Aqueous phase disinfection with power ultrasound: Process kinetics and effect of solid catalysts

The effectiveness of power ultrasound as a viable alternative for destroyin g pathogenic organisms in homogeneous and heterogeneous mixtures of aqueous solutions was investigated. The method involved monitoring of total colifo rm bacteria during sonication of E, coli suspensions in the absence and pre sence of equivalent mass concentrations of ceramic, metallic zinc, and acti vated carbon. It was found that disinfection by ultrasound is accelerated w ith solids in the order activated carbon > ceramic > metallic zinc. Process kinetics for each test system were assessed by nonlinear regression analys is of bacterial density vs time data, and the predicted model was found to resemble a well-known expression describing chlorination kinetics. The mode l denoted that in the presence of activated carbon the process rate was pse udo first order, and the required contact time to accomplish 50% kill was 2 .8, 2.4, and 4 times shorter than it was in the zinc-catalyzed, ceramic-cat alyzed, and noncatalyzed systems, respectively. It was further found that c atalytic effects faded away with increased sonication time and/or reduced n umber of bacteria, denoting(i) decreased probability of bacterial contact w ith the solid-liquid interface; (ii) erosion of solid surfaces by vibration al effects; and (iii) reduced cavity formation due to degassing effects of ultrasound.