Daily Archives: December 25, 2014

Evaluating SODIS in South Sudan

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

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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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Adsorption of MS2 on Oxide Nanoparticles

W Zhang, X Zhang. Adsorption of MS2 on oxide nanoparticles affects chlorine disinfection and solar inactivation Water Research 2015-02-01 69:59-67

Adsorption on colloidal particles is one of the environmental processes affecting fate, transport, viability or reproducibility of viruses. This work studied colloidal interactions (adsorption kinetics and isotherms) between different oxide nanoparticles (NPs) (i.e., TiO2, NiO, ZnO, SiO2, and Al2O3) and bacteriophage, MS2. The results shows that that all oxide NPs exhibited strong adsorption capacity for MS2, except SiO2 NPs, which is supported by the extended Derjaguin and Landau, Verwey and Overbeek (EDLVO) theory. Moreover, the implication of such colloidal interactions on water disinfection is manifested by the observations that the presence of TiO2 and ZnO NPs could enhance MS2 inactivation under solar irradiation, whereas NiO and SiO2 decreased MS2 inactivation. By contrast, all of these oxide NPs were found to mitigate chlorine disinfection against MS2 to different extent, and the shielding effect was probably caused by reduced free chlorine and free MS2 in the solution due to sorption onto NPs. Clearly, there is a pressing need to further understand colloidal interactions between engineered NPs and viruses in water to better improve the current water treatment processes and to develop novel nanomaterials for water disinfection.

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Electrochemical Disinfection of Drinking Water

Pavlović MG, Pavlović MM, Pavlović MM, Nikolić ND. Electrochemical Removal of Microorganisms in Drinking Water. International Journal of Electrochemical Science; 2014, Vol. 9 Issue 12, p8249-8262 

It is known that silver, even in small concentrations (hundred parts of milligrams per liter), has the ability to destroy microorganisms, i.e. it has strong bactericidal abilities. Cleansing vast amount of water using bactericidal ability of silver is usually performed in electrochemical way. The advantages of electrochemical disinfection process like: (a) environmental compatibility, (b) versatility to kill a wide variety of microorganisms under mild conditions, (c) no need for adding chemical medicines and (d) the benefits of in-situ generation greatly lower problems and dangers of usage gas chlorine in water disinfection, which is greatest during transport and storing of this disinfectant. Appliances for electrochemical disinfection of drinking water eliminate these faults of conventional disinfection methods. Medical researches show that excess of chlorine in water reacts with organic matter, leading to mutations and cancer formation in digestion organs and bladder. This paper represents research of successful microbiological disinfection of natural water that contains Acinetobacter, Pseudomonas aeruginisa, Sulfate-reducing clostridium, Streptococcus (F), Aeromonas, Citrobacter (F), Esherichia coli, Enterobacter (F) and Bacillus by water-disinfection appliance. This appliance can be used in water systems like water sorces, traps, reservoires, pools etc. (certificate of Clinical Center of Serbia).

SODIS UV Dosimetry Indicators

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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Pediatricians Have a Role in the Dental Health of Young Children

Segura A, Boulter S, Clark M, Gereige R, Krol DM, Mouradian W, Quinonez R, Ramos-Gomez F, Slayton R, Keels MA. Maintaining and improving the oral health of young children. Pediatrics 2014 Dec;134(6):1224-9. doi: 10.1542/peds.2014-2984.

Oral health is an integral part of the overall health of children. Dental caries is a common and chronic disease process with significant short- and long-term consequences. The prevalence of dental caries for the youngest of children has not decreased over the past decade, despite improvements for older children. As health care professionals responsible for the overall health of children, pediatricians frequently confront morbidity associated with dental caries. Because the youngest children visit the pediatrician more often than they visit the dentist, it is important that pediatricians be knowledgeable about the disease process of dental caries, prevention of the disease, and interventions available to the pediatrician and the family to maintain and restore health.

Click here for paper (Open Access).