Warning over algae that can be mistaken for sewage

South West Water has said it commonly receives reports from customers confusing algae with sewage

People are being warned about algae that can naturally occur on water in the South West which can sometimes be mistaken for sewage.

South West Water said during the summer it is common for large blooms of naturally occurring algae to appear.

Helen Dobby, head of Environmental Performance, said this algae can sometimes be mistaken for oil drops in the water, which can grow rapidly in the warmer months.

She explained: "When the bloom breaks down, as the algae die, a creamy brown coloured foam can be formed."

Ms Dobby said this "foam" can persist for a day or two until it is washed away by the rain or tide.

She continued: "Often these blooms are mistaken for sewage because the foams can be white or brown in appearance, depending on whether they have any sediment trapped in the foam.

"Also, as the algal bloom breaks down it can create an unpleasant odour, often like rotten vegetables or a musty odour, which can also be mistaken for sewage."

The water company said it was common to receive reports from concerned customers and visitors who have seen algae in the water, believing it to be a sewage spill.

Difference between algae and sewage

According to Ms Dobby, algal blooms are identifiable as they can often be seen off headlands and lying parallel to the coast.

Most of the time there is no point of origin on the shoreline. In rough conditions, thick mats of foam may be created on the shoreline.

In contrast, stormwater overflows tend to cause a grey discolouration of the water and often have a clearly identifiable source, such as a pipe or outfall, where the discolouration is strongest.