Biodegradable organic matter (BOM) that is not removed during water treatment can potentially lead to the proliferation of bacteria along the distribution system, which can deteriorate the water quality, accelerate corrosion rates of pipes, and potentially increase the incident of bacteriological diseases. The main objective of this project was to collect and analyze full-scale system data on long-term responses to the implementation of ozonation with respect to its impact on bacterial regrowth potential as quantified by AOC and BDOC. One of the major observations over the sampling period was that ozonation caused a significant increase in the AOC concentration of the distribution system (over 100% increase) in spite of a low DOC source water. The use of ozone also caused a significant increase in the bacterial counts of the distribution system. In contrast, ozonation impacted BDOC and DOC only slightly compared to the impact on AOC concentrations, but this may have been because the source water had a low DOC and BDOC (1.2 and 0.11 mg/L, respectively). Includes 14 references, figures.