Nurdles and Bio-beads

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What are nurdles?

Nurdles, sometimes called mermaid’s tears, are tiny pellets of plastic.

They come from many sources and most pre-production industry plastic is supplied in the form of tiny pellets.

What are BAFF media / bio-beads?

Plastic pellets are sometimes used as a filtering media at sewage treatment works. These are called biomedia, Brightwater media, BAFF media or bio-beads. Not all BAFF (Biological Aerated Flooded Filter) plants contain bio-beads – some have a mineral media and others have a fixed structural media.

South West Water has eight BAFF plants with bio-bead media across the region, some of which are inland. The smallest serves a population of 1,200 and the largest, at Plympton, serves a population of around 85,000.

There are at least 46 BAFF plants with bio-bead media in the country, which range in size and population served.

How can you tell the difference between nurdles and BAFF media?

The colour of BAFF media is determined by the supplier but they can be any colour including black, blue, white or mixed.

It is very difficult to positively identify the source of a nurdle in the environment. 

How do nurdles get into the environment?

Nurdles are tiny – less than half a centimetre wide – and can be spilt from containers or be lost down drains from plastic production or recycling plants.

What is South West Water doing do to prevent the release of bio-beads?

All BAFF plants that use bio-beads are fitted with mesh grating over the cells. Bio-beads are expensive and act as important filtering media in the treatment process, so we wish to keep them within the process units. Any escape of beads is unacceptable.

In 2017, we reviewed and updated the technical standard covering their use at our treatment works. This included requirements for storage of used and new beads. We conduct regular site inspections and have installed secondary containment stainless steel wedge wire, as an additional control measure, at seven of the eight the works with bio-beads. The exception is Marsh Mills in Plymouth, where work to install secondary containment measures is still ongoing.   

We use appropriate disposal methods which prevent the release of bio-beads into the environment at the end of their life.

How does South West Water monitor for the release of bio-beads?

The nature of bio-beads is such that any escape is immediately obvious as coloured beads float on tanks and accumulate in works return systems, or are captured by the secondary containment stainless steel wedge wire. Additionally media levels within BAFF sites are monitored to ensure levels remain optimal.

Is there an alternative to using these pellets in the treatment process?

For the eight sites across the region that are designed to run with plastic media there is no alternative media that would comply with the required buoyancy needed by that process. However many BAFF plants do not use plastic beads and there are no current plans to install new Brightwater BAFF plants across the region.