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A solar energy water purifier developed in Sweden holds the promise of providing clean, fresh drinking water to the estimated one-sixth of the world’s population that lacks it. The Sollvatten uses the ultraviolet (UV) light in sunshine to kill microrganisms in water, purifying as much as 11 liters of water in 2-6 hours, and can be used two to three times a day.
It’s estimated that lack of clean drinking water puts more than 1 billion people around the world at risk of water-borne bacterial dieseases such as cholera, dysentery, and typhoid. Recognizing the increasingly urgent strains being placed on water resources worldwide, the United Nations has declared 2013 the “International Year of Water Cooperation.”
Clean Water for the Masses
Solvatten is being recognized as a potentially revolutionary innovation in water purification by organizations around the world. Its design includes two 5-liter compartments with two transparent faces. When exposed to the sun, the water is heated to 130° F, high enough to kill off disease-causing pathogens. An indicator light turns from green to red, indicating when the water is safe to drink.
At last month’s World Water Week in Stockholm, the Sollvatten team demonstrated the portable water purification system’s effectiveness. They also shared other, significant benefits, including the social and economic empowerment it’s bringing to individuals and communities.
Charcoal, the primary household fuel used in Nairobi’s Kibera slum, is becoming increasingly scarce as a result of deforestation, which poses substantial and additional environmental and health problems in Kenya and numerous other countries around the world. The price of charcoal has risen sharply, adding an estimated 30%-50% to households’ fuel expenditures, as government authorities attempt to control and outlaw illegal logging, Sweden’s Global Utmaning reported following the World Water Week conference.
Joined by the Nordic Environment Ministers NDF and local NGOs, Sollvatten water purifiers are now in the hands of some 13,000 people in the area. Using it is enabling Nairobi families to save around $150 to $250 per year on energy costs, according to Global Autmaning’s report.
Yet more significantly, Sollvatten enables them to produce clean drinking water for their families much more easily at far less overall cost. Residents using Sollvatten are saving time and money, while also helping conserve precious forest and water resources. It’s also freeing up more time for them to pursue other ways of producing income.
In laboratory experiments, the ultra thin 1cm-by-2cm miniature tablet-like device, which was placed in a water container, killed 99.9% of bacteria in just 20 minutes, according to a study published last month in the Nature Nanotechnology journal by a team from Stanford University in California. "Researchers have always been looking for better ways to harvest sunlight for water disinfection. But traditional photocatalysts [using light to affect a chemical reaction] usually only use the UV part," said project leader Chong Liu, referring to ultraviolet rays, which are invisible to humans.
Liu's team developed a device that harnesses both ultraviolet rays and visible light at an unprecedented rate to kill harmful bacteria, and the results are "very promising", Liu told Al Jazeera. "The major advantage is that this material can harvest 50% of solar energy. This can greatly enhance the speed of water disinfection. It does not need any additional energy or effort for treating water," he said. Similar water purifying devices only harness UV rays, and take up to two days to work, according to the Swiss Federal Institute of Aquatic Sciences and Technology.
The device's main component is Molybdenum disulfide, Liu said, which is a silvery black compound similar in appearance and touch to graphite. Sunlight excites electrons in the device, which then react with water and oxygen to kill harmful bacteria, leaving pure water behind. Liu said the device has the potential to help people in countries hit by energy and water shortages. More than 660 million people lack access to potable water sources, and at least 1.8 billion people globally use a source of drinking water that is contaminated faecal matter, according to the United Nations.
Inadequate drinking-water and poor sanitation and hygiene are estimated to cause more than 840 000 diarrhoeal disease deaths each year,according to the World Health Organisation. More experiments on the device need to be carried out before it is ready for commercialisation, including conducting field tests, which is the next step, Liu, a postdoctoral scholar,said. "It can be a really simple point-of-use water disinfection device and can help a lot of people without access to clean water," he added. "The material itself is cheap and the synthesis process is facile. So we assume that the device would be of low-cost."
US scientists test tiny water purifier powered by light
Scale problem there. Also cost. But, yes, in large cooperative communities, a better solution.Nice piece of simple engineering.. Only weakness is the filter and it's replacements.
Would be even BETTER to use REAL Solar power to distill water in large community sized volumes. No filters required and potentially larger volumes...
