A novel gas sensor developed at Manchester University has emerged as the instrument of choice for the detection of contaminated water before it wreaks havoc in treatment plants.

Recently rated by the UK’s Water Research Council (WRC) as the best device for the monitoring of trace hydrocarbons, it out-performed optical or fluorescence-based sensors for sensitivity and robustness.

Following WRC recommendations, the instrument is being tested by Thames Water, Yorkshire Water and Southwest Water. It is being commercialised by Multisensor Systems Ltd which GOSPEL board member Prof Krishna Persaud spun out of Manchester University in 2007.

Essentially a gas detector based on metal oxide sensors, but with intelligence built into it, the multisensor system is designed to look for abnormalities and recognise unusual events. The device sits above an inlet stream and can detect hydrocarbons or other contaminants with extremely high sensitivity. By tuning the sensor to recognise particular contaminants, it can detect diesel or petrol in water at fifty parts per billion or 50 micrograms in a litre.

The device has also been tested for detection of unusual or abnormal loads entering sewerage plants. Replacement of a filter bed can cost up to 16m, so the water industry is very interested in early detection of contamination. “Illegal discharges such as a farmer dumping chicken blood or a brewery flooding a sewer with beer is the equivalent of fly-tipping in the water world,” Persaud says. “These events cause tremendous problems to the operators of sewerage plants, which are typically unmanned and remotely located.” Detection of contaminated water before it arrives in the plant gives operators time to divert the flow to a holding area for slow release at a rate which bacteria can cope with.

Most sensors fail rapidly when immersed in toxic and corrosive sewage, which gives gas sensors a competitive edge. The device being developed by Manchester University and Multisensor Systems is configured to provide data via a telemetry system, which allows remote monitoring. It is designed for long-term unattended use with mains power.