Action needed to prevent Earth from becoming a plastic planet

CST Wastewater Solutions

Monday, 13 February, 2023

Action needed to prevent Earth from becoming a plastic planet

Seven years back, a marine biologist filmed a sea turtle with a straw stuck up its nostril. The video went viral and drew global attention to the plastic polluting our oceans. That visual served as a catalyst and helped accelerate the move away from single-use plastics in many parts of the world. But there’s also plastic that cannot be seen and these microplastics find their way into our waterways, soil, livestock and aquatic life, and eventually into humans.

A recent study commissioned by World Wildlife Fund for Nature (WWF) revealed that humans could be consuming 5 g of microplastics each week. That equates to the weight of a credit card, according to University of Newcastle, which conducted the research for WWF.

Littering and inadequately managed waste are often considered amongst the main causes of plastic waste. While large pieces of plastic waste are readily visible, research studies now indicate that microplastics are a growing area of concern. While wide awareness about some forms of visible plastic pollution such as straws and grocery bags is leading to bans in many jurisdictions, it will be more difficult to legislate against microplastics.

Plastic pieces measuring less than five millimetres across are considered microplastics and are often created by the fragmentation of large plastic pieces over time. Primary microplastics are also mass-produced when manufacturing abrasive cleaning agents, plastics manufacturing and plastic powder for moulding.

Cosmetic microbeads used in facial scrubs are also a significant source of microplastics. The fashion industry too is coming under scrutiny and is considered the largest source of primary microplastics accounting for close to 30 to 40% of the global microplastics pollution.

Laundry wastewater is a major source with synthetic textiles in particular releasing acrylic, nylon and polyester microfibres. With every wash, synthetic fabrics release microfibres which are similar to microbeads found in cosmetics. A garment can release 700,000 fibres in a single wash.

Scientists are only beginning to understand the effects of synthetic textile waste. Microfibres are the major marine pollutant throughout the world, with an estimated 13 million tonnes of coastal synthetic fabric waste entering the ocean each year. The adverse impact on animal life is significant. Australian researchers have discovered that zooplankton exposed to microplastic fibres produced half the usual number of larvae and that the resulting adults were smaller.

Microplastics are also extremely persistent, and it is close to impossible to remove them once they find their way into the environment. Plastics smaller than 100 nanometres are nanoplastics typically formed when microplastics are exposed to light at moderate temperatures. These can impact humans and animals at the cellular level, passing through cells and tissue. One study that deliberately let pregnant mice inhale extremely tiny particles later found them in almost every organ in their fetuses.

Microplastics from a variety of sources — manufacturing, textiles, laundry, industry — find their way into wastewater systems. Preventing the spread of microplastics would be the most beneficial and practical solution and it is important to look at the role that sewage plays in the distribution of microplastics. Between 80 and 90% of the plastic particles contained in sewage persist in the sludge, according to a UN study.

Sewage sludge is commonly applied to fields as fertiliser, and as a consequence, several thousand tons of microplastics end up in our soils each year and even in our tap water. Terrestrial microplastic pollution is much higher than marine microplastic pollution — estimated to be four to 23 times more, depending on the environment.

The surfaces of tiny fragments of plastic also act as carriers for disease-causing organisms and spread through the environment. Microplastics can also interact with soil fauna, affecting their health and functions. New research shows that the presence of microplastics can stunt the growth of earthworms, and even cause them to lose weight — potentially having a serious impact on the soil ecosystem.

Sewage is a significant distributor of microplastics with 80 to 90% of the particles contained in sewage, such as from garment fibres, persisting in the sludge. Sewage sludge is then often applied to fields as fertiliser and it has been estimated that several thousand tons of microplastics end up in our soils each year.

Scientists are racing to find solutions to clean up microplastics. There is work being done on magnetic liquids and plastic-eating mushrooms, but a viable mass-scale remedy is not yet in sight. Preventing microplastics from entering our environment, it appears, may be the best approach and the first and best line of defence currently.

CST Wastewater Solutions provides locally developed drum screen technology that can prevent blockages, overflows and environmental damage. “Our technology’s fine screening capabilities go down to 200 microns and can be implemented in municipal sewage systems and by industrial users,” said Michael Bambridge, Managing Director, CST Wastewater Solutions. “The horizontal drum screens will screen out a lot of microplastic you can see, which is a step towards addressing this significant environmental threat.”

CST’s horizontal in-channel rotary drum screening technology is locally manufactured and built to be both robust and adaptable. Compared with traditional screening at wastewater treatment plants, its in-channel technology has lower fluid head loss at peak flows to increase solids removal efficiency.

When dealing with fine screening of larger flows, the technology has the advantage of mechanical simplicity, self-cleaning and high-efficiency screening. This can result in reduced maintenance and lower whole-of-life costs compared with other types of screens, such as band and inclined drum screen designs.

There are growing calls for industry to close the plastic tap to prevent the oceans from becoming plastic soup. Effective wastewater screening can go a long way in alleviating the problem.

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