Ultraviolet Radiation for Microorganism Inactivation in Wastewater

The purpose of this research stream is to evaluate the kinetics of bacterial strains of Pseudomonas aeruginosa, to establish the influence of UV doses on the kinetics of disinfection, to study UV-resistant strains of Pseudomonas aeruginosa, and to underline the influence of suspended solids on the inactivation kinetics of these strains. Furthermore, and due to the lack of readily available information about the influence of temperature on microorganism inactivation processes subsequent to inactivation with UV radiation, a series of batch studies were performed at 5 ̊C, 25 ̊C, 37.5 ̊C and 50 ̊C. This paper investigates the impact of UV irradiation on bacterial strains of P. aeruginosa inactivation in both primary and secondary wastewater effluents and to show the influence of filtration in the process of disinfection of water by UV irradiaton. Our results indicate that the effect of temperature within the normal operating range of most treatment plants, i.e., 25 ̊C to 37.5 ̊C, was found to be not statistically significant on the kinetics of the UV disinfection process. However, the kinetics of the UV disinfection process was highly affected by system operating at extreme temperatures, i.e., at 10 and 50 ̊C. In a temperature range of 25 ̊C to 37.5 ̊C, the inactivation of P. aeruginosa strains varied according to the incubation time and did not exceed 4 U-Log. Consequently, having more than 10 organisms/100ml of P. aeruginosa in treated wastewater would cause serious health and environmental problems. Low inactivation was observed when the operating temperature was reduced to 10 ̊C regardless of the incubation time tested. In contrast, a considerable increase in the inactivation rate was noted when the temperature of the disinfected wastewater was increased to 50 ̊C. Hence, as 5 ̊C and 50 ̊C are outside the operating range of most treatment plants, as in our country, Tunisia, it is reasonable to assume that the effect of temperature change on the kinetics of UV disinfection process is negligible.