Ear to the ground

An acoustic sensor system to monitor the UK’s ageing sewer network could help utility operators boost efficiency and cut costs by providing accurate, real-time information about the state of the nation’s vast infrastructure, its developers have claimed.

Two of the country’s biggest water companies are backing development of The SewerBattsystem by engineers at the University of Bradford.

SewerBatt uses sonic wave technology to provide a detailed picture of any blockages or change in flow-rate inside the UK’s 300,000 km of sewerage pipes, and could have wider applications in areas such as oil transportation.

According to Dr. Kirill Horoshenkov, lead researcher at Bradford’s school of engineering, design and technology, the system promises to save water companies millions in surveillance costs.

‘In total, water companies own around £1bn of underground assets but have very little knowledge of the state of them,’ claimed Horoshenkov. ‘Even the best water companies probably have detailed knowledge of only about half a per cent of their own network.’

New legislation due to be introduced in 2010 — the fifth part of OFWAT’s five-yearly Asset Management Plan — will force water companies to provide accounts on the condition of their water and sewerage network.

At present, the only means utilities have of monitoring their underground assets are both time-consuming and expensive. Most use CCTV cameras installed in the pipes at key junctions, but pipe analysis is undertaken by operators watching a screen above ground. This system is fundamentally flawed, according to Horoshenkov.

‘Current methods are both time consuming and completely subjective,’ he claimed. ‘Studying a CCTV image to look for blockages and damage is very open to interpretation, and depends on the skill or experience of the operator. This makes it very inconsistent and labour-intensive.’

Because of the prohibitive costs of monitoring the entire network in this way, two of the UK’s biggest water companies are contributing to the new system’s research costs, alongside EPSRC funding. Together, Severn Trent Water and Yorkshire Water are contributing around one-fifth of the £260,000 costs.

The SewerBatt system uses sonic waves, which propagate much more effectively than radar in sewers. The technology should be able to spot blockages or other problems with the network far earlier than would be possible using human operators.

The sensors send a coded sequence via sound waves, and then listen for the echo-response reflected from the tunnel walls. Any changes in the pipe, or the amount of water inside it, result in different responses being received by the sensor.

Collected data is then sent to a hand-held device such as a PDA, which either processes the signal itself or will store the data from the sensor digitally and send it to a central processing unit. A software system analyses the acoustic responses and will be able to detect even the slightest changes in the pipe.

‘Even a blockage of less than one per cent of the pipe’s diameter will give back a different reading,’ claimed Horoshenkov.

The system could be used in a number of ways. A sensor can be fixed to a position on the walls of the sewer at regular intervals — ideally one per section of pipe. An operator would also be able to lower a SewerBatt sensor through a manhole to obtain a quick ad-hoc readout of the state of the pipe below.

If excess traffic loads above ground damage the pipe, Sewer- Batt will be able to detect if the pipe cross-section changes slightly. Also, in the older brick sections of the network, the system will detect if bricks go missing which could potentially block the flow further downstream. The technology is waiting for a patent grant, and Horoshenkov has plans to link the sensors together via wireless networking technology in the future.