A German study has confirmed that conventional methods used at wastewater treatment plants do not completely eliminate microplastics.
Researchers from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) examined wastewater and sewage sludge from 12 treatment plants and were able to detect and classify plastic particles.
To do this, they employed micro-FTIR and ATR-FTIR spectroscopy, using infrared radiation to set molecular bonds into oscillation. Depending on the method, the scientists pressed particles onto a crystal for more detailed classification or placed them on an aluminum oxide filter in order to analyze them under a microscope. Through these methods they could identify the plastics and reliably differentiate them from natural materials.
The research project was commissioned by the regional water association of Oldenburg and Ostfriesland, Germany (OOWV) and the Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency (NLWKN).
"The study provides valuable findings about plastic residues that no one has obtained thus far. By applying state-of-the-art methods, it is now possible to specifically classify plastics, such as those used in toothpaste, cosmetics, fleece jackets and packaging, even in wastewater," commented OOWV managing director Karsten Specht.
However, it's not yet possible to determine whether the majority of the microplastic particles found can be traced back to cosmetic or household products, or whether they originate from another source, such as abrasion of pipes.
"The occurrence of microplastic particles varies considerably. There is an urgent need for further studies to enable comparability. And this not only applies to the wastewater of treatment facilities, but also in rivers that receive the wastewater," said microbiologist Dr. Gunnar Gerdts, who analysed the samples.
OOWV department manager Andreas Körner pointed out that additional studies are also necessary to determine how best to minimize the release of plastic particles into rivers and seas. He noted that most microplastic particles are collected through tertiary filtration, but said it would be better to do this at an earlier stage, i.e. during the production process.
