Measurement of the 254 nm absorption of organics was chosen for monitoring the ozonation processes used to remove organic matter in a drinking water because of its ability to reflect the performance of ozonation. Ozone flow rate, ozone concentration in the gas (phase, addition of H202and seasonal variations on kinetics of the reduction of UV absorption were varied and the efficiency of ozonation was determined. For several yearst ozonation has been applied at different points in potable water treatment. The original goal of ozonation was reduction in taste and odor and disinfection without by products of organoleptic concern (e.g.. chlorophenols). Ozone also has the capacity to oxidize organic matter.