Save our sewers

This data was used to create a sophisticated mathematical model that predicts localised variations in sulfide, methane and other parameters such as pH within sewers.

“Thanks to SeweX we have saved $30 million in capital costs,” says Bill Capati, Manager, Sustainability Services, City of Gold Coast, who originally approached Professor Yuan seeking a remedy for the Gold Coast's sewer network problems.

SeweX has been highly awarded, receiving the Australian Engineering Excellence Award (Innovation Research and Development Category, Queensland Division) and the International Water Association Project Innovation Award (Applied Research Category, East Asia and Pacific).

As a result of the SeweX research in close collaboration with industry partners, in 2008 the AWMC received the second highest Linkage grant ever awarded from the Australian Research Council to establish the Sewer Corrosion and Odour Research (SCORe) project, the world’s largest ever sewer research project.

Receiving $21 million in funding from the Australian government and major Australian water utilities, the project involved five research and 11 industry partners, who collectively provide wastewater services to approximately 60 per cent of the country's population.

One of the technologies to emerge from this project was an affordable, environmentally friendly method of decreasing hydrogen sulfide production in sewers.

"Existing management techniques focus on using continual dosing of chemicals to remove the sulfide after its formation, which not only costs almost as much as asset loss, but also causes problems in the sewage treatment and reclamation process," says Professor Yuan.

The team developed an affordable technology that produces environmentally friendly, free nitrous acid (FNA) from the sewage itself.

“The FNA targets and kills the organisms that create the odour and corrosion, and is then removed itself by the microbial community living within the sewage pipes.”

Field trials in Australia showed that it could achieve a 75 per cent reduction in operating costs compared to the existing continual dosing techniques.

The FNA technology was developed into the commercial venture Cloevis Pty Ltd, led by UQ’s commercialisation company UniQuest. Cloevis has since partnered with USP Technologies to take the technology to the US market where, after undergoing field trials, is now in full commercial mode.

A third business to spin out of AWMC’s research is Lodomat, which uses FNA to reduce costs in wastewater treatment plants.

One of the main costs of treatment plants is the disposal of sludge, a by-product of the treatment process. Lodomat technology uses FNA to reduce the amount of sludge by up to 10 per cent. It is easy to install and retrofit, and can pay for itself in just two years. A parallel benefit is that Lodomat also increases biogas production from anaerobic digestion of sludge by 20 to 30 per cent.

Taking a holistic approach to the problem, the researchers have also investigated whether it is possible to reduce the amount of sulfates in wastewater in the first place.

Professor Yuan’s team performed a two-year sampling campaign across South-East Queensland from 2009–2010, as well as conducting an extensive water industry survey across Australia, and producing comprehensive computer modelling of sulfate sources.

They found that aluminium sulfate added as a coagulant during the production of drinking water was a large contributor to the amount of sulfate in wastewater, and was indirectly the largest source of hydrogen sulfide in sewers.

A report published in Science in May 2015 recommended that simply by switching to sulfate-free coagulants, at little or no extra cost, water utilities could save large amounts of money in sewer corrosion.

In 2015, Professor Yuan’s research was recognised by the Australian Academy of Technological Sciences and Engineering (ATSE), which awarded him a Clunies Ross Award, one of Australia’s top technological sciences awards. He was also named one of Engineer Australia’s Top 100 Most Influential Engineers for 2015.

Recent work on an experimental wastewater system in the AWMC laboratory has shown that a sulfate-free drinking water coagulant, iron chloride, yields multiple environmental and economic benefits when present throughout the wastewater system.

When iron chloride is added to sewers, it removes odorous and corrosive hydrogen sulfide. At the wastewater treatment plant, iron chloride traps phosphorous, helping to prevent harmful algal blooms when treated wastewater is discharged to waterways.

Removing hydrogen sulfide also improves the quality of biogas (methane) produced by anaerobic digestion at the wastewater treatment plant.

This work again demonstrates the benefits of an integrated approach to managing the entire urban water cycle, from drinking water to sewers and wastewater treatment plants.

Professor Yuan is quick to emphasise that none of this work would have been achieved without the commitment from AWMC’s industry partners, who not only provided funding, but also provided avenues for implementing the research. Their advice and insight based on practical experience has been essential in developing innovative solutions to on-the-ground problems.

“We have committed partners who are looking for innovation,” says Professor Yuan.

In turn, water industry figures are appreciative of how applicable the research is to their needs.

According to Mr Capati, the most valuable feature of Professor Yuan’s research work is how directly relevant the findings and solutions are for water industry practitioners, which has led to rapid industry uptake and substantial monetary benefits.

But it's been a group effort.

“The combination of world-class industry and academic engineers, microbiologists, materials scientists, analytical chemists and mathematical modellers have worked together to develop sustainable solutions to support the cost-effective management of complex sewer corrosion and odour problems,” says Professor Yuan.

“The outcomes of their research will have an enduring impact on the global water industry.”