Modeling hydrodynamics and ozone residual distribution in a pilot-scale ozone bubble-diffuser contactor

Mixing conditions inside a pilot-scale ozone bubble-diffuser contactor and the effect of mixing on ozone residual concentrations were investigated. The 17-ft-high, 6-in.-diameter contactor was operated with both counter-current and cocurrent water and gas flows. When the contactor was operated in the cocurrent mode, it was packed with 1-in. plastic saddles. Tracer and ozonation tests showed that mixing conditions in the contactor ranged from nearly plug-flow to well mixed. Dispersion increased as the gas flow rate increased and as the water flow rate decreased, with the latter dependency being stronger. The lowest dispersions were observed for tests run with the cocurrent packed contactor. A computer model was developed and used to predict dispersion numbers, ozone concentration profiles, ozone residuals, and C × T parameters. Disagreements between observed and predicted tracer curves might have been caused by short-circuiting, but in general the model predicted ozone residuals well.