CITRUS MAY BE KEY TO DRINKING WATER PURIFICATION

Water-related disease is a serious concern globally as many countries struggle to access to clean drinking water; however, new research published in the American Journal of Tropical Medicine and Hygiene suggests the humble lime may provide an inexpensive and quick method to purifying water.

Researchers at the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins School of Medicine have discovered adding lime juice to water treated with a solar disinfection method removes detectable levels of harmful bacteria such as Escherichia coli significantly faster than solar disinfection alone.

“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."

One method of using sunlight to disinfect water that is recommended by UNICEF is known as Solar water Disinfection (SODIS), which 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, the researchers looked at microbial reductions after exposure to both sunlight and simulated sunlight. They 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.

They found 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 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."