MODELING INDUSTRIAL WASTE-WATER OZONATION IN BUBBLE CONTACTORS .2. SCALE-UP FROM BENCH TO PILOT-PLANT

A kinetic model constituted by ozone mol balance equations bath in the gas and in the water phases and a total mole balance equation has been applied to predict concentrations of dissolved ozone, C-03, ozone partial pressure at the reactor outlet, P-O30, and remaining chemical oxygen demand, COD, for the ozonation of two Industrial wastewaters released from distillery and tomato processing plants. Kinetic equations for ozone absorption rate present in the model were derived from the application of film theory to an irreversible gas-liquid reaction. Parameters involved in the model, reaction rate and mass transfer coefficients, Henry's law constant, etc., were estimated from bench-scale experiments. The model was applied to ozonation in bubble contactors of height/diameter ratio equal to that of the bench scale contactor and to a pilot plant bubble column of a height/diameter ratio about 3.6 times higher. The results showed good agreement with the experimental values when applied to contactors of the same height/diameter ratio. Deviations were less than 5%, 10% and 10% for COD, C-03 and P-O30, respectively. Similar deviations also were found when the model was applied to ozonation in the bubble column for reaction times higher than 15 minutes. For the short initial reaction period, deviations were much higher, possibly due to uncorrected values of mass transfer and reaction rate coefficients, the latter especially in the ozonation of tomato wastewaters. In all cases, however, the model predicts very well the experimental oxidation and ozone efficiencies. For these cases, deviations were lower than +/- 3%.