Photoinactivation of virus on iron-oxide coated sand: Enhancing inactivation in sunlit waters

Abstract

The goals of this study were to investigate the release of infective bacteriophages MS2 and FX174 (two human viral indicators) after adsorption onto an iron oxide coated sand (IOCS), and to promote viral inactivation by exploiting the photoreactive properties of the IOCS.The iron oxide coating greatly enhanced viral adsorption (adsorption densities up to w10 9 infective viruses/g IOCS) onto the sand, but had no affect on infectivity. Viruses that were adsorbed onto IOCS under control conditions (pH 7.5, 10 mM Tris, 1250 mS/cm) were released into solution in an infective state with increases in pH and humic acid concentrations. The exposure of IOCS-adsorbed MS2 to sunlight irradiation caused significant inactivation via a photocatalytic mechanism in both buffered solutions and in wastewater samples (4.9 log 10 and 3.3 log 10 inactivation after 24-h exposure, respectively). Unlike MS2, FX174 inactivation was not enhanced by photocatalysis. In summary, IOCS enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of one of the surrogates studied. These qualities make it an attractive option for improving viral control strategies in constructed wetlands. ª 2012 Elsevier Ltd. All rights reserved. IntroductionControlling the transmission of waterborne viruses is made difficult by the fact that viruses are incompletely removed through conventional treatment processes. Their small size helps them to bypass physical removal treatments such as sedimentation and conventional filtration (Symonds et al., 2009;Thompson et al., 2003). Even when associated with particles, viruses tend to remain in suspension and pass through granular media filters (Rao et al., 1984;Templeton et al., 2005). They also exhibit higher resistance to many disinfectants compared to other pathogens, including chlorine and UV (LeChevallier, 2004;Thompson et al., 2003). Thus, alternative processes are needed to supplement conventional removal and inactivation strategies. Natural treatment systems, such as constructed wetlands, have shown potential for virus removal. Viruses tend to adsorb poorly onto sand (Bales et al., 1991(Bales et al., , 1993, which is commonly used as wetland matrix (Brix and Arias, 2005;Hoffmann et al., 2011). The presence of metal oxides can greatly enhance adsorption. The positively-charged metal oxide surfaces naturally present on sands and soils offer favorable sites for the adsorption of negatively charged viruses and other pathogens. Similarly, pure metal oxides or * Corresponding author. Tel.: þ41 (0) 21 693 0891; fax: þ41 (0) 21 693 8070.E-mail address: tamar.kohn@epfl.ch (T. Kohn).Available online at www.sciencedirect.com j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s w a t e r r e s e a r c h 4 6 ( 2 0 1 2 ) 1 7 6 3 e1 7 7 0 0043-1354/$ e see front matter ª

Inactivation of MS2 coliphage in sewage by solar photocatalysis using metal-doped TiO2

“…The same action has been recorded when disinfection is referred to bacterial populations [21]. However, based on our results and in accordance to other studies, photocatalysis proved to be effective method for wastewater disinfection in artificial and natural conditions [6,27]. Additional asset of this technique is the fact that it may contribute in reducing the precursors responsible for the formation of disinfection by-products (DBPs), which are often produced, especially if wastewater disinfection practice involves chlorination [27].…”

“…However, it should be noted that the solar irradiation alone, without the addition of any catalyst, reduced the amount of colony forming endospores causing detrimental damages to the cells [13]. In the case of MS2 phages, the resistant nature of the virus requires significant high periods, which in certain cases may reach 24 h in order to observe a 4 Log decay with sunlight exposure [6]. Apart from the light intensity dependence, there are other factors that may differentiate the course of the process, of which the composition is enlisted among the most determinants.…”

Biosensors for waterborne viruses: Detection and removal

“…This is due mainly to the unique properties of viruses, such as their small size making them difficult to filter (~20-90 nm), as well as their increased resistance too many disinfection techniques that are routinely used to kill other pathogens. Because of these challenges, there is greater focus on developing more sophisticated methods for removing viruses from water [19][20][21][22]. Virus filtration is generally reliable for virus removal, but there are many issues to consider when designing a novel retention filter.…”

Fate of Environmental Pollutants

“…In addition, semiconductor photocatalysis was also suggested as an efficient technology for disinfection of water and wastewater (Robertson et al, 2012). Moreover, Pecson et al (2012) demonstrated that iron oxide coated sand enhanced the separation of viruses from the water column, and additionally provided a photocatalytic mechanism to promote inactivation of viruses in constructed wetlands.…”