Ryberg EC, Chu C, Kim JH. Edible Dye-Enhanced Solar Disinfection with Safety Indication. Environ Sci Technol. 2018 Nov 20;52(22):13361-13369. doi: 10.1021/acs.est.8b03866.
The rural developing world faces disproportional inequity in drinking water access, where point-of-use water treatment technologies often fail to achieve adequate levels of pathogen removal, especially for viruses. Solar disinfection (SODIS) is practiced because of its universal applicability and low implementation cost, though the excessively long treatment time and lack of safety indication hinder wider implementation. This study presents an enhanced SODIS scheme that utilizes erythrosine-a common food dye-as a photosensitizer to produce singlet oxygen for virus inactivation and to indicate the completion of water disinfection through photobleaching color change. Experimental results and predictions based on global solar irradiance data suggest that over 99.99% inactivation could be achieved within 5 min in the majority of developing countries, reducing the time for SODIS by 2 orders of magnitude. Preserving the low cost of traditional SODIS, erythrosine embodies edible dye-enhanced SODIS, an efficient water disinfection method that could potentially be used by governments and non-governmental organizations to improve drinking water quality in rural developing communities.
Castro-Alférez M, Polo-López MI, Fernández-Ibáñez P. Intracellular mechanisms of solar water disinfection. Science Reports. 2016 Dec 2;6:38145. doi: 10.1038/srep38145.
Solar water disinfection (SODIS) is a zero-cost intervention measure to disinfect drinking water in areas of poor access to improved water sources, used by more than 6 million people in the world. The bactericidal action of solar radiation in water has been widely proven, nevertheless the causes for this remain still unclear. Scientific literature points out that generation of reactive oxygen species (ROS) inside microorganisms promoted by solar light absorption is the main reason. For the first time, this work reports on the experimental measurement of accumulated intracellular ROS in E. coli during solar irradiation. For this experimental achievement, a modified protocol based on the fluorescent probe dichlorodihydrofluorescein diacetate (DCFH-DA), widely used for oxidative stress in eukaryotic cells, has been tested and validated for E. coli. Our results demonstrate that ROS and their accumulated oxidative damages at intracellular level are key in solar water disinfection.
Posted in Disinfection
A very comprehensive review. But what happened to Part 1?
Stefanos Giannakis, Marıa Inmaculada Polo Lopez, Dorothee Spuhler, Jose Antonio Sanchez Perez, Pilar Fernandez Ibanezbc, Cesar Pulgarin, Solar disinfection is an augmentable, in situ-generated photo-Fenton reaction—Part 2: A review of the applications for drinking water and wastewater disinfection, Applied Catalysis B, Environmental http://dx.doi.org/10.1016/j.apcatb.2016.06.007
This is the second part of a comprehensive review article about photo-Fenton reaction at near-neutral pH used for water and wastewater disinfection. In this part, a critical revision of the fundamental physical, chemical and biological parameters affecting the photo-catalytic process efficiency are discussed. The effects of the chemical aspects, considered either as facilitators or competitors of photoFenton are deeply analyzed, with special focus on organic matter and its effect over bacterial inactivation. The role of solubilized iron and the biological nature of different pathogens are deeply assessed according to reported experimental data. Water temperature, turbidity, and radiation parameters like solar UV energy, ligh scattering and absorption during photo-Fenton are pictured in terms of treatment efficiency and suitable reactor design. Recent unconventional photo-Fenton strategies using iron chelates, iron oxides (including zero valent iron) and iron-based materials are also highlighted as new approaches to this process. Finally, the existing pilot scale studies in real conditions using photo-Fenton at near-neutral pH are revised, while alternative options and further research for real implementation are proposed.
Posted in Disinfection
McGuigan KG, Conroy RM, Mosler HJ, du Preez M, Ubomba-Jaswa E, Fernandez-Ibañez P. Solar water disinfection (SODIS): a review from bench-top to roof-top. Journal Of Hazardous Materials 2012 Oct 15; Vol. 235-236, pp. 29-46
Solar water disinfection (SODIS) has been known for more than 30 years. The technique consists of placing water into transparent plastic or glass containers (normally 2L PET beverage bottles) which are then exposed to the sun. Exposure times vary from 6 to depending on the intensity of sunlight and sensitivity of the pathogens. Its germicidal effect is based on the combined effect of thermal heating of solar light and UV radiation. It has been repeatedly shown to be effective for eliminating microbial pathogens and reduce diarrhoeal morbidity including cholera. Since 1980 much research has been carried out to investigate the mechanisms of solar radiation induced cell death in water and possible enhancement technologies to make it faster and safer. Since SODIS is simple to use and inexpensive, the method has spread throughout the developing world and is in daily use in more than 50 countries in Asia, Latin America, and Africa. More than 5 million people disinfect their drinking water with the solar disinfection (SODIS) technique. This review attempts to revise all relevant knowledge about solar disinfection from microbiological issues, laboratory research, solar testing, up to and including real application studies, limitations, factors influencing adoption of the technique and health impact.
Dawney B, Cheng C, Winkler R, Pearce JM. Evaluating the geographic viability of the solar water disinfection (SODIS) method by decreasing turbidity with NaCl: A case study of South Sudan. Applied Clay Science Volume 99, September 2014, Pages 194–200
While the solar water disinfection (SODIS) method of treating microbiologically contaminated water at the household level has proven to be effective at reducing incidence of diarrhea, its effectiveness is limited to waters of low turbidity. This study investigates the use of table salt (NaCl) to reduce turbidity in water containing dispersed colloidal clay particles as a means of expanding the user base of SODIS. Jar tests were performed on solutions of a low-activity clay, simulating the general composition of soils of the Vertisol type, which are found in key developing regions. Results show that dispersions exhibited as high as 92% particle removal efficiency. The results of this study suggest that NaCl in combination with as little as 30% bentonite by mass may be used to produce a small-scale jumpstart effect by reducing turbidity to a level suitable for SODIS treatment. Soil type was mapped and overlaid with population estimates in a GIS environment to highlight geographic areas where salt+SODIS may be most viable in the case study of South Sudan. Findings suggest that the NaCl method could expand access to SODIS technology by about 1.56 million people who currently lack access to an improved water source in the case study.
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K Lawrie, A Mills, M Figueredo-Fernández, S Gutiérrez-Alfaro, M Manzano, M Saladin. UV dosimetry for solar water disinfection (SODIS) carried out in different plastic bottles and bags. Sensors & Actuators B: Chemical. Mar2015, Vol. 208, p608-615.
Solar water disinfection (SODIS) is a well-established inexpensive means of water disinfection in developing countries, but lacks an indicator to illustrate its end-point. A study of the solar UV dosage required for SODIS, in order to achieve a bacteria concentration below the detection limit for: Escherichia coli, Enterococcus spp. and Clostridium perfringens , in water in PET bottles, PE and PE/EVA bags showed disinfection to be most efficient in PE bags, with a solar UV (290–385 nm) dose of 389 kJ m −2 required. In parallel to the disinfection experiments, a range of polyoxometalate, semiconductor photocatalysis and photodegradable dye-based solar UV dosimeter indicators were tested under the same solar UV irradiation conditions. All three types of dosimeter produced indicators that largely and significantly change colour upon exposure to 389 kJ m −2 solar UV; further indicators are reported which change colour at higher doses and hence would be suitable for the less efficient SODIS containers tested. All indicators tested were robust, easy to use and inexpensive so as not to add significantly to the attractive low cost of SODIS. Furthermore, whilst semiconductor photocatalyst and photodegradable dye based indicators are disposable, one-use systems, the polyoxometalate based indicators recover colour in the dark overnight, allowing them to be reused, and hence further decreasing the cost of using indicators during the implementation of the SODIS method.
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