Using Limes and Synthetic Psoralens to Enhance Solar Disinfection of Water (SODIS): A Laboratory Evaluation with Norovirus, Escherichia coli, and MS2

Abstract

We investigated the use of psoralens and limes to enhance solar disinfection of water (SODIS) using an UV lamp and natural sunlight experiments. SODIS conditions were replicated using sunlight, 2 L polyethylene terephthalate (PET) bottles, and tap water with Escherichia coli, MS2 bacteriophage, and murine norovirus (MNV). Psoralens and lime acidity both interact synergistically with UV radiation to accelerate inactivation of microbes. Escherichia coli was ablated > 6.1 logs by SODIS + Lime Slurry and 5.6 logs by SODIS + Lime Juice in 30-minute solar exposures, compared with a 1.5 log reduction with SODIS alone (N = 3; P < 0.001). MS2 was inactivated > 3.9 logs by SODIS + Lime Slurry, 1.9 logs by SODIS + Lime Juice, and 1.4 logs by SODIS in 2.5-hour solar exposures (N = 3; P < 0.05). MNV was resistant to SODIS, with < 2 log reductions after 6 hours. Efficacy of SODIS against human norovirus should be investigated further.

Solar water disinfection (SODIS): A review from bench-top to roof-top

“…Safapour and Metcalf were unable to inactivate T2 phage after 8 h exposure to strong sunlight and reflector-boosted water temperatures of 62 • C [58]. Similarly Harding and Schwab were unable to induce any significant reduction in viable murine norovirus populations using UV-A light [59]. The indications are that viral pathogens may prove to be among the most resistant to solar disinfection.…”

Solar Disinfection of Viruses in Polyethylene Terephthalate Bottles

“…However, the use of PET bottles involves conducting laboratory experiments in large volumes of water (at least 500 ml for each experimental condition) and thus requires the preparation and handling of large quantities of viruses as well. To date, therefore, only a few investigators have conducted SODIS experiments using PET bottles such as those typically used in the field (7,12). To circumvent the need for large volumes, we compared the inactivation of MS2 in 0.5-liter PET bottles with that in 20-ml glass beakers placed inside 0.5-liter PET bottles exposed to our solar simulator.…”

“…SODIS has proven to be efficient at inactivating a wide range of bacteria under laboratory and field conditions and, more impor-tantly, at reducing the number of diarrhea cases in field surveys (5). However, studies on the inactivation of enteric viruses by SODIS are scarce, and even fewer studies have been conducted in PET bottles, simulating actual SODIS conditions (7,12). The available data are further complicated by the facts that (i) standardized experimental procedures for the study of SODIS are lacking and (ii) the solution conditions promoting virus inactivation by SODIS are mostly unknown and hence are not reported.…”

“…Additional interventions may be implemented to enhance the efficiency of the overall process. For instance, turbid water may be filtered prior to solar exposure, or bottles may be placed on a refracting surface (such as aluminum, or a roof made with corrugated iron sheets) (5,7,8). In addition to disinfecting the water, SODIS has the benefit of eliminating the need for a separate, potentially contaminated storage container.…”

Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation

“…Under the sunlight, MS2 can be inactivated to different extent depending on the exposure conditions (e.g., exposure time, irradiation intensity, and solution temperature) (Harding and Schwab, 2012). Fig.…”