Bio beads are small plastic pellets used in wastewater treatment plants to help bacteria break down sewage, but they are also an emerging microplastic pollution problem in rivers and seas.

What bio beads are

  • Bio beads are tiny, usually about 5 mm, irregular plastic pellets made mostly from polyethylene.
  • Their rough or dimpled surface gives bacteria a place to grow, forming a biofilm that helps clean wastewater in aerated treatment tanks.

How they are used

  • In many sewage works, liquid effluent is pumped through large tanks filled with bio beads, where bacteria living on the beads digest remaining organic matter.
  • This process is often called Biological Aerated Flooded Filter (BAFF), and bio beads act as a lightweight “biomedia” providing a huge surface area for microbes.

Why they are a problem

  • When systems fail or pellets escape during handling, bio beads can spill into rivers and coastal waters, where they behave like other microplastics.
  • Wildlife can mistake them for food; ingested beads can block or damage the gut and may carry high levels of chemicals like PAHs and heavy metals on their surface.

Current attention and debate

  • Recent spills in the UK have led to clean‑up operations, media coverage, and community beach surveys documenting large numbers of bio beads on shorelines.
  • Regulators and researchers are discussing alternatives (such as different filter media or treatment technologies) and tighter controls to prevent further releases.

Information gathered from public forums or data available on the internet and portrayed here.