Pollution by anthropogenic microfibers in North-West Mediterranean Sea and efficiency of microfiber removal by a wastewater treatment plant
This latest article aims to study the transport of synthetic microfibers from urban areas to the sea. While very few publications had done so until now, the atmospheric input has been quantified. These results add to numerous studies characterizing microplastics in different environmental compartments.
Several figures stand out in quantifying this pollution:
- For samples in the marine environment
14 to 50% of the fibers in the samples were synthetic.
Between 35% and 72% were of natural origin (cotton and wool) or derived from processes using natural fibers (cellulose). These figures are slightly higher than those for textile production, where more than half of global production is based on plastic polymers, with 49% based on polyester alone.
- In wastewater
Among synthetic fibers, polyamide (30%) and polyester (22%) are the polymers most commonly found in wastewater.
At the outlet of wastewater treatment plants, polyester fibers are the main source of pollution and contribute more to marine pollution than microplastics resulting from the fragmentation of larger plastics.
One of the most surprising findings was the presence not only of polyamide and polyester microfibers, but also of polypropylene and acrylic.
- Fiber path
Depending on their size, fibers are transported along different routes: shorter fibers are carried through the air, while longer fibers travel through wastewater. This means that the smallest microplastics can persist and be transported in the atmosphere, deposited and inhaled continuously, thus posing a long-term threat to ecosystems and human health.
Estimated aerial deposition of microplastic fibers in the Mediterranean: 392 microfibers per square meter per day.
- Fiber processing efficiency
3 to 99 fibers per gram of clothing are released during machine washing.
The inflow to the Haliotis wastewater treatment plant (Nice) is 858,000 fibers per m3.
The outflow from the Haliotis wastewater treatment plant (Nice) is 8,100 fibers per m3.
The plant’s microfiber treatment efficiency varies between 87.5% and 98.5%, depending on the month and the clothing worn and washed.
Despite these high figures, 4.3 billion fibers enter the marine environment every day at the plant’s outlet.
Understanding the sources and dispersion of these microfibers is essential for developing more effective policies to treat and prevent this pollution. Coastal urban areas have water treatment systems that vary greatly depending on the type of pollution to be treated. In addition, once the particles have been recovered from the wastewater, they are then recycled via sludge used as fertilizer. The microparticles therefore also end up, through leaching, in rivers and the aquatic environment.