We are designing a small but powerful device to test water quality at the final source of a communal drinking supply. The inventive use of low-cost UV sources and sensors should allow us to create a cheap and easy-to-operate piece of technology usable by a local population and NGOs for safety purposes and research collection.

Background
We focussed our design on Lagos, one of the largest and most rapidly urbanizing cities in the world. Its high density living and high income disparity provide particular challenges to their water infrastructure.

Audience
Community organisations such as schools and health centers; and institutions like WaterAid and the UN.

User Scenario
A teacher in a local school uses the Canary to test the water from the local well before their students drink it. If the Canary shows that the water is unsafe to drink, the teacher can use chlorine tablets or boil the water to make it safe to drink. The teacher would use this process to also educate students on water safety issues.

Implementation
Using the knowledge that UV light is absorbed by the DNA of pathogens at 270nm, we created a hand-held device that passes UV light from a inexpensive Xenon flash through a filter, through a test tube of the sampled water, to a UV sensor on the other side. The sensor gives us a reading which we compare to a control sample (water we know to be clean) to give a simple 'Safe' or 'Unsafe' output.

Conclusion
Keeping cost of parts down to a realistic level for the user groups we have in mind was our biggest challenge.