UN Environment - A lot of attention has been drawn recently to microplastics in freshwater and marine environments, and the threat they pose to ecosystems and people’s health.


The source of microplastics is generally thought to be well known: most plastic items are not recycled or incinerated when they are discarded. Plastic waste therefore ends up in landfill or in our rivers and oceans where it gradually breaks down into smaller and smaller pieces and particles. Microplastics are defined as pieces of plastic 5mm in diameter or less.

A new study, however, concludes that treated sewage effluents are also key sources of microplastics – the implication being that wastewater treatment plants are not effective at filtering them out.

Published in July 2018, a study in the United Kingdom titled Wastewater treatment plants as a source of microplastics in river catchments looked at six river catchments in the north of England.

“The fact that the quantity of microplastics present in receiving waters was greater downstream of each of the six wastewater treatment plants studied confirms that treated sewage effluent is a key source of microplastics,” concluded the authors.

The study also found microplastics upstream of water treatment plants. These, in turn, come from sewage sludge applied to agricultural land as fertilizer, the diffuse release of secondary microplastics, and aerial deposition.