Sunlight Plus Lime Juice Makes Drinking Water Safer
— Looking for an inexpensive and
effective way to quickly improve the quality of your drinking water? According
to a team of researchers from the Johns Hopkins Bloomberg School of Public
Health and the Johns Hopkins School of Medicine, sunlight and a twist of lime
might do the trick. Researchers found that adding lime juice to water that is
treated with a solar disinfection method removed detectable levels of harmful
bacteria such as Escherichia coli (E. coli) significantly faster than
solar disinfection alone.
The results are featured in the
April 2012 issue of American Journal of Tropical Medicine and Hygiene.
"For many countries, access to
clean drinking water is still a major concern. Previous studies estimate that
globally, half of all hospital beds are occupied by people suffering from a
water-related illness," said Kellogg Schwab, PhD, MS, senior author of the
study, director of the Johns Hopkins University Global Water Program and a
professor with the Bloomberg School's Department of Environmental Health
Sciences. "The preliminary results of this study show solar disinfection
of water combined with citrus could be effective at greatly reducing E. coli
levels in just 30 minutes, a treatment time on par with boiling and other
household water treatment methods. In addition, the 30 milliliters of juice per
2 liters of water amounts to about one-half Persian lime per bottle, a quantity
that will likely not be prohibitively expensive or create an unpleasant
flavor."
In low-income regions, solar
disinfection of water is one of several household water treatment methods to
effectively reduce the incidence of diarrheal illness. One method of using
sunlight to disinfect water that is recommended by the United Nations
Children's Fund (UNICEF) is known as SODIS (Solar water Disinfection). The
SODIS method requires filling 1 or 2 L polyethylene terephthalate (PET plastic)
bottles with water and then exposing them to sunlight for at least 6 hours. In
cloudy weather, longer exposure times of up to 48 hours may be necessary to
achieve adequate disinfection. To determine if one of the active constituents
in limes known as psoralenes could enhance solar disinfection of water, Schwab
and Alexander Harding, lead author of the study and a medical student at the
Johns Hopkins School of Medicine, looked at microbial reductions after exposure
to both sunlight and simulated sunlight. The researchers filled PET plastic
bottles with dechlorinated tap water and then added lime juice, lime slurry, or
synthetic psoralen and either E. coli, MS2 bacteriophage or murine
norovirus. Researchers found that lower levels of both E. coli and MS2
bacteriophage were statistically significant following solar disinfection when
either lime juice or lime slurry was added to the water compared to solar
disinfection alone. They did find however, that noroviruses were not
dramatically reduced using this technique, indicating it is not a perfect
solution.
"Many cultures already practice
treatment with citrus juice, perhaps indicating that this treatment method will
be more appealing to potential SODIS users than other additives such as TiO2
[titanium dioxide] or H2O2[hydrogen peroxide]," suggest the authors of the
study. However, they caution, "additional research should be done to
evaluate the use of lemon or other acidic fruits, as Persian limes may be
difficult to obtain in certain regions."
The research was supported in part
by the Osprey Foundation of Maryland, The Johns Hopkins University Global Water
Program, the Johns Hopkins University School of Medicine Dean's Funding for
Summer Research and the Johns Hopkins University School of Medicine Scholarly
Concentrations.
ScienceDaily
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