Scale-up of sonochemical reactors for water treatment

A novel pilot-plant scale sonochemical reactor (UES 4000 C Pilotstation) has been specifically developed for degrading a variety of water contaminants in large-scale applications. We report here the sonochemical degradation of three chemical compounds in aqueous solution: the chlorinated volatile contaminants dichloromethane (DCM) and trichloroethylene (TCE) and the nonvolatile azo dye methyl orange (MO). The flow-through reactor in the Pilotstation consists of four 612 kHz piezoelectric transducers which are driven by a power source operating at 3kW. The sonochemical reaction chamber has a volume of 6 L, while the total capacity of the Pilotstation, including a heat-exchanger unit and a reservoir tank varies from a minimum volume of 7.25 L to a maximum over 45 L. The observed reaction rates for the degradation of these contaminants in the Pilotstation were compared with values determined under similar conditions in small-scale bench reactors in order to evaluate its performance over a wide range of power densities. The pseudo-first-order degradation rate for TCE in the Pilotstation was found to be more than 4 times higher than corresponding smaller values measured in lab-scale reactors. Furthermore, the observed rates for DCM degradation also exceeded those of the small-scale reactors by factors from 3 to 7. The degradation rate of these two chlorinated compounds was faster with decreasing initial concentration in all cases. Experiments with 10 muM MO (aq) in the Pilotstation operating at different total volumes exhibited a linear dependence between the observed rate constants for sonolysis and the applied power density (PD), in the range 67 < PD (W/L) < 414. Steady-state . OH (aq) radical concentrations in each reactor were calculated and were shown to correlate with the applied power, density in the vessel. A power budget analysis for the Pilotstation indicates that nearly one-third of the applied power is converted in sonochemical activity.