Inactivation of Enterococcus sp. by photolysis and TiO2 photocatalysis with H2O2 in natural water

This paper presents research carried out into the disinfectant power of a series of treatments based on the individual application and possible combinations of TiO2 (1 g/L), H2O2 (0.04 mM) and irradiation (290–800 nm and 320–800 nm) on Enterococcus sp., a faecal bacterial indicator used in water analysis. The main aims are the determination of the influence of the UVB range on the inactivation of Enterococcus sp. in natural water, the mode of application of irradiation (intermittent or continuous) and the capacity of bacterial recovery after the application of the treatments in darkness conditions. The results show that when the irradiation includes the UVB range, a very high degree of inactivation is obtained in an Enterococcus sp. solution in natural water (N0 = 108 CFU 100 mL 1) by irradiation alone. Neither the addition of TiO2 nor of H2O2 are very relevant in these conditions. However, if the irradiation does not include the UVB range, the bactericidal action of photolysis is practically nonexistent, highlighting the positive effect of TiO2 and H2O2 on the irradiation, the photocatalysis and photocatalysis/H2O2 treatments obtaining a higher degree of disinfection. Continuous and intermittent illumination give rise to similar inactivation levels in all the treatments studied, except for photolysis in which a significant increase in inactivation is observed when the irradiation is continuous. During 3 h of darkness following application of the treatments, there is no change or else a slight recovery of the bacterial population. 2011 Elsevier Ltd. All rights reserved.