It was once believed that the concrete used to build our cities’ sewer pipes would easily last a hundred years or longer. A ‘build and forget’ service, with maintenance only required for what enters its tunnels, and not for the structure itself.
However, in the 1950s researchers discovered that bacteria producing the odorous chemical compound, i.e. hydrogen sulphide, fed another type of bacteria on the concrete surface. The bacteria would oxidize the H2S to sulphuric acid. Sulphuric acid is highly reactive and destructive to concrete, in turn reducing that 100-year life expectancy of concrete sewers to less than 10 years in some circumstances.
The cost of sewer corrosion is massive for our societies, at approximately $10 billion per year for taxpayers and governments in the United States. In Australia, the cost paid via our taxes and water service fees equate to approximately $1 billion per year. Microbial corrosion of concrete is a huge problem worldwide.
Our own efforts to improve another of our world problems – water scarcity - is actually making the situation worse. Our reduced water usage, and subsequent wastewater processes have changed over time. Water saving toilets and more sustainable domestic water practices have inevitably decreased the amount of water rushing through the pipes. However, the amount of waste going into sewers is even increasing with a rising population. Combine this factor with rising temperatures, the bacteria are thriving with higher concentrations of waste, thus leading to higher concrete corrosion in sewers.
Microbial corrosion of concrete is a field Dr Guangming Jiang from UOW's School of Civil, Mining & Environmental Engineering, has been actively working in. He also holds broad research interests in microbial corrosion, environmental health, wastewater processes and treatment.
“I’ve worked on this problem since my time as a PhD student. At the time our work focused on ‘wastewater solutions’. We were testing different chemical dosing strategies in wastewater, to try to remove the H2S and reduce the production of H2S, which in turn controls the concrete corrosion in sewers. Chemical dosing needs to be sustained to be effective. Later on, I moved on to the concrete solution: new technologies to make the concrete more resistant to H2S induced corrosion.”
Dr Jiang has worked in teams funded by various grants including Australian Research Council linkage projects, partnering with water industry and major water utilities in Australia and worldwide to develop solutions.
“We worked through a recent ARC Linkage project on a way to develop a corrosion-resistant concrete by adding a particular chemical admixture to the cement material. The mixture works by inhibiting the bacterial growth on the concrete surface.”
“We have also worked towards biological solutions in the development of corrosion-resistant concrete. We cultivate and harvest bacteria from the wastewater, then we introduce these bacteria to the concrete. The so-called bio-concrete, developed through my ARC DECRA project, was shown to have excellent resistance to the corrosion.”
It is through his research fellowships, cross-university collaborations and broad industry connections that have propelled Dr Jiang to the forefront of his field. His previous research has led to fully commercialised technologies and patents across the globe. He provides consulting and testing services to major wastewater infrastructure projects globally, such as the Singapore Deep Tunnel Sewerage System Phase II and the Auckland interception sewer in New Zealand.
“Dr Jiang´s institute was selected as one of the global testing institutes for performing 1 year corrosion test for the Singapore Deep Tunnel Sewerage System Phase II. We appreciated his outstanding expertise in biogenic corrosion mechanisms and testing of concrete during our collaboration. His results enabled us to understand the deterioration and long-term durability of concrete. He and his team proved that our Calcium Aluminate Cement based solution is especially suited for this type of environments.” Said Dr. Markus Schmid, who is the Group Leader Applied Technology at CALUCEM GmbH, Germany.
Dr Jiang is actively seeking to establish collaborations with concrete companies and water utilities to conduct research on testing and developing promising and innovative concrete technologies for sewers. Dr Jiang is working towards keeping our wastewater running efficiently, repairing legacy assets and helping build better infrastructures for the future. On top of all of this, he contributes to the health and wellbeing of our communities by doing research about the wastewater monitoring of COVID-19 and drug usage.
Wastewater-based epidemiology (WBE)
Wastewater-based epidemiology (WBE) is an approach in which the concentration of chemical or biological biomarkers in domestic wastewater is analysed with advanced chemical or biological methods to back calculate the community consumption or exposure to chemicals and the prevalence of infectious diseases. Research has been done on chemicals like illicit or pharmaceutical drugs and compounds related to lifestyles - including nicotine and alcohol. Biological biomarkers like pathogenic viruses in wastewater were detected to determine the infected number of people.
“Systematic sampling and analysis of wastewater samples are increasingly adopted for estimating drug consumption in communities. An understanding of the in-sewer transportation and transformation of illicit drug biomarkers is critical for reducing the uncertainty of this evidence-based estimation method,” says Dr Jiang.
WBE has been brought into the general public lime light, with media often referring to it when detecting the prevalence of coronavirus disease 2019 (COVID-19) in the community. The surveillance of COVID-19 spread, and resurgence are crucial for governments to reduce adverse effects and implement timely control measures. WBE has become essential in the monitoring process of the COVID-19 pandemic.
Through his research experience, previous academic collaborations and industry connections, Dr Jiang actively work on some COVID-related projects funded by Australian Research Council, the Australian Academy of Science and the Department of Industry, Science, Energy and Resources.
“Initially, we collected wastewater samples from a cruise ship and Qantas airplanes, with mostly international travellers. Our first paper examined how to detect the virus from these travellers before they disembarked. We then worked on the WBE methodology itself, how to improve the accuracy, or reduce the uncertainty. SARS-CoV-2 is a new pathogen and we were unsure how the virus would decay in the wastewater environment.”
“Our study provided essential information about the feasibility and accuracy of data-driven estimation of COVID-19. Without the international collaboration, and industry engagement, findings would be hard to achieve in such small timelines.”
Going forward Dr Jiang hopes to broaden collaborations involving artificial intelligence like machine learning to improve the prediction capability of WBE for COVID-19 monitoring through wastewater analysis, and overall long-term solutions to real-world problems. He leads the Asia-Pacific Network for Wastewater Monitoring of COVID-19 (www.watmoc.com), with members from USA, Canada, Japan, Spain, and India.
“There are vast amounts of space for IoT (Internet of things) or big data technologies within this space. Taking WBE for example, we can have IoT sensors or portable devices put in the sewer system, then we can monitor real-time data of various pathogens or chemical compounds. My research vision is to achieve sustainable, resilient, and smart urban wastewater infrastructure. Sewers are not only smelly pipes transporting wastewater but will become an information network for public health in the modern society. I hope my research about sewer corrosion will make concrete sewers resilient to the ever-increasing challenge of global warming and population growth. Similarly, my research on wastewater-based epidemiology will develop smart solutions to extract valuable information from sewers.”