Instant readings on river pollution

A cheap, hand-held device that gives almost instant readings for pollution levels in rivers has been designed by scientists at the University of the West of England.

Researchers in the university's advanced sensors research group built the small sensor, which can detect tiny quantities of ammonia in water. It can be used at the riverbank to generate pollution readings almost immediately.

David Cowell, director of the university's centre for applied research in sciences, said that the present method of detecting ammonia in water requires samples to go to a lab, where processing costs about Pounds 7.50 a test and can take some time. The new single-use detectors, however, should cost about Pounds 1 to Pounds 1.50 to produce.

"The idea is to do the test at the bankside very cheaply," Dr Cowell said. He said that ammonia is highly toxic to fish and tends to leak from slurry tanks or malfunctioning sewage treatment works. Quick detection of even low levels of leakage is important.

"The new sensor is so sensitive that it can detect ammonia in a concentration of as little as 20 parts per billion - the equivalent of detecting a pint of beer that has been added to an Olympic-size swimming pool - but it is also portable," Dr Cowell said.

The sensor works by using an enzyme, glutamate dehydrogenase, which is activated by ammonia. The enzyme is put on a carbon bed that has been screen-printed on a piece of plastic. Ammonia's presence activates the enzyme, allowing electrons to flow that can be picked up with the carbon and recorded by the sensor.

The prototype is being developed into a marketable product.