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Solar Water Disinfection: A Solar Solution to Water Pollution

Solar water disinfection offers a simple solution for purifying water

rkit / Pixabay

Access to safe drinking water is one of the biggest challenges facing developing countries. Because infrastructure is limited or non-existent, water is neither purified or delivered to households in many communities. Water is collected from local rivers and streams, which are typically also used for bathing. Very often the surrounding area is used for grazing livestock, which may wade into the water to drink. Consequently, the water is exposed to contamination by animal and human waste.

Drinking water that is contaminated with pathogenic micro-organisms results in the spread of water borne diseases such as cholera, dysentery, giardiasis, cryptosporidiosis, and other bacterial gastrointestinal infections, many of which are life-threatening, especially to vulnerable members of the population, such as infants, the elderly, and those with compromised immune systems. According to the UNICEF, 1.8 million people die from diarrhea related disease every year, with children from developing countries being primarily affected – a staggering 1.6 million children under the age of five, die from diarrhea every year, equating to the deaths of more than 4000 children every day. The majority of these deaths are related to poor sanitation and hygiene, and to drinking water contaminated with pathogens.

Ultra violet radiation has long been used in water disinfection processes at water purification plants in first world countries to kill disease causing micro-organisms. UV-A disrupts the metabolism, and breaks down the cell structure of pathogenic micro-organisms. It also causes chemical reactions within the oxygen contained in water to produce oxygen free radicals and hydrogen peroxide, which are highly effective at killing any pathogenic micro-organisms that may be present in the water. In addition, solar energy can be harnessed to heat up water, which will kill micro-organisms when the water temperature rises above 50°C, much the same as boiling water would, but without the need for electricity or fire.

Now, a basic form of this technology is being implemented in developing countries by harnessing ultra violet rays from the sun to disinfect drinking water through the solar water disinfection (SODIS) project. This simple method involves filling up plastic PET bottles with water and leaving to stand for six hours in the sun – on cloudy days this needs to be increased to two days. However, a new study conducted by researchers from the Johns Hopkins University School of Medicine, reveals that the treatment time can be drastically reduced by adding lime to the water, which speeds up the solar disinfection process significantly, making the water safe to drink in just thirty minutes.

Pictograms SODIS

A major factor in implementing these safe practices is educating communities, and providing them with the basic resources necessary to collect and treat water to make it safe for drinking. The SODIS project addresses this need, through the development and dispersal of educational resources to schools and NGO’s that work within impoverished communities throughout the world. Lesson plans on basic hygiene, sanitation, and how to collect, treat, and store drinking water to ensure that it is safe to drink, have been developed from the training manuals, and are being taught to school children at schools in Kenya and Bolivia.

A study conducted by Irish doctors on the health of Kenyan children using the SODIS method to provide safe drinking water has shown a distinct health benefit over children not drinking SODIS purified water, not only in terms of a decrease in diarrhea related illness, but they also exhibited enhanced physical development as a result of their improved health.

The SODIS method does have a few limitations. While it is extremely effective at removing disease causing micro-organisms from drinking water, it cannot remove chemical pollutants, heavy metals, or sediment, but by far the gravest health concern in developing countries is water contaminated with pathogens. As solar energy offers a cheap, simple, and effective way to remove pathogens, it can go a long way to improving the health standards of communities in third world countries without the need to boil water. More importantly, this simple method of water purification using solar energy can save thousands, if not millions of lives every year.

Nature provides all our needs – we simply need to look to nature to provide solutions to common problems.

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