Ellon Biomedia Spill

In November 2022, a period of exceptionally heavy rainfall resulted in widespread flooding across parts of Aberdeen City and Aberdeenshire. During this extreme weather event, the sewage treatment plant in Ellon became overwhelmed, leading to the unintended release of large quantities of plastic biomedia into the surrounding environment. Thousands of these small plastic pieces were initially observed along the banks of the River Ythan, before being carried downstream to the estuary and adjacent beaches. Within days, reports confirmed that biomedia had dispersed widely along the coastline, with sightings extending from Rattray Head to Aberdeen Beach. 

The biomedia involved were small plastic discs measuring just over 1 centimetre in diameter and approximately 0.5 centimetres in depth. These items are commonly used in wastewater treatment systems, particularly within trickle filters, where they provide a large surface area for beneficial bacteria to attach and grow. These bacterial colonies play an important role in breaking down dissolved solids in effluent water during the treatment process. However, once released into the natural environment, the biomedia posed a significant plastic pollution issue due to their volume, durability, and widespread dispersal. 

In February 2024, staff from the East Grampian Coastal Partnership (EGCP) attended a public open day at the Ellon Sewage Treatment Centre, where Scottish Water provided information panels and guided tours for members of the public. These sessions provided greater insight into the circumstances surrounding the spill and outlined the operational changes that have since been implemented, regarding the use and management of biomedia filters at the site. Scottish Water reported that approximately 380 cubic metres of biomedia filters were installed in the aeration lanes at the Ellon treatment works as part of a wastewater treatment when an upgrade was completed in May 2022. On 17 November 2022, most of this material was either recovered or prevented from leaving the site; however, it is estimated that approximately 10 cubic metres escaped the facility and entered the River Ythan. Scottish Water acknowledged that this resulted in a significant environmental impact once the material dispersed through the Ythan Estuary and along the wider coastline. Due to the nature of the incident, it was not possible to quantify the exact number of individual biomedia pieces released. 

Following the incident, all of the remaining plastic biomedia were removed from the treatment tanks as a precautionary measure while a full investigation was carried out. The investigation did not identify a single root cause, but rather a combination of contributing factors, including the buoyancy of the biomedia, foaming within the aeration lanes, overcrowding of mesh screens linked to an engineering fault caused by blower shutdowns, and the extreme weather conditions associated with Storm Frank. Scottish Water initiated clean-up operations immediately, both within the wastewater treatment site and across affected coastal areas, including Newburgh Beach and Forvie Sands National Nature Reserve. 

Approximately 60 staff and supply chain partners were involved in the response, and it is reported that over £315,000 was spent on recovery and clean-up efforts. Activities included manual beach cleaning alongside the use of mechanical 15 equipment such as tractors and chain rakes to support the removal of biomedia from affected locations. Despite these efforts, biomedia filters have continued to be discovered periodically since the original spill, although generally in much smaller quantities. This reduction is largely due to the combined efforts of the treatment centre, local nature reserves, beach cleaning organisations, and many members of the public and local communities who have actively assisted with removal. However, on Saturday 6 December 2025, following a period of very high tides, thousands of biomedia filters were once again washed ashore along the Newburgh Estuary. In response, a clean-up was rapidly organised for the following day, with support from local villagers and the Newburgh and Ythan Trust. During this effort, over 4,500 biomedia filters were collected from a 300-metre stretch of shoreline in just two hours. 

These biomedia filters are extremely small and easily become trapped or buried within sediment, sand dunes, and organic material such as reed beds and seaweed. As a result, many are likely to have been missed during initial clean-up efforts or continue to be redistributed by tides and currents due to their buoyancy. EGCP and TTPT hope to continue discussions with SEPA and Scottish Water regarding the long-term presence and behaviour of biomedia in the environment and appropriate ongoing management responses.