Disinfection of water and wastewater by UV-A and UV-C irradiation: application of real-time PCR method

Abstract

PapersPerformance of the photo-Fenton process in the degradation of a model azo dye mixture J. Macías-Sánchez et al., Photochem. Photobiol. Sci., 2011, 10 The disinfection efficiency of synthetic and real wastewater by means of UV-A and UV-C irradiation in the presence or absence of TiO 2 was investigated. A reference strain of Escherichia coli suspended in sterile 0.8% (w/v) NaCl aqueous solution was used as a synthetic wastewater, while real wastewater samples were collected from the outlet of the secondary treatment of a municipal wastewater treatment plant. E. coli inactivation was monitored both by the conventional culture technique and by the real-time PCR method. Culture method showed that UV-C irradiation (11 W lamp) achieved total E. coli inactivation of 100% within 3 min of photolytic treatment. On the other hand, UV-A (9 W lamp)/TiO 2 ; [TiO 2 ] = 200 mg L -1 (i.e. best operating conditions) required 60 min to achieve total disinfection of the synthetic wastewater. Real time PCR revealed compatible results, regarding the better efficiency of UV-C. However, it showed different times of bacterial inactivation, probably due to the phenomenon of "viable but not culturable bacteria". Disinfection durability tests in the dark and under natural sunlight irradiation showed that there is cell repair when UV-C irradiation is used for synthetic wastewater disinfection. Regarding real wastewater it was observed that only UV-C irradiation was capable of totally inactivating E. coli population in short time. Comparing results obtained from both methods, real time PCR proved to be more reliable and accurate, concerning the bacterial detection and enumeration in aquatic samples after the application of UV irradiation.

Simultaneous removal of estrogens and pathogens from secondary treated wastewater by solar photocatalytic treatment

“…This behaviour has been observed several times from our group in the degradation of organic compounds by heterogeneous photocatalysis (Frontistis et al, 2012a, Frontistis et al, 2012b and photocatalytic disinfection (Chatzisymeon et al, 2011).…”

“…In recent years, various studies have been conducted to demonstrate photocatalytic disinfection under visible light, using mostly E. coli as a model microorganism, which is the well known bacterial indicator of faecal pollution Suri et al, 2012;Chatzisymeon et al, 2011;Dalrymple et al, 2010;Gamage and Zhang, 2010;McCullagh et al, 2007), however, the majority of studies focus strictly on the removal of E. coli without considering the presence of other emerging contaminants. Hence, this work reports the efficacy of solar TiO 2 -mediated photocatalytic process to remove simultaneously EE2 and E. coli from secondary treated wastewaters.…”

Synergistic Water-Treatment Reactors Using a TiO2-Modified Ti-Mesh Filter

“…Since the structures of Qβ and FCV, compared to E. coli and L. pneumophila, are simpler, Qβ and FCV were . In addition, the germicidal effect of UV-C is critical for disinfection [38,39]. On the contrary, VUV and UV-A are less important for it than the UV-C [40].…”

“…These results were also ascribed to the synergistic effect of photocatalysis and ozonation as mentioned in Section 3.3. In addition, the germicidal effect of UV-C with the formation of pyrimidine dimers in the DNA is critical for disinfection [38,39]. On the contrary, VUV and UV-A are less important for sterilization than the UV-C [40].…”

Selecting a Sustainable Disinfection Technique for Wastewater Reuse Projects

“…This is because of its ability to inactivate a wide range of pathogens without the formation of harmful byproducts [29]. In ultraviolet disinfection, water is exposed to short wave ultraviolet light.…”