Blue-green algae

Goulburn Valley Water / Water / Water Quality / Blue-green algae

Blue-green algae (cyanobacteria) are a type of microscopic, algae-like bacteria which inhabit most aquatic systems including streams, lakes, estuaries and the sea. There are many different species (toxic and non-toxic) and hot sunny days, increased nutrient levels and still weather conditions can provide optimal conditions for them to flourish – rapid growth can create a ‘bloom’ on the water’s surface. Blooms mostly occur in warmer weather (spring, summer and early autumn), but they can happen any time if conditions are favourable.

Blue-green algae can affect water quality, however we have treatment processes in place to ensure the continuous provision of safe and reliable water. Sometimes higher levels of blue-green algae can create an ‘earthy’ taste or odour in treated water, but the water remains safe to drink – we’ll always let you know if that changes.

All drinking water supplied to customers meets the Safe Drinking Water Act 2003 and the Australian Drinking Water Guidelines. We continually monitor and assess the water quality, and samples are regularly sent to an independent laboratory for testing. We also work closely with Goulburn-Murray Water, which manages a number of waterways from which we source water.

Blue-green algae in the Yarrawonga Weir in 2020.

Current blue-green algae detections

EUROA
Goulburn Valley Water is aware of a taste issue Euroa's drinking water supply, which is associated with a detected an algal bloom in a high-level catchment in the Euroa supply system at Waterhouse Reservoir. The bloom was detected on October 15 and sampling at all water storages and at the treatment plant was immediately carried out.

To address the taste, we have changed our process to source water from an alternate water storage in the short term, and we’ve optimised the treatment process at the Euroa Water Treatment Plant to remove as much of the taste and odour as possible. The treatment optimisation includes treating the water using powdered activated carbon, which is very effective at removing taste and odour compounds. Operators are continuing to optimise the different carbon varieties and rates to remove taste and odour compounds.

Our water quality testing at the plant is currently showing no indications of algae in the raw water inflows since switching to the alternate water storage. The new water source and treatment has already created significant improvement in the treated water supplied by the plant, and we expect the taste and odour to continue to improve over the next couple of days.

We know these occasional taste and odour issues are undesirable and we’re really sorry for any disruption or inconvenience. Our water quality specialists continue to monitor and respond to any changes in the water supply.

Sometimes, these algal blooms can cause an ‘earthy’ taste or odour in the water. Algal blooms can last for weeks or months, depending on weather conditions. Some people may notice changes in taste and odour more or less depending on sensitivity to water changes, or due to timing of fresh treated water coming through the plant and into various parts of the distribution network.

LONGWOOD
We have also detected a blue-green algae bloom in the raw water supply for Longwood in the Nine Mile system, which is creating an earthy taste and odour in Longwood's drinking water supply. We are working to optimise the water treatment plant operations, including replacing the activated carbon filtration media which should help to remove more of the taste and odour compounds caused by the algae.

We'll continue assessing the water quality and continue working to improve the water taste and odour. We know these occasional taste and odour issues caused by seasonal impacts are undesirable and we're really sorry.

Regulated (non-potable) supplies

Goulburn Valley Water supplies several towns with non-potable (non-drinking) water supplies. We recommend these customers have an alternate supply of drinking water.

Potable (fully treated) supplies

We regularly monitor for blue-green algae in our raw water supplies. Our water treatment plants remove algae and dissolved compounds as part of the treatment process before the water reaches your taps.

FAQs - blue-green algae and water treatment

The majority of our raw water is sourced from the Goulburn and Murray Rivers, their associated tributaries, and irrigation channel systems managed by Goulburn-Murray Water. In recent years, water storages on both the Goulburn and Murray River systems have experienced blooms of blue-green algae that have impacted on the water quality.

What are blue-green algae?

Blue-green algae are not algae, but bacteria that are a natural part of aquatic systems. They come in a range of shapes and sizes and can be free floating in the water or live on rocks and vegetation at the bottom of waterways. Although the single cells are microscopic, some species of blue-green algae form colonies or filaments that can join and are visible to the naked eye; forming pea shaped masses, or paint like algae slicks at the water’s surface in many unusual colours including green, blue, red, brown, white or yellow. At other times, the sheer volume of blue-green algae in a waterway may turn the water a deep green but not produce surface scums.

How can blue-green algae affect drinking water?

Different species can be toxic or non-toxic and can produce taste and odour causing compounds such as geosmin and 2-methylisoborneol. These compounds have a strong, unpleasant earthy or musty taste and odour that can be detected at extremely low levels, as low as 0.00001 mg/L. In comparison, chlorine can generally be tasted between 0.1 and 0.4 mg/L. At high levels, it can be difficult to remove all taste and odour from the treated water.

Blue-green algae and the water treatment process

We use many treatment technologies to remove algae, particulates, and dissolved compounds from surface water. To remove compounds that cause taste and odour we use activated carbon (powdered or granulated), which is added pre-treatment and then removed along with the algae cells and other dirt as part of the filtration processes. Activated carbon is extremely porous and absorbs taste and odour compounds onto its surface.

Even though not all toxic species of blue-green algae will produce toxins, we proactively use a range of water treatment processes to remove any potential toxins and ensure water is safe to drink This includes:

managing our access points to raw water sources
pre-treating with carbon
removing algae cells intact
using coal and fine sand filters
oxidising the water to destroy any toxins that might be present.

How long will blue-green algae impact on water quality?

There is no way to predict how long a bloom might last and there is no easy fix.

Blue-green algae grows when a combination of favourable conditions, including temperature, light and nutrients are present. Blooms develop rapidly when the conditions are right, followed by a stable period called the plateau phase after which the cells start to die off. Once the bloom has plateaued, it can remain for weeks or months if environmental conditions are still right. Compounds causing taste and odour can remain in the water for extended periods of time, even after the bloom has died off. This means some people may notice lingering taste and odour in the drinking water for quite some time.

Is there anything I can do to improve the taste?

We know taste and odour can be frustrating – we’re sorry. Some people have reported that putting water in a jug in the fridge can help with any taste and odour issues. You could also consider adding lemon or fruit wedges (orange, mint, watermelon, etc) to help.

I have a concern or enquiry about water quality, who do I contact?

While we’re always working to optimise our treatment processes to improve the taste and odour, blue-green algae can be unpredictable. Sometimes these taste and odour events occur without our knowledge, such as when a bloom occurs extremely high up in the water catchment and releases taste and odour compounds that move downstream while the blue-green algae remains behind.

If you’re a Goulburn Valley Water customer and you notice a change in your water supply or you have an enquiry, please contact us on 1800 454 500 at any time, or report it online.

If you are supplied by Goulburn-Murray Water (irrigation or stock and domestic supplies) you can find more information at their website.

Recreational warnings

Recreational warnings are issued by Goulburn-Murray Water and Water NSW and do not relate to the quality of drinking water supplied by us. Recreational users should be aware of alerts which can be found at:

https://www.waternsw.com.au/water-quality/algae

https://www.waternsw.com.au/water-services/water-quality/algae-alerts

https://www.g-mwater.com.au/water-operations/bga

https://www.g-mwater.com.au/water-resources/water-quality/blue-green-algae

Blue-green algae in the Goulburn River in 2019.