Hydrogen sulphide wreaks havoc in sewer assets, leading to widespread disruptions and costly corrosion damage, but a team of Queensland researchers may have a new solution.
In Australia, sewer systems have an estimated asset value of $100 billion, representing 70 per cent of the total wastewater services infrastructure.
Hydrogen sulphide-induced corrosion can reduce the service life of sewerage infrastructure assets to just 20 per cent of their designed lifespan. Meanwhile, sewer odour nuisance accounts for over 90 per cent of community complaints.
Dr Jiuling Li, research fellow at The University of Queensland’s (UQ) Australian Centre for Water and Environmental Biotechnology (ACWEB), set out with his team to devise a system capable of better maintaining sulphide levels, thereby reducing odour complaints and costly corrosion issues.
This led to the development of a new real-time control and chemical dosing technology, which has now been recognised worldwide and was awarded a Silver Project Innovation Award from the International Water Association (IWA), for successfully and innovatively tackling odour and corrosion in sewers.
Where it all began
Equipped with a bachelor’s degree in Automation from China’s Harbin Institute of Technology, Dr Li first dipped his toes into the world of water monitoring when he completed a PhD at UQ in 2021.
“My research mainly centres around digital water systems,” Dr Li said.
“More specifically, it includes developing tools like model predictive control, real-time control systems, IoT sensor networks and high-performance computing. These innovations help optimise the operational maintenance of sewer systems and wastewater treatment plants, as well as promoting more sustainable water management practices.”
Dr Li explained that hydrogen sulphide is produced by the sulphate reducing bacteria found in sewers.
“This gas is volatile and can escape from the wastewater network into the sewer air, creating unpleasant odours. Additionally, when the sulphide in the sewer air interacts with the sewer waters, it can convert to sulphuric acid, leading to the corrosion of the sewer infrastructure,” he said.
“Sulphide is a major cause of sewer corrosion, resulting in the premature degradation of sewer assets. Replacing or repairing damage to sewers costs billions of dollars per year.
“Moreover, the frequent inspections and maintenance that is required regularly exposes workers to hazardous environments and increases the water bills of residents.”
According to Dr Li, the odour of sulphide gas can also cause significant disruption to people living and working in the area and can even result in health risks due to its toxicity.
Innovative dosing control
To mitigate these challenges, water utilities often use methods like constant, flow-paced and profile dosing for controlling hydrogen sulphide levels.
“But these approaches rely on fixed guidelines and they don’t account for fluctuations in the sewer systems, leading to ineffective control and resulting large amounts of chemicals wasted,” Dr Li said.
According to Dr Li, with the predictive modelling sulphate control technology, network managers can use historical data from their sewer operations to predict the changes in sewerage flow and sulphide levels across the entire sewer network ahead of time.
“The technology employs an efficient optimisation algorithm to determine the ideal amount of chemicals to dose in real time. This ensures that the right amount of chemicals can be delivered to the sulphide hotspots whenever the pump runs, providing continuous control with minimum chemical costs.
“The technology is a result of a long‑standing partnership between UQ and our industry partners, supported by more than 20 years of collaboration with more than 25 projects funded by the Australian Research Council and the government.
“In 2013 our team developed the first generation of this control methodology for chemicals, which was limited. With advances in digital technology, we developed the second-generation system which digitalised the whole chemical dosing control process.
“This work was supported by the Australian Research Council and our industry partners, including Urban Utilities Brisbane, Gold Coast City Council and SA Water.”
Internationally recognised
The IWA holds the Project Innovation Awards biennially at its World Water Congress & Exhibition, to recognise and promote excellence and innovation in water management, research and technology.
At the 2024 congress, Dr Li and his team were celebrated for their efforts and awarded silver in the ‘Smart Systems and the Digital Water Economy’ category.
“What sets us apart is our commitment to knowledge transfer. Every aspect of our work is designed with the ultimate goal of real-world application, all held to a high scientific standard.
“Our multidisciplinary approach has brought together academic researchers and sewer operators to develop an innovative digital solution for sewer maintenance,” Dr Li said.
“The term ‘digital water’ is an emerging concept, and most efforts remain at the research or lab stage. We are the first team globally to have successful implemented an advanced control theory in a real, large-scale sewer network for chemical dosing.
“By focusing on practicality and user needs from the start, we have been able to transform innovative ideas into effective and real-world applications.”
The control system is currently being tested in two sewer networks in Queensland – one on the Gold Coast and one in Brisbane’s western suburbs.
“By improving dosing effectiveness and efficiency, we estimate the technology can reduce chemical use by around 40 per cent in most dry weather scenarios,” Dr Li said.
Dr Li said that the technology presented significant challenges due to its multidisciplinary nature.
“Unlike most control projects that focus solely on sewerage flow, we have to account for the complex chemical and biological processes occurring within the whole sewer catchment.
“The real-time evaluation requires high-resolution predictions of dynamic changes across a large-scale network at the millisecond level. This results in not only a demanding task in water engineering, but also a complex problem in mathematics and automation.
“With the support from our partners, we overcame these challenges by assembling a diverse team of engineers, microbiologists, mathematical modelers, computer scientists and sewer operators and I think our team’s perseverance has been key to our success.”
Improving environment and community
Dr Li said that this technology will greatly reduce odour complaints in residential areas and provide effective tools for ongoing sewer maintenance.
Image: Gena Melendrez/shutterstock.com
“It helps ensure the integrity of the sewer system, preventing overflows and even flooding, which reduces the risk of pollution and the spread of pestilence.
“Ultimately it creates a safer and more pleasant environment for residents.”
Dr Li said that the technology is expected to extend the service life of sewer infrastructure and reduce chemical consumption.
“It will also decrease the need for new construction, and the less sewer infrastructure being replaced means less solid waste production. It also lowers the energy cost associated with the pump and reduces the carbon footprint of maintenance activities. All of this contributes to net zero goals.
“Although the hydrogen sulphide itself is not greenhouse gas, the sewer system generates significant amounts of methane, a potent contributor to global warming. Chemical dosing is also the key approach for methane mitigation, which is another major focus of our ongoing research.”
Dr Li said that it’s important for utility managers to recognise that the hydraulic retention time and the sulphide levels across the sewer network can vary significantly from hour to hour, and day to day.
“Additionally, the optimal amount of chemical dosing can be quite different between pump cycles,” he said.
According to Dr Li, current sensor technology is still susceptible to issues like humidity and sulphide exposure, so implementing a smart monitoring system and backup plans for anomalies or sensor failures is crucial for optimal sewer operation and maintenance.
The next phase
While the technology has already shown great results, Dr Li said that this is just the beginning.
“We still have some theoretical designs that haven’t yet been implemented in practice, and we believe this could further enhance the control performance, so we are actively seeking opportunities to test them,” he said.
“Meanwhile, we plan to automate technologies designed to ensure that operators and engineers without specific expertise can easily use them. Our goal is to commercialise the technology, making it accessible to a broad range of users.”
Dr Li said that the technology also holds great potential for broader applications across not only the sewer system, but across the water supply and wastewater sectors, supporting a more integrated approach to water management.
“This will be essential for developing sustainable cities and ensuring the long-term effectiveness of water services,” he said.
“Digital management of sewer networks offers benefits far beyond the sewer system itself. It can improve the operation of clean water systems and wastewater treatment plants as well.
“All of these systems are managed independently. The future of digital management should focus on creating integrated solutions that consider broader, collaborative management.
“My hope is that digital water technologies, whether lead by the industry or a research institution, will result in practical, wide-ranging and long-lasting technologies rather than individual solutions, so that these technologies can contribute to environmental protection and public health across the water industry.”
