Take a look around you. Nearly everything you see contains plastics. They are everywhere. Of all the plastics though, the most alarming in terms of the devastating effect they are having on marine life and infiltrating our lives through the aquatic environment food chain, is microplastics.

Microplastics are defined as pieces of plastic 5 millimetres in diameter or less. They include microbeads in personal care products like facial scrubs, microfibres in polyester fabric, and larger plastics that have broken down into smaller pieces and are unable to be extracted by our cities’ wastewater treatment plants.

Microbeads can be found in personal care products like facial and body scrubs, and in abrasive cleaners

On Aurecon’s Just Imagine blog in June 2018, small plastics were highlighted as a big problem. These are the plastics that we don’t see, that are damaging the world we live in.

This thinking paper considers the impact of microplastics as they enter wastewater treatment plants. Our wastewater treatment plants currently have limited capacity to extract microplastics from wastewater. So, what could be the answer on filtering these contaminants to help the future of our waterways?

What we know about microplastics

A great deal of attention has been drawn recently to microplastics in freshwater and marine environments, including a recent publication “Plastics Pollution in the World’s Oceans" by oceanographer Dr Marcus Eriksen. The study investigated which kinds of plastic were most polluting the oceans. To the researcher’s surprise, significantly outnumbering bigger plastic items such as toothbrushes and the balls in deodorant roll-ons, were confetti-sized and smaller shreds of plastics.

According to the United Nations Environment Programme, microplastics not only contribute to the accumulation of plastics in the environment but, due to absorption, they can also contribute to the spread of micropollutants in the environment. Microplastics can act as a vehicle for the dispersal of harmful chemicals and bacteria. These chemical-laced particles can be ingested by small organisms, bigger marine animals, and then further on up the food chain and onto our plates.

This is an area that deserves research attention to truly understand the fate and toxicity of microplastics in humans as we eat, drink and breathe.

How microplastics are making their way into the oceans and waterways through wastewater treatment plants

Microplastics in the water system

Once microplastics enter the wastewater system they make their way into our wastewater treatment plants.

A recent study by the International Water Association concluded that wastewater treatment plants (WWTPs) were not adequately preventing microplastics from entering the marine environment due to the current limited technologies to extract tiny microplastics from the wastewater.

The results showed that microplastics may be released into the environment in two main ways:

• Sludge land application, as sludge is removed from wastewater treatment plants and used as commercial fertiliser on agricultural land
• Plastic fibres, fragments and flakes, as well as pellets and beads, pass through the filtration process because there is no specific technology to remove microplastics from the wastewater

Research is underway, looking into wastewater treatment technologies to remove microplastics at different stages of the wastewater treatment process. In the future, wastewater treatment plants might play a critical role in stopping microplastics from entering our marine ecosystem and affecting people’s health.

However, industries and human activities are the main contributors and the real solution to stopping the dispersal of microplastics from entering our aquatic environment is stopping them entering the wastewater in the first place.

There’s still a way to go

The current efforts to remove microplastics at WWTPs are preliminary and limited to research only. This is largely due to the lack of microplastic characterisation, with research in its infancy.

Existing characterisation methods lack measurement accuracy on very tiny microplastics and the differentiation between types of microplastics.

Nevertheless, researchers around the world are investigating the options for microplastic-specific treatment technology for WWTPs.

Research is being conducted into the potential of filtration and membrane technology for effluent treatment, as well as thermal technology (pyrolysis and gasification) for microplastic- contaminated biosolid treatment. This type of technology would work by filtering out microplastics during the biosolids stage of the treatment process.

To address the future of microplastic-pollution it will take a collective effort and research is a major part. But, the most important actions to reduce the volume of microplastics entering the water system every day include:

• Public awareness and education so people choose to avoid plastic products and opt for compostable products instead
• Manufacturers reducing single-use plastic production and introducing compostable items
• Governments, industry and entrepreneurs developing systemic, more innovative, and more audacious solutions that reduce plastic use and prevent plastic from becoming waste in the first place
• Cities introducing more innovative plastic waste recycling systems
• Environmental regulators taking further action to ban single-use plastic bags and other plastic items
• Governments investing in innovative plastics reduction and recycling as well as clean-up programmes

Each and every one of us has a role to play, as a consumer, engineer, designer, researcher or influencer, in reducing the big problem of these small pollutants.

As research continues into wastewater treatment technology, and the effect microplastics have on our oceans is publicised more and more, technological innovations will surely follow.

Anything we do to reduce, reuse and recycle will make a difference. With human populations worldwide changing their plastic-using ways and demanding that manufacturers do as well, we might just be able to reverse some of the damage that’s been done during past decades.

About the Author

Shao Yap is a Process Engineer in Aurecon, working as a member of the Queensland Water and Wastewater team. Primarily assisting the process engineering team in investigation, planning, concept and feasibility studies, Shao has a strong interest in the integration of environment and safety into sustainable business that looks beyond box-ticking compliance and the bottom line.