What is WADI
WADI is an easy-to-use and cost-effective UV measurement device for solar water disinfection (SODIS method). WADI is solar-powered, operates without the use of chemicals, batteries or filters and guarantees safe drinking water thanks to the power of the sun. WADI is a device developed to trace the progress of solar water disinfection in a PET-bottle by detecting and calculating the UV-A rays of the sun, indicated by a status bar and smiley face. WADI, building on the process of solar water disinfection to purify contaminated water, makes the method more attractive among end users by visualizing its results.
With its built-in solar cell, WADI is energy-self-sufficient, affordable and has a guaranteed life time of at least two years. The device can be used and shared by several persons and families since many bottles of water can be purified simultaneously. Internationally understandable pictograms on the device facilitate correct usage. WADI is not only meant to be a life-saving tool which satisfies basic human needs but also a lifestyle product which brings easy and inexpensive solar water disinfection to remote low-income households.
As a technological innovation, WADI facilitates the consumption of safe and clean water in an efficient and affordable way. On top of that, it improves health and environment and contributes to the Millenium Development Goals (MDGs) and the human rights (for more information, please refer to Goals.)
Solar water disinfection is approved by UN and WHO for being the simplest and cheapest water disinfection method.
How to use WADI
Solar water disinfection is a simple procedure by which to purify water: Contaminated water is filled into a transparent PET-bottle and exposed to sunlight for a certain amount of time, depending on the UV intensity. The UV radiation of the sun kills diarrhea-generating pathogens in the water. While the Swiss Federal Institute of Technology (ETH) Zurich recommends an exposure time of around 6 hours for the sun to completely purify the water, field trials conducted by Helioz have shown that the process may sometimes be much quicker, always depending on the varying weather conditions. Near the Eastern coast of Central India, for example, tests have shown that the microbiological disinfection may take as little as 45 minutes under bright sky and relative intense sun during the month of April. In case of cloudy skies and rain, ETH Zurich recommends an exposure time of up to 2 days.
As can easily be seen, the amount of time needed for the sun to purify the water may vary greatly and has been a crucial and unknown factor for end users until recently.
WADI is an innovative device that measures the UV radiation of the sun and in doing so calculates the duration of the disinfection process. As soon as enough radiation has hit the bottle, WADI lets the user know that the water is safe to drink. While until today, solar water disinfection has only been used by several million people worldwide, WADI has the potential to make solar water disinfection a widely used method around the world. By making the method calculable, visible and attractive for people in the lowest income bracket in developing countries, WADI is a live-saving tool that is not only affordable and durable, but also easy to use.
How to use WADI:
(1) Fill the PET-bottle with water.
(2) Screw WADI onto the bottle (like a bottle top).
(3) Push the reset button.
(4) Expose the set of PET-bottle and WADI to the sun.
(5) Wait for the sad face to turn into a smiley face.
(6) Water is ready for consumption.
WADI was designed for usage without much training. In most of the Southern countries, children and women who often cannot read nor write are responsible for procuring water. Helioz included self-explanatory pictograms on WADI that ensure easy implementation and enhance its usability.
Field trials, tests and usage in Africa (Ethiopia, Ghana, Kenya, Mozambique, Rwanda, South Africa, Uganda), Asia (India, Thailand), Latin America (Bolivia, Brazil) and Europe (Austria) have shown that WADI is easy to handle and that its usage is soon integrated in the daily routine. Furthermore, tests have shown that the use of WADI alleviates the daily chores of its users. Still, awareness building and behavior change are critical factors for spreading and fostering the use of this simple and cost-efficient tool on a sustainable and longterm basis.
Please note that for solar water disinfection, the contaminated water shall not be turbid. Make sure that the used PET-bottles are transparent, clean and unscratched and remove any labels before use.