Water disinfection employing UV radiation combined with hydrogen peroxide

LABAS, M. D.; ZALAZAR, C. S.; BRANDI, R. J.; CASSANO, A. E.

Bilbao, España

Congreso; Chemical Reaction Engineering XI (CRE XI): Green Chemical Reactor Engineering; 2007

Microbiological contamination of waters is a problem demanding constant rate of studies to find solutions that should be efficient and, at the same time, signifying low cost and safe application technologies. Traditionally employed methods using chlorine are known to have some undesired secondary effects producing disinfection byproducts that should not be present in water for domestic use. During the last years Advanced Oxidation Technologies have been the subject of intensive studies and we have published some contributions concerning the kinetics of the application of UV radiation alone and Hydrogen Peroxide alone. This work is a continuation of the series employing a combination of both methods to investigate the possibility of a synergic effect between them. The test bacterium was Escherichia coli and the employed reactor was an isothermal, perfectly mixed, batch system in an annular space surrounding a germicide tubular lamp. Experiments were performed following the time evolution of the surviving bacteria, when the contaminated water with E. coli ATCC 8739 was subjected to different irradiating conditions employing two types of lamps (of 15 and 40 W) and neutral density filters and varying the hydrogen peroxide concentration between 15 and 300 ppm. A kinetic model was proposed that account for the effects of the hydrogen peroxide concentration and the absorbed radiation intensities. The model allows the evaluation of the initial bacteria resistance to the bacteriological action of the disinfectants. The parameters of the model and the corresponding reaction order to the inactivation of bacteria are obtained with a non linear multiparameter estimation comparing experimental results and predictions from the model. The dependence with hydrogen peroxide is not linear and the time lag is reduced when the hydrogen peroxide concentration is increased. UV radiation alone is much more effective than hydrogen peroxide alone. The synergic effect of the combination of both does not change significantly the previously observed results with UV alone.