The extent of dissolved ozone reacted with the wastewater sample was monitored through an ozone sensor. Reaction time of 60 seconds achieved good linear correlation between the extent of ozone degradation and the wastewater concentrations. The results showed that the rate and extent of ozone degradation are linearly proportional to the initial COD concentrations in range of 0-80 mg/L for the glucose- containing distilled water and canteen wastewater.