Young sludge disposal researcher looks to future

Huan Liu is a PhD student at the University of Technology Sydney (UTS). Her cutting-edge research uses a by-product from wastewater treatment for sludge disposal.

Treating wastewater in Australia produces 1.4 million tonnes of sludge, which must be treated and then disposed of. The process is responsible for 50 per cent of the total operating costs of wastewater treatment plants. PhD student Huan Liu has developed a new treatment technology that would reduce the amount of waste by 15-40 per cent and recover energy from the sludge itself.

Liu’s technology would result in an end-product that is a safer biosolid for fertiliser. Her technology relies on a by-product of wastewater treatment. The closed-loop methodology ensures that fewer resources are used in the process.

But who is this woman that has made a ground-breaking difference in wastewater treatment?

Sludge disposal researcher making a difference

Liu is originally from a small city near Xi’an in Shaanxi Province, China. She started her academic career at Northwest University in China. Liu then completed her master’s degree at Shaanxi Normal University.

After finishing her master’s degree, Liu started working as an environmental engineer. Her primary focus was oil sludge and sewerage sludge within the solid waste treatment.

“This experience motivated me to go further within sludge. In my working experience, I realised that there are many gaps in research and applications. I wanted to find new technologies in sludge treatment,” said Liu.

When looking to do her PhD, Liu received two offers from different Australian universities. She wanted to study in a robust environmental engineering institution and felt Australia’s environment would be more conducive to her studies. Liu found her way to the Centre for Technology in Water and Wastewater at the University of Technology Sydney (UTS).

Liu is studying under Professor Qilin Wang, an Australian Research Council Future Fellow. She has found him to be an inspirational leader, with him being appointed as a Professor in Environmental Engineering only seven years after receiving his PhD.

“Professor Wang is my principal investigator. He’s very passionate about his work, supportive and responsible for his students,” said Liu. “I have learned a lot of professional knowledge from him about wastewater and sludge. His career has inspired me, particularly in promoting myself to academics and industry. I’ve seen how he has received funding from different groups, so I want to model myself on him.”

New technology results from luck and collaboration

Liu has developed technology to improve antibiotic-resistant genes and pathogen removal, enhancing anaerobic sludge digestion and boosting the dewaterability of digested sludge.

“I was doing some lab work focusing on the wastewater treatment process. One of the by-products was found to be biocidal for bacteria. I thought this unique by-product could be used in sludge treatment to break down bacteria in sludge. When I tried the idea, it was successful, so the technology came out well,” said Liu.

The process is also much more efficient at removing pathogens. Liu showed a 60 per cent reduction in pathogens and a 20 to 70 per cent reduction in antibiotic-resistant genes compared to traditional procedures. According to the New South Wales Environmental Protection Agency, the residue waste could achieve Grade A biosolids. That would reduce the health risks of using the treated sludge as fertiliser, creating an additional revenue stream for water authorities and local councils.

“Instead of being a contaminant for wastewater treatment plants, the waste by-product becomes a useful part of the process,” she said.

Industry partners key to progress

Partnership and cooperation have been essential to Liu’s research. The water industry has been active in working with researchers across Australia. Liu thanked Water Research Australia Limited, South East Water and the Australia Research Council for supporting her research.

“Not only is the water industry important for providing us with funding, but they also provide us with research materials,” she said. “We need sludge and wastewater samples to do our testing. It would not be possible without the support of our industrial partner. We cannot get these materials, and they can provide the samples regularly.”

Liu also appreciates the industry’s role in explaining what they are looking for in her research. She explained that they have been clear about their immediate needs, which has helped her broaden her mind. It has given her several practical areas to look at in her research.

She praised UTS for its focus on the commercialisation of research outcomes. While Liu’s technology is still in its earliest stage, she is working on developing a patent for it. Ideally, her technology will be pushed to a commercial level in the future.

“UTS has provided me with an outstanding platform for research,” said Liu. “For example, we did an industry project involving removing antibiotic-resistant genes. A project like this can only be completed with the help of an institution like UTS and industry partners. The platforms that UTS provide have been fantastic for researchers such as myself to develop my skills.”

Future of sludge disposal and biochar

In the eyes of Liu, there is enormous potential in developing technology for the water industry, particularly for wastewater treatment plants.

“I noted an Australian-first project that saw wastewater turned to energy, which will support the country’s energy demands,” she said. “I’m also really excited by the possibility that the technology I have developed could bolster the energy recovered from sludge, further supporting the energy grid. That’s a tangible benefit for the public.”

Liu spoke about the potential of biochar in Australia. She believes her focus on biochar provides more opportunities for Australia.

“I have only focused on the biochar produced by sewage sludge. The technology is not widely used in Australia, but in Japan, they rely on pyrolysis to produce biochar,” said Liu. “This is the way they treat the sewage sludge.”

Pyrolysis is a technique where a material is heated above its decomposition temperature. That temperature will see chemical bonds broken down in the molecules. These fragments can become smaller molecules or combine to produce residues of a larger molecular mass. Some small trials and demonstration plants exist in Australia, particularly in southwest Western Australia, Melbourne, and central Queensland.

“The biochar produced because of pyrolysis needs to be dried first, so the solids content needs to be as high as 90 per cent. This is different from hydrochar, which operates from a slurry,” said Liu. “Having said that, there is undoubtedly potential for hydrochar and biochar -. But the hydrochar and biochar could hardly work together. They use different raw materials and production processes while generating different char properties.”

Where Liu can go in the future

Beyond the commercialisation of her technique, Liu has two potential avenues for expanding her research.

“Firstly, I want to focus on the mechanism, performance and application of my technology,” said Liu. “I want to understand how it works from a biological and chemical point of view. Conducting more experiments to investigate the mechanisms will almost certainly provide a broader pathway towards commercialisation.”

Her second area of focus is to expand her research into the water treatment process. A new idea has been developed in her team to reduce sludge production in wastewater treatment instead of treating sludge after the fact. The preliminary results of her research in this area are positive, so Liu wants to conduct further experiments in this field.

“I believe there is the potential for more energy and cost savings by reducing sludge production in wastewater treatment,” said Liu. “We have two ways to reduce sludge production. One way is to produce light sludge, reducing the original volume of sludge. The other way is to improve the technology behind sludge disposal and reduction.”

Liu’s original research in Australia focused on reducing sludge after it has been through a wastewater treatment plant. She now wants to focus on reducing the amount of sludge that enters a wastewater treatment plant. In her eyes, it would reduce the energy requirements for the wastewater treatment plants, thereby saving them money.

Liu’s goal is to become an excellent researcher and engineer in the future who can advance the science and practice of urban water management.

Liu is coy about her future in the field.

“I have some new ideas, but it is too early to say what they are.”

This story originally appeared on Inside Water.