Scale-up of sonochemical reactors for water treatment

A novel pilot-plant scale sonochemical reactor (UES 4000 C Pilotstation) ha s been specifically developed for degrading a variety of water contaminants in large-scale applications. We report here the sonochemical degradation o f three chemical compounds in aqueous solution: the chlorinated volatile co ntaminants dichloromethane (DCM) and trichloroethylene (TCE) and the nonvol atile azo dye methyl orange (MO). The flow-through reactor in the Pilotstat ion consists of four 612 kHz piezoelectric transducers which are driven by a power source operating at 3kW. The sonochemical reaction chamber has a vo lume 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 determine d under similar conditions in small-scale bench reactors in order to evalua te its performance over a wide range of power densities. The pseudo-first-o rder degradation rate for TCE in the Pilotstation was found to be more than 4 times higher than corresponding smaller values measured in lab-scale rea ctors. Furthermore, the observed rates for DCM degradation also exceeded th ose of the small-scale reactors by factors from 3 to 7. The degradation rat e of these two chlorinated compounds was faster with decreasing initial con centration in all cases. Experiments with 10 muM MO (aq) in the Pilotstatio n operating at different total volumes exhibited a linear dependence betwee n 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 conce ntrations in each reactor were calculated and were shown to correlate with the applied power, density in the vessel. A power budget analysis for the P ilotstation indicates that nearly one-third of the applied power is convert ed in sonochemical activity.