WADI Solar Disinfection System
WADI is a solar powered UV measurement device that determines when solar water disinfection (SODIS) occurs in PET bottles.
WADI is a device that measures radiation levels while water is placed under the sun in PET bottles. A happy smiley face in the display indicates the point at which the water has been in the sun long enough to kill bacteria.
Global regions which receive adequate sunlight
Solar water sterilizer Solvatten
Goal 6: Clean water and sanitation
WADI is manufactured by Helioz GmbH in Austria
5000 units distributed as of 2013.
WADI continuously measures the sun’s radiation and compares these measurements with scientifically tested data. As soon as the incident UV-dose reaches that of the reference value stored in WADI, the device indicates happy face.
WADI is water resistant, dustproof and is of size of a hand. The reset button on top of the WADI must be pressed during exposure to sunlight. A sad face along with one flashing bar will appear. Over time, a second, third and fourth bar will appear along with a sad face. Once WADI and the nearby water has received sufficient UV radiation, the sad face will turn happy along with 4 constant progress bars.
Minimum two years based on normal handling.
WADI is free of any toxic substances and does not change the taste or appearance of water.
WADI has been tested in various independent laboratories across Europe, Africa and Asia. SODIS technology is developed by ETH Zurich.
One of the research teams of BOKU scientifically certified the applicability of WADI.
Some basic safety measures are:
- SODIS cannot be used for water with turbidity higher than 30NTU, polluted with water or harmful chemicals.
- Only PET bottles are recommended for the use of WADI and SODIS.
- Use of corrugated iron sheet for SODIS is highly recommended for better performance.
- Regular cleaning of the solar cell and UV sensor is required to gaurantee adequate energy supply and correct measurements.
Methods or techniques to remove turbidity, metals and harmful chemicals from water.
There is no academic research on the WADI system. However, an overview of research on solar disinfection (SODIS) is available here.
WADI follows the WHO Guidelines for safe drinking water.
Product evaluation: The evaluation of the WADI consisted of laboratory testing of the product’s performance against all three
classes of pathogens. Testing followed requirements of the solar (UV and heat) technology-specific protocol. Following the manufacturer’s use instructions, three units (triplicate replicates) were evaluated for all three classes of pathogens in general and challenge test waters. A solar lamp was used to provide 550 W/m2 of simulated outdoor solar radiation in a laboratory setting. This irradiance corresponds to what would likely be observed between latitude 15° N and 35° N as well as 15° S and 35° S, where the majority of developing countries are located.
Another evaluation report carried out by Agency of Cooperation and Research in Development (ACORD) in Uganda is available.
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