Consumer Concerns

Algal blooms and effects on water quality

Rivers and lakes can support a wide range of plants, including algae which are tiny free floating green plants. Intense algal booms can occur under certain conditions and when the plants die off scums may form at the margins of the lake or reservoir. The scums associated with blue-green species of algal (Cyanobacteria) contain toxins that can cause serious irritations by skin contact and can cause death if animals ingest algae laden water. When such bloom occur water companies post warning notices at reservoirs where recreational activities are permitted on the need to avoid water contact.

Cases of algal toxin poisoning via drinking water have been reported from other parts of the world and especially in Australia and the Far East. However, these events have occurred in extreme climatic conditions and in water supply systems without adequate water treatment.

Following serious algal blooms in 1989 and 1990, which resulted in animal deaths at a lowland reservoir in Eastern England, the water industry and the Government commissioned research into the toxicity of blue-green algae and the effectiveness of water treatment. The studies confirmed that seasonal occurrence of toxic algae in water supply reservoirs was not uncommon. The study also confirmed the effectiveness of disinfection, flocculation and filtration treatment provided in completely removing algae and any dissolved algal toxins from water sources. Furthermore an intensive survey of algal toxins in drinking water supplies throughout the UK that was carried out under optimum climatic conditions for production of blue-green algae, failed to detect algal toxins in any drinking water samples.