Interaction between E-coli inactivation and DBP-precursors - dihydroxybenzene isomers - in the photocatalytic process of drinking-water disinfection with TiO2

The common drinking water disinfection procedures lead to the formation of disinfection by-products (DBPs), which come mainly from naturally occurring organic compounds disinfection by-products precursors (DBPPs). Solar disin fection by photocatalysis is a promising method, which could be applied to a drinking water treatment process in order to destroy a bacterial populati on and DBPPs as well. The complete E, coli inactivation by light irradiatio n over TiO2 suspension was reached in 20 min, while by light alone it was i n 70 min. Illumination was produced by a Hanau Suntest lamp simulating natu ral radiation power of 80 mW cm(-2). The addition of DBPPs like C6H4(OH)(2) : hydroquinone, resorcinol and catechol to bacterial suspension contained T iO2, resulted in a decrease in sunlight germicidal activity. A correlation between photoreactivity of dihydroxybenzene isomers and photocatalytic bact erial disinfection was demonstrated. Experiments performed under dark condi tions demonstrated either C6H4(OH)(2) or TiO2 separately do not affect to a large extent the survival of E. coli, while mixing of both showed a bacter ial deactivation between two- and one-order of magnitude in the presence of substances within 2 h. The order of decay in photodegradability was resorc inol > catechol, hydroquinone. The evolution of C6H4(OH)(2) degradation und er light in the presence of both oxygen and H2O2 as electron acceptor was d iscussed. (C) 2001 Elsevier Science B.V. All rights reserved.