A disinfectant-resistant biofilm in a spacecraft potable water system can threaten system maintainability (microbially influenced corrosion/degradation) and crew health (pathogen survival). Iodine, while an effective disinfectant in low doses (ca. 2-4 mg/l) in bulk water, has been demonstrated to have limited effectiveness in controlling mixed aquatic biofilm in both bench-scale and large water reclamation tests. This report provides data on the feasibility of using ozone as an alternative or supplemental disinfectant.Tests were conducted in a biofilm testbed, a 20 liter bench-scale closed-loop recycling water system previously used for iodine disinfection studies. Ozone generated by ultraviolet irradiation of either air or pure oxygen was tested as a disinfectant on an iodine resistant biofilm. The results demonstrate that ozone is an effective disinfectant against an iodine resistant biofilm. Complete biofilm disinfection occurred using low level exposure to ozone (0.15 mg/l) in less than 6 hours, and higher level exposure (1.2 mg/l) in less than 10 min.