UV ability to inactivate microorganisms combined with factors affecting radiation

Abstract

In the present study, the effect of UV radiation on the inactivation of a range of microorganisms was studied. Each organism was seeded into sterile tap water and exposed to UV in batch experiments with changing turbidities. In addition, the effect of UV on microbial communities in river Nile water was examined. It was found that 1min contact time (0.5L/min flow rate) was effective against vegetative cells levels almost reaching zero (except with Staphylococcus aureus). On the other hand, spore-forming bacteria, Candida albicans and coliphage were more resistant to UV. This contact time caused coenobia cells in single form with Scenedesmus obliquus while for Microcystis aeruginosa colonies broke into smaller groups. Exposure of Nile water microbial communities to UV showed that yeasts and Aeromonas survived better than the other organisms while in the phytoplankton partial fragmentation occurred in some algal groups. The protective effect of turbidity differed between organisms, with increased contact time under conditions of stable turbidity having no effect on the organisms. At 20 NTU the UV radiation had no effect on the morphological characters of algal cells. In reactivation experiments, it is clear that photoreactivation, and not dark repair, takes place with bacterial cells. Only coliphage had no photoreactivation and dark repair responses although with coliphage and host, both reactivation processes worked well. Moreover, the irradiated algae regained their normal shape after 3 days in suitable media and enough light.

Characterization of predominant bacteria isolates from clean rooms in a pharmaceutical production unit

“…These results are in agreement with the findings of other workers (Onaolapo, 1995). Shaban et al(1997) and Newcombe et al(2005) found that Staphylococcus and spore-forming Bacillus were more resistant to UV than the other vegetative bacteria. Ajaz et al(2004) screened 4 phenol resistant bacteria strains, two of which belong to genera Staphylococcus and Bacillus.…”

Field investigation of advanced oxidation of secondary effluent from municipal wastewater treatment plant

“…This value is less than the 5 mg L −1 TSS value, which is known to reduce Field investigation of advanced oxidation of secondary effluent 2051 the effectiveness of UV inactivation. [7,34] The color ranged from 40-50 hazen units, and the mean particle size of the sample was 30 µm with 86% greater than 10 µm. Assuming most of the color was attributed to organic substances, one can assert that absorption of UV photons by the organic matter in the secondary effluent had taken place during the irradiation.…”

Response of Different Strains of Enterococcus faecalis to UV Inactivation after Freezing

“…Applications of UV disinfection in water and wastewater treatment systems have increased in recent years in Canada. Numerous research has been carried out to find the correlations between water quality, bacterial sensitivity and UV disinfection efficiency [10]- [12], the impact of cold temperatures on UV disinfection processes, especially, the responses of the pathogenic microorganisms after experiencing freezing to UV is however seldom examined [13], [14]. As a treatment alternative, natural or mechanical freezing has been used for various water or wastewater treatment, sludge pre-treatment or conditioning, and desalination [15]- [19].…”