The impacts of ozone dose in the formation of biodegradable dissolved organic carbon (BDOC) were studied at the North Bay Regional Water Treatment Plant (NBR). Increasing the ozone to total organic carbon ratio to 0.45 (mg/mg) resulted in the formation of BDOC. Sedimentation and filtration/adsorption were effective in removing BDOC to non-measurable levels prior to the water entering the distribution system. Data from an on-going distribution system monitoring program indicate no discernible adverse impacts on microbiological parameters from using ozone during water treatment. Heterotrophic plate count (HPC) levels were similar before and after the use of ozone. Maintaining chlorine residual levels above 0.3 mg/L appears to be important for controlling HPC levels.