Can Tiny Bubbles Help Keep Microplastics Out of Our Waterways?

Australian researchers captured 95% to 97% of two common plastics in laboratory tests. The result is promising, practical and a reminder that the best place to tackle plastic pollution is still before it enters the water.

Once plastic breaks into particles too small to see, stopping it becomes much harder. Microplastics can move through drains, wastewater systems, rivers and oceans, which is why researchers are looking for better ways to catch them before they travel any further.

A team at RMIT University has now tested a deceptively simple idea: use two different sizes of air bubble together. In laboratory experiments, the combined system removed 95% of polyethylene particles and 97% of polystyrene particles from synthetic wastewater.

Those results are encouraging. They are also specific. The researchers tested 100-micrometre particles of two plastic types under controlled conditions. The process has not yet been proven across the jumble of fibres, fragments, sizes and chemicals found in a working wastewater plant.

That distinction does not make the research less exciting. It tells us exactly what has been achieved, and what still needs to happen next.

What the Study Actually Found

Sources: RMIT University and the published study.

How Can a Bubble Catch Plastic?

The process is an enhanced form of dissolved air flotation, a water-treatment method already used to separate suspended material from water. Air bubbles attach to contaminants and carry them to the surface, where the floating material can be skimmed away.

In the RMIT system, each bubble size has a different role:

• Microbubbles provide lift. They attach to plastic particles and help carry them towards the surface.
• Nanobubbles improve contact. Their much smaller size increases bubble-particle interactions and helps the plastics gather into larger groups.

Used together, the two bubble sizes outperformed either one on its own. Dissolved organic matter and fats, oils and grease did not reduce performance in the experiments. With standard coagulants present, they sometimes helped the plastic form larger, more buoyant clumps.

One reason the research stands out is practicality. RMIT says the approach could be adopted without major infrastructure changes by adjusting operating conditions such as air pressure, saturation time and bubble size. For plants that already use dissolved air flotation, that may make the technology easier to trial than an entirely new treatment system.

Why this matters  The method aims to improve a treatment process already used in many facilities, which may make future trials and upgrades more practical.

Capture Is Not the Same as Making Plastic Disappear

But there is an important catch: captured plastic has not disappeared.

The material skimmed from the surface still needs to be contained and managed safely. Otherwise, a treatment plant can shift microplastics from water into another waste stream. This matters because particles captured during wastewater treatment can become concentrated in sewage sludge or biosolids and may return to the environment later.

Before the dual-bubble method can be described as a real-world solution, field trials will need to answer some practical questions:

• Does it perform as well in real wastewater, across changing seasons and loads?
• Can it capture different particle sizes, shapes and polymers, including textile fibres?
• What are the energy, chemical and maintenance costs at full scale?
• How will the plastic-rich material be handled after it is skimmed away?

This is where careful science matters. A strong laboratory result is the beginning of the story, not the end.

The Plastic Hiding in Our Wardrobes

Wastewater technology deals with plastic after it has entered the system. Our wardrobes help determine how much enters that system in the first place.

Polyester, nylon and acrylic may feel like fabric, but they are plastic polymers. The latest Materials Market Report from Textile Exchange shows just how dominant one of those materials has become: polyester accounted for 59% of total global fibre production in 2024, and 88% of that polyester was fossil-based. These figures cover fibre used across apparel, home textiles, footwear and other applications, not clothing alone.

Synthetic textiles can release tiny plastic fibres during manufacturing, everyday wear, washing and disposal. Estimates of their share of marine microplastic pollution vary because measuring particles this small is difficult and methods are not yet standardised. Even so, both the United Nations Environment Programme and the European Environment Agency identify synthetic textiles as a significant source.

It is also worth being precise about the language. Natural textiles such as hemp and cotton shed fibres too, but plant-based cellulose fibres are not plastic. Finished natural-fibre garments are not automatically impact-free, however. Dyes, coatings, trims, farming, processing and transport all matter, and a blended fabric may still contain a synthetic component.

Recycled polyester deserves the same clarity. Using recycled feedstock can reduce demand for virgin fossil material, but recycled polyester is still plastic and can still release plastic microfibres.

A useful label check  Polyester, recycled polyester, nylon, acrylic and elastane are synthetic plastic fibres. Hemp, cotton, linen and wool are natural fibres. Lyocell and viscose are regenerated cellulosic fibres made from plant-derived cellulose.

What Is Australia Doing?

Australia has recognised the problem at policy level. The Australian Government's National Plastics Plan states that it will work with the textile and whitegoods sectors on an industry-led phase-in of microfibre filters in new residential and commercial washing machines by 1 July 2030.

That is a policy commitment, not a reason to wait. There are useful choices we can make now without throwing away perfectly wearable clothes.

Six Practical Ways to Reduce Laundry Microfibres

No single action will solve microplastic pollution, but a few habits can reduce unnecessary fibre loss and help clothes last:

• Keep what you already own. Do not discard a useful synthetic garment simply because it is synthetic. Wear it well and keep it in use.
• Read the full fibre label. Look past words such as "eco", "performance" and "recycled" to see exactly what the garment contains.
• Choose natural fibres for everyday basics. T-shirts, shirts, socks, sleepwear and relaxed layers are straightforward places to reduce plastic-heavy fabrics.
• Wash only when needed. Where garment care allows, use a full load, a shorter cycle and a lower temperature. Washing conditions and abrasion affect fibre release.
• Consider a fibre-catching device. An external filter, in-drum device or purpose-made wash bag can reduce what reaches the drain, but results vary between products.
• Put captured lint in the bin. Do not rinse collected fibres down the sink. Seal them with household waste so they are less likely to escape.

Independent testing has shown why careful wording matters here too. In one study of six laundry devices, the reduction in fibres reaching wastewater ranged from 21% to 78%. A filter or wash bag can help, but performance differs and captured lint still needs to go in the bin, not back down the drain.

Why Hemp Belongs in the Conversation

Hemp belongs in this conversation because it offers a plant-based alternative for many of the everyday garments now commonly made from plastic-heavy fabrics.

Hemp is valued for strength, breathability and the way it softens with wear, making it well suited to clothes designed to be reached for again and again. Choosing a hemp-rich T-shirt, shirt, pair of pants or layer can reduce the amount of plastic in that part of your wardrobe.

We also believe the label should do the talking. Some hemp garments are blended with cotton or plant-derived cellulosic fibres for drape and softness. Others may include a small percentage of elastane where stretch is needed. A product containing hemp is not automatically plastic-free, so check the full fibre composition and choose what suits the garment's job.

The most sustainable wardrobe is not built through perfection. It is built by buying thoughtfully, caring for what we already own and choosing materials that can stay in use for a long time.

The Bigger Picture

RMIT's tiny bubbles are a hopeful piece of a much larger puzzle. Better wastewater treatment can catch more plastic at the end of the pipe. Washing-machine filters can intercept some fibres in the laundry. Better textile design and more considered material choices can reduce what enters the system at all.

We need progress at each point. The treatment plant matters. The washing machine matters. And the small moment when we turn over a garment and read its fibre label matters too.

Ready to bring more natural fibres into your wardrobe?

Related reading: How Did We All End Up Wearing Plastic?