Is It Sewage or an Algal Bloom? Here’s How to Tell

As summer heats up, South West Water addresses common misconceptions about algal blooms in coastal and inland waters.

Algal Blooms or Sewage? Understanding the Difference

As temperatures rise and more people head to the South West’s picturesque rivers and coastline, reports of what appear to be pollution incidents start flooding in. However, Helen Dobby, Head of Environmental Performance at South West Water, is keen to clarify that many of these reports are actually sightings of algal blooms—a natural phenomenon that is often mistaken for sewage.

Algal blooms typically occur between April and August, though they can form out of season if conditions are favourable. The blooms are composed of naturally occurring algae, which thrive in the warmer temperatures and increased sunlight. These blooms can sometimes form clouds resembling frog spawn or oil droplets in the water. As the algae break down, they can create a creamy brown-coloured foam that may persist on beaches for a day or two, eventually degrading into scum-like patches.

This foam, which can range in colour from white to brown depending on the sediment trapped within, often raises alarm due to its resemblance to sewage. Compounding the confusion, the decomposition of algal blooms can emit an unpleasant odour, akin to the smell of rotten vegetables or a musty scent, further fuelling concerns among beachgoers and residents.

Spotting the Signs: Algal Bloom vs. Sewage

Helen explains that understanding the signs can help differentiate between an algal bloom and a sewage spill. While algal blooms are a natural occurrence and often appear as foamy patches on the water’s surface, stormwater overflows, in contrast, usually cause a grey discolouration of the water. These overflows often have a clear source, such as a pipe or outfall, where the discolouration is most pronounced. Treated sewage discharges and stormwater overflows rarely produce foam on the water surface.

One important distinction to note is that while washing powders and detergents can cause localised foaming around discharge pipes, particularly near surface water outfalls, they do not create the long lines or thick blankets of foam typical of algal blooms.

The South West’s Bathing Water Quality

Despite the concerns that can arise during algal bloom season, the South West boasts some of the best bathing waters in Europe. According to the Environment Agency, almost all of the region’s 860 miles of coastline have a ‘good’ or ‘excellent’ water quality status. Moreover, for the past three years, all bathing waters near storm overflows that could impact water quality have passed stringent quality standards.

To keep the public informed, South West Water has launched the WaterFit Live map, which provides real-time information about the region’s bathing beaches. This tool allows users to see when storm overflows have been activated, giving them confidence in the quality of the water.

What to Do If You’re Concerned

South West Water urges anyone who spots something unusual or concerning in the water to report it immediately. Helen reassures the public that the company is deeply committed to protecting the natural environment and will investigate any potential issues with their network promptly. Concerns can be reported by calling 0344 346 2020 or via the South West Water website.

As the summer continues, being informed and vigilant can help everyone enjoy the South West’s beautiful waters safely and confidently.