatment system for liquid waste materials and water supplies. The portable test unit was constructed so that is could easily be transported to a field site for testing. Several applications used the ozone test unit. The dark brown, odorous wastes effluent from a kraft pulp mill could be satisfactorily decolorized and deodorized by the ozone. In addition, the material after ozonation was more biodegradable than before ozonation. The ozone test unit was also used to treat potable water supplies to remove iron and manganese and to reduce off odors and tastes. (Author Modified Abstract)