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Growing global concern about microplastics has spurred a range of research and studies into the different methods that can be adopted to reduce their widespread presence. Recent studies undertaken by South East Water can help water utilities gain invaluable first experiences in sampling and characterising this contaminant.

Concurrent with the increase in production and usage of plastic materials worldwide has been the prevalence of microplastics (MPs); minuscule bits of plastic debris caused by the disposal and subsequent disintegration of consumer products and industrial waste. These MPs can pose a danger to the environment and public health, and have been found in the air, tap and bottled water, sea salt and even in fish caught for human consumption.

The composition of microplastics can create significant health risks, as it can accumulate in the food chain and impact human food. As well as this, other toxic substances and undesirable chemicals can attach to the miniscule particles, and human ingestion can lead to increased exposure to these chemicals and result in harmful health problems.

Sewage is a point source of MPs in the environment, with water recycling plants (WRPs) serving as a pathway for this contaminant to enter the environment. Despite this, existing WRPs across Australia are not specifically designed to manage MPs pollution. The effective management of the MPs risks requires a detailed understanding of the fate and transport of MPs in existing sewage treatment systems.

In addition to this, Australian water utilities generally have limited or no experience in sampling and analysing MPs. There has also been a lack of knowledge about the efficiency of lagoon-based WRPs in removing MPs, a significant gap considering 60 per cent of more than 1,200 WRPs across Australia using ponds/lagoons as the primary treatment step, and 77 per cent using ponds as one of the treatment steps.

In an attempt to better understand – and even potentially mitigate in the future – the prevalence of microplastics in Australian water utilities, South East Water partnered with the RMIT University team led by Associate Professor Linhua Fan to carry out the first long-term MPs study at WRPs in Australia.

Conducted over two years, the study covered the fate and transport of MPs in three of the company’s WRPs, examining different treatment scenarios used by the Australian water industry.

The study

In carrying out this study, South East Water strove to cover all the different treatment scenarios used in Australia’s water industry, selecting three of the most representative WRPs at South East Water that include the most traditional activated sludge treatment process, the most advanced membrane treatment process, and the simplest lagoon-based process. The study covered industry catchment and residential catchment, as well as large-scale treatment plants and small-scale treatment plants.

When it came to conducting research on these microplastics in WRPs, South East Water’s Strategic Research Manager, Dr Li Gao, said there were a lot of challenges. “At the beginning, we didn’t even know how to sample, or how to characterise and analyse microplastics, as no standards were available. This study was the first time a water utility had tried to do this. We needed to learn how to take samples of microplastics from sewage, how to analyse them, and how to characterise them.

“This characterisation wasn’t easy. Sometimes, it can be hard to differentiate microplastics from other materials present in the wastewater samples. You have to use advanced analytic methods to actually differentiate them.” Dr Gao said the study allowed water utilities to gain industry-first experiences in sampling and characterising MPs.

The study identified that the different treatment systems under the study can all achieve promising removal of MPs (more than 97 per cent). Furthermore, a seasonal variation of MPs concentration was also found, which was determined to likely relate to stormwater events in the catchment.

“The results highlighted the potential of low-cost/lowenergy lagoon-based WRPs for microplastics control,” Dr Gao said. “Our findings help to address key knowledge gaps while also helping water utilities successfully manage microplastics in WRPs, mitigate microplastic pollution risks in the environment, and address community concerns.”

Moving towards a circular economy

As well as providing industry insight and knowledge this research is making progress towards helping South East Water move towards a circular economy-based business model. “Recycled water is a very, very important component for the circular economy.

Water is a precious resource, and we need to make use of as many alternative water sources as possible to ensure we protect our drinking water so it can be used where it’s needed most.

“To enable recycled water use, we have to make sure it complies with all the guidelines, and make sure it doesn’t pose any environmental or public health risks.” Dr Gao said that with MPs as an emerging contaminant, it is important to get a better understanding of them, their impact and their removal.

“We have to remove them, and we have to provide the best quality of recycled water. This research helps South East Water and the water industry at large achieve better outcomes and supports a circular economy.” The research outcomes have so far resulted in two articles published in high impact peer-reviewed international journals.

South East Water has already adopted the research outcomes for the risk management of emerging contaminants and strategic planning for the company’s future water recycling facilities. The South East Water and RMIT research has already had significant economic, environmental and social impacts, with the findings likely to reframe how the Australian water industry will meet the challenges of emerging contaminants.

If you’re a water professional and want to learn more, you can contact Dr Li Gao on Li.Gao@sew.com.au

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