Despite the name, blue-green algae are not really algae at all. In fact, they’re a type of bacteria that naturally occur in inland waters, the sea and on bare rocks. Blue-green algae thrive in nutrient rich water, warm weather and long hours of sunshine. It’s in these conditions they will often form a visible scumor mat on the surface of the water known as blooms. These can be green, red, brown and turquoise in colour.
Some species can produce toxins, however it’s impossible to predict the amount produced in each bloom. These toxins can be fatal to wild animals, aquatic life and domestic pets, so always keep an eye on your dog when walking near water. They can also be harmful to humans if ingested or touched, resulting in vomiting, fever, sore throat, muscle and joint pain, skin irritation and even liver damage. That’s why it’s important to take great care during recreational water activities and when visiting our reservoirs.
There’s no evidence to suggest that harmful levels of toxins occur in treated drinking water within the UK. What’s more, it’s been shown that modern water treatment processes used to treat surface waters in the UK can remove or destroy any blue-green algal toxins that might remain in untreated water. In the few Severn Trent raw water sources subject to algal blooms, we avoid drawing untreated water contaminated by algae into the works. We do this by switching to an alternative source, obtaining water from deeper in the reservoir, or avoiding the surface layers where the algae are abundant.