Low-cost water sensor wins regional science fair

Three sixteen-year-old pupils won the regional science fair on Wednesday with a water-quality sensor built from parts costing less than a school lunch. The judges chose the project from 86 entries submitted by 31 schools.

The device measures how cloudy a water sample is and how well it conducts electricity, two readings commonly used as a first check on river health. It sends the results to a phone every ten minutes and runs for about three weeks on two small batteries.

How it was tested

The team placed six sensors along the river over the summer holidays and compared their readings with samples analysed in the school laboratory. The two sets of results agreed to within eight per cent, which the judges described as a careful piece of validation for a school project.

The pupils were open about the limits. The sensor does not detect specific pollutants, and its readings drift when the probe is covered by algae, so it has to be cleaned weekly.

What happens next

The prize is a place at the national final in the spring and a grant of 2,000 for the school's science department. The team says it will use the months before the final to add a temperature probe and to test a casing that keeps the sensor clean for longer.

Second prize went to a study of bee visits to different balcony plants, and third to a method for sorting plastic waste by the sound it makes when dropped.