Blue-green algae FAQ

Blue-green algae are naturally occurring bacteria found in waterways and water storages including dams and weirs. Hot weather and still water provide ideal conditions for algae to grow and cause blooms.

Some algae can produce taste and odour and occasionally toxic compounds. These compounds are dissolved in the water and invisible to the eye.

Blue-green algae does not effect the safety of treated drinking water supplies. Our treatment plants have processes in place to remove any toxins as well as the taste or odour associated with the algae.

Sometimes when algae levels are at high levels, there can still be a slight earthy taste to treated drinking water. This water is safe to consume.

Blue-green algae can sometimes cause a naturally occurring compound called Geosmin in the raw water supply. Geosmin has a very strong, earthy taste and odour. It can be smelled at very low concentrations (in the parts-per-trillion range).

When levels of blue-green algae and geosmin are at very high levels, it can be difficult to remove all the taste and odour from drinking water. Although the water may be unpleasant to taste, it is still safe to consume.

Learn more about Gesomin

We use treatment barriers and processes to ensure that algae does not affect the safety of drinking water. Coagulation and filtration is used to remove algae cells from the water and powdered activated carbon is used to remove any toxins and taste and odour causing compounds that may be dissolved in the water.

Extensive testing is conducted on treated water to ensure that the water is safe to drink.

We maintain a monitoring program in areas across our service region prone to algal blooms. Water samples are collected and analysed by our external contracted laboratory. Identification and enumeration of the particular algae allows us to adjust the treatment process to suit.

Recreational warnings may be issued by Goulburn-Murray Water or Water NSW during blooms advising water users to avoid contact with water in storages.

While important, these recreational warnings do not relate to the quality of drinking water supplied by North East Water. Our treatment plants have processes in place to remove any toxins and the taste or odour associated with the algae.

It is not possible to predict how long the blue-green algae will last in the raw water. Once an algae bloom declines, there may still be high levels of geosmin in the water afterwards. However, as the weather cools, geosmin levels typically decrease, reducing taste and odour issues in drinking water.

Goulburn Murray Water

Water NSW

Department Environment Land Water and Planning

Current warnings can be found on the Goulburn Murray Water website or the Water NSW website.

You can also phone GMW’s blue-green algae hotline on 1800 013 357 or Water NSW on 1800 999 457.

Warning signs are placed at major recreational areas in Victoria and NSW.