An 18-year-old Australian scientist invented a new way to measure UV exposure for the solar disinfection of drinking water. It was this invention that got Macinley Butson the 2019 Australian Stockholm Junior Water Prize winner at the World Water Week. A sticker using solar disinfection to kill microbes in water.
Xylem sponsors the Australian Stockholm Junior Water Prize. The competition welcomes students between the ages of 15 to 20 who have conducted water-related projects of scientific, social, environmental, or technological importance.
Butson has always been involved and interested in science, but it wasn’t until she learned some shocking statistics about people dying from water that her attention was drawn to it. “I knew about water issues, but I didn’t know the extent of the problem,” said Butson.
The young scientist explained:
I came across two statistics that struck me to the core. These were that 80% of diseases in developing communities are related to poor water quality and that the World Health Organization (WHO) estimates that one in five people who undergo minor or major surgery in a developing community will pass away as a result of infection due to a lack of sterile water.
Upon discovering this information, Butson was determined to tackle the problem. She developed the SASS (sanitation and sterilization) system, which is a solar-powered, portable unit that provides safe, clean, and sterile water for medical purposes.
The water is passed through a chemical filter before it goes through a SODIS (solar disinfection process), which kills bacteria by using the UV in sunlight. Finally, the water can be sterilized in a pressure cooker, which is powered by a solar panel that’s attached to it. “The system can be flat packed, it can be chucked in the back of a car and taken wherever necessary,” Butson added.
Butson notes:
People have said it could be used for disaster relief or in areas where water has been compromised. For me, this project became less about the fact that I invented something and more about the idea that it is possible to develop solutions to these problems.
The amount of time required to perform the SODIS process accurately depends on many factors such as season, location, time of day, altitude, and weather conditions. The WHO’s recommendation for solar disinfection is to put the water in the sun for six hours. However, Butson has a different point of view.
She said:
This is very vague, especially if you’re living in the Himalayas or Africa – those two conditions are very different. Solar sterilization is a process that isn’t dependent on the amount of time but is dependent on the exposure, which between those two places vary significantly.
The SODIS sticker is Butson’s solution to this problem. The sticker can precisely measure whether water has been exposed to an amount of UV significant enough to be safe for drinking or medical use. The SODIS sticker is made up of a partial UV blocking filter and a transparent UV sensitive film, generally used for radiotherapy. According to Butson, the combination allows for both reflected and incident light to be measured.
Butson explained:
Every other detector can only measure directly incident UV radiation because the detectors have an opaque backing, or because the detector is a solid-state detector that cannot measure reflected UV radiation being only unidirectional.
The sticker, which looks like a donut, includes a colored ring attached to a white sticker base. The film sits within the inner circle, which changes its color depending on how much UV exposure it has received.
Butson had to meet a strict criterion when she was developing the SODIS sticker, including:
- Cheap to produce.
- Easily attachable on to or next to a standard PET water bottle.
- Small enough not to block any UV radiation to the bottle.
- Simple to use and to interpret.
- A film that can be seen easily.
- Water and dirt resistant.
The SODIS sticker checks all of these boxes. When Butson produced the sticker at home, having bought the materials at retail price, it cost under $0.01 to make. “I expect that with wholesale and large volume purchases, the cost will be significantly reduced,” she added. The low cost of this invention makes it appropriate for use in developing countries.
Butson said:
My results show the SODIS sticker is an effective way to determine the solar biological disinfection of water and could potentially significantly further improve the sanitation of drinking water for those in need and improve their quality of life.
After Butson tests the SODIS sticker in Australia, her next steps will be to see it used in the field. The young inventor is also working on an improved UV filter to work in unification with the UV sensitive film.
