Biomedia pollution

Biomedia, used in many wastewater treatment plants since the early 2000s, can today be found on beaches all over the world in large quantities. Surfrider Foundation Europe has now published its first report on this subject, following 10 years of research.

Download the report

In 2007, Surfrider volunteers in France started to notice plastic cylinders measuring about 1 to 4 cm across turning up on beaches in the Bay of Biscay. Their investigations revealed that these objects were bacterial biofilm carriers  (biomedia) used in wastewater treatment plants. The discs, a few millimetres thick, act as a base structure for the growth of microorganisms used to digest suspended matter in wastewater.

The little plastic wheels are not supposed to leave the wastewater treatment tanks. However, malfunctions or technical incidents can unfortunately lead to huge numbers of them entering the environment.

Numerous biomedia pollution incidents have been observed since 2007 along large stretches of European riverbanks and coasts

Monitoring pollution incidents

After studying this issue for 10 years, Surfrider Europe (SFE) has become the leading NGO working on this pollution problem. The NGO has published several press releases on the issue and been referred to in many press articles and reports. SFE has documented various pollution cases on the Seine in France and on the Miño river in Portugal. In Switzerland, biomedia have been collected along the banks of Lake Geneva, originating from wastewater plants in Saillon, Evolène and Saint Prex. In the United States, beaches and water courses have been polluted by biomedia from wastewater treatment plants in Hooksett, Groton and Mamaroneck.

10 major pollution incidents                                        25 Different models                                                     1,000 Reports

A holistic analysis of the problem

We have visited wastewater treatment plants, spoken to numerous industry experts, and spent time on the ground in order to gain an understanding of operations at wastewater treatment plants using biomedia. We have compared the known incidents, enabling us to draw up recommendations aimed at preventing further discharges of biomedia into the environment.

What are the main causes of malfunctions?

The observed pollution incidents have generally been caused by a combination of various factors, including:


  • Overflows as a result of heavy rain,
  • Losses during commissioning or maintenance work on the treatment tanks,
  • Blockages caused by insufficient agitation of the biomedia,
  • Unsatisfactory storage
  • Unregulated installations
  • Water outlet grates that are not designed to be used with the biomedia process…

… but solutions to prevent pollution incidents can be simple and cost effective:

  • Prevention and information on specific aspects of biomedia use
  • Guidance and support for users during the process start-up phases,
  • Fine tuning of aeration and de-clogging systems,
  • Implementation of procedures to recover lost biomedia in the event of an incident

All this information, along with numerous maps, diagrams and photos, can be found in our report, which can be downloaded for free. Read and share…


Download the report


How can I submit a sighting?

Please get in touch if you have found wastewater treatment biomedia on the banks of a watercourse or on a beach by sending your testimony! You can also send an email to , telling us the date, place and number of biomedia found. And remember to attach a photo too, because there are so many different models!



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Cette étude est cofinancée par la Commission européenne. Néanmoins les analyses et opinions présentées dans cette étude n’engagent que leurs auteurs. This study is co-funded by the European Commision. However, the analyses and opinions presented in this document are those of the authorrs.