Something rotten in the state of sewer pipes

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Water utilities are getting smarter in how the monitor and manage their underground pipe networks. We recently reported on how SA Water is using acoustic sensors to detect pressure surges and leaks in its Adelaide CBD water mains. Now, Melbourne Water is trialling the use of new technologies to help monitor the condition of more than 400kms of sewerage mains across Melbourne.

One of the biggest problems with concrete sewers is corrosion caused by hydrogen sulphide – the ‘rotten egg’ gas produced by decaying vegetable matter.

And this problem is getting worse, thanks to efforts to reduce water consumption. A 2013 article on The Conversation by researchers at Victoria University reported: “By reducing water and replacing potable water with rainwater, treated grey water and wastewater, we are simply creating more concentrated wastewater. It’s this concentrated wastewater that leads to a higher percentage of odour-producing gases and a greater rate of pipe corrosion.”

The authors modelled hydrogen sulphide production under various water conservation strategies and concluded: “The average lifespan of sewer pipes under [the modelled] conditions would be reduced from 147 years to just 70 years, causing major issues for water authorities charged with maintaining and replacing the network.”

Melbourne Water has for years been using remotely controlled CCTV cameras to monitor the internal condition of its sewer pipes, but these are unable to detect reductions in wall thickness caused by the action of hydrogen sulphide.

To overcome this problem Melbourne Water has developed a remotely controlled device that uses a combination of radar, cameras, sensors and laser technologies to measure concrete pipe wall thickness and surrounding environmental conditions.

According to Melbourne Water’s general manager, asset management services Gerald FitzGibbon, this technology can relay important information about pipe thickness, the location of steel reinforcements, internal pipe diameter, pH, temperature and humidity back to asset management staff.

“The device will allow our asset engineers to more accurately predict the remaining service life of our assets and design rehabilitation works to extend it,” he said.

“This cutting edge technology will help us go from reactively fixing problems once they appear to being able to predict potential failures and schedule maintenance work before they occur. This is expected to help us to minimise disruption to the community and provide a better level of service at a reduced cost by fixing potential problems before they impact on customers.”

Melbourne Water expects to deploy its first device for testing in August and has issued a call for expressions of interest to find partners for the project.

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