A diagram illustrating how the UW device works (Image: University of Washington)
The worldwide shortage of clean drinking water is a serious problem, although in many cases there’s a relatively simple solution – just leave the tainted water outside in clear plastic bottles, and let the sun’s heat and ultraviolet rays purify it. This approach is known as SODIS (SOlar DISinfection of water in plastic bottles), and it removes 99.9 percent of bacteria and viruses – results similar to those obtained by chlorine. Unfortunately, however, there’s been no reliable way of knowing when the water has reached a safe level of purity. Now, four engineering students from the University of Washington have created a simple, inexpensive device that does just that... and they won US$40,000 in the process.