title: Modelling of reactivation after UV disinfection: effect of UV-C dose on subsequent photoreactivation and dark repair.
abstract: The increased use of UV radiation as a wastewater treatment technology has stimulated studies of the repair potential of microorganisms following treatment. In this study, samples of unfiltered secondary effluent were irradiated with seven levels of UV-C doses (50-200 mW s/cm(2)) from six low-pressure lamps in an open-channel UV disinfection system. Following irradiation, samples were incubated at 20 degrees C under photoreactivating light or in darkness. Samples were analysed for 240 min following incubation. The logistic model is proposed to explain the relation between photoreactivation and the UV-C dose received by the microorganisms. That model accurately fitted the data obtained in photoreactivation experiments, permitting interpretation of the estimated kinetic parameters: S(m) and k(2). In the experiments carried out in darkness, a slight reactivation is observed (<0.1%), followed by a decay period in which survival decreases. In order to model this last period, a modification was made to the logistic model by including a term of mortality that assumes a zero-order kinetic. The parameters S(m) and k(2), in both photoreactivation and darkness, show an exponential dependence on the UV-C inactivating dose. It is possible to predict their values, and hence the reactivation curve, from the equations proposed in this work.
authors.affiliation: Department of Chemical Engineering, Food Technologies and Environmental Technologies, Faculty of Marine and Environmental Sciences, University of Cádiz, Cadiz, Spain. enrique.nebot@uca.es
authors.forename: E
authors.initials: E
authors.lastname: Nebot Sanz
authors.forename: I
authors.initials: I
authors.lastname: Salcedo Dávila
authors.forename: J A
authors.initials: JA
authors.lastname: Andrade Balao
authors.forename: J M
authors.initials: JM
authors.lastname: Quiroga Alonso
mesh_terms: D004203:Disinfection; D007700:Kinetics; D050296:Microbial Viability / Q000528:radiation effects; D008954:Models, Biological; D010777:Photochemistry; D014466:Ultraviolet Rays