Electric bacteria could save millions

When not working with sludge from Melbourne's sewers, La Trobe University scientist Elizabeth Mathews is busy thinking about it.

Her doctoral research study is one that few would envy – trying to change the respiratory or 'breathing' chemistry of bacteria in our waste stream.

Why? 'A healthy society is built on good sanitation,' she says. 'And many of our sewers are ageing and breaking down as a result of pipe corrosion, a by-product of bacterial respiration.

'Replacing corroded sewer pipes costs staggering amounts of money,' she said.

Ms Mathews is a member of La Trobe's Environmental Microbiology Laboratory, which studies a wide range of bacteria that 'breathe and eat electricity' to power their biological processes.

Our lungs and respiratory system works by taking in air, removing oxygen and exhaling carbon dioxide. However, anaerobic bacteria in sewers thrive on sulphur, which they expel as hydrogen sulphide – more commonly known as rotten egg gas.

'The gas forms sulphuric acid,' said Ms Mathews.  'And the acid attacks concrete, which causes corrosion, weakens sewer pipes and eventually leads to their collapse.'

Disrupting two of the most common bacteria

So her aim is to disrupt the respiratory cycle of two of the most common types of sewer bacteria, replacing their sulphur diet with one of electrodes.

'The bacteria can then use the electrodes to complete their respiratory reactions – but without producing hydrogen sulphide and sulphuric acid in the process.'

Ms Mathews said these electrodes were economical, long lasting, and could be added to the existing sewer system.

Her project, being carried out with the help of Western Water, is studying a wide range of bacteria in residential and industrial sewer streams. Some of these sewers show signs of corrosion and some don't.

'By analysing them we will get data to help design the most effective electrodes to convert the bacteria's diet from sulphur to the electrodes,' she said.

Less corrosion – and no need for chemicals

Western Water's Customer and Community Relations Manager, Graham Holt, said without the hydrogen sulphide being converted into sulphuric acid in sewers there would be much less corrosion and no need for expensive chemicals.

He said the project has great potential for use across the whole Victorian water industry.

'If we come up with a workable solution for this problem, it could save Western Water more than $100,000 a year – and millions of dollars a year across Victoria,' he said.

The Electric Bacteria program in La Trobe's Environmental Microbiology Laboratory is led by Dr Ashley Franks.

'The aim,' said Dr Franks, 'is to manipulate these processes to help clean up waste and pollution, produce energy more efficiently – and maybe even as an alternative to petroleum.'

Photo: Elizabeth Mathews, right, and Dr Franks sampling a section of sewer at Melton in Melbourne's west, with Western Water's Manager of Field Services and Network Operations, Dean Barnett, left. (Photo: Western Water)

Media Contact: Ernest Raetz, 0412 261 919

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