Not just good for cocktails: The secret to safe drinking water is a twist of lime and a bit of sun

With all the benefits of first world living, it is sometimes easy to forget that for billions of people getting hold of clean water to drink is still a problem.

For people living in less developed countries, their only source of water may be a spring or river - and it can often be infected with all kinds of nasty bugs.

Well now there is new hope thanks to a team of scientists who have found that water can be made safer by simply adding a twist of lime and leaving it out in the sun.

Secret of clean drinking water: A twist of lime and a bit of sun significantly cuts the the amount of dangerous bacteria in water

They found that this method removed detectable levels of harmful bacteria like Escherichia coli (E. coli) significantly faster than solar disinfection alone.

In low-income regions, solar disinfection is one of several household water treatment methods used to slash the risks of infection from dirty water.

One method of using sunlight to disinfect water that is recommended by Unicef is known as SODIS (Solar water Disinfection).

The SODIS method requires filling 1 or 2 litre 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 researchers from the Johns Hopkins School of Medicine 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.

Results showed a significant reduction in the levels of both E. coli and MS2 bacteriophage after solar disinfection when either lime juice or lime slurry was added to the water compared to solar disinfection alone.

But they did find that noroviruses were not dramatically reduced using this technique, indicating it is not a perfect solution.

A woman carries water to her home in the northern Central African Republic: Finding clean, safe drinking water is still a problem for billions

Professor Kellogg Schwab, director of the Johns Hopkins University Global Water Program said: '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.

'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 millilitres of juice per 2 litres of water amounts to about one-half Persian lime per bottle, a quantity that will likely not be prohibitively expensive or create an unpleasant flavour.'

Writing in the April 2012 issue of American Journal of Tropical Medicine and Hygiene the researchers said: '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]