Earthy Odour and Taste - Geosmin

Geosmin and Methylisoborneol (MIB) - Earthy or Musty Odour and Taste 

Seasonal increases in naturally occurring algae or bacteria in the dam, can sometimes cause odour and taste issues with drinking water, where the water is often reported as having an earthy or musty taste and smell.   This is due to harmless, naturally occurring dissolved compounds in the water, called Geosmin and Methylisoborneol (MIB) 

Human noses and tastebuds can detect Geosmin and MIB at very low concentrations. These compounds are sometimes present in drinking water, but not usually at noticeable levels. Changes in the temperature can increase some kinds of algae and bacteria naturally present in the water source (Glennies Creek Dam) that can cause a rise in Geosmin and/or MIB above the taste and odour threshold. 

 Unfortunately, Geosmin and MIB are not removed from water using routine treatment processes. However, the water is safe to drink and use for all normal purposes. Council’s water treatment processes are working normally with water quality results being consistently compliant with the Australian Drinking Water Guidelines. 

 In times when increased levels of Geosmin and MIB are present, extensive monitoring of the water quality occurs to confirm there are no health risks associated with the drinking water. Council may implement additional treatment processes, such as Powdered Activated Carbon (PAC) dosing to reduce these compounds, but it will not remove them completely.

 Geosmin is only an aesthetic concern.  We do appreciate people’s patience and understanding in these events, as we continue to do everything we can to improve the taste and odour problems in our drinking water supply.

Geosmin and MIB and the Treatment Process
Council’s uses many treatment processes to remove algae, particulates and dissolved compounds from the water sourced from Glennies Creek Dam. 

To remove Geosmin and MIB, to below detectable odour and taste levels, activated carbon can be added as a pre-treatment, which is then removed as part of the filtration process.  Activated carbon is extremely porous and absorbs taste and odour compounds onto its surface. 

However, the amount of activated carbon needed to remove the levels of Geosmin and MIB below the odour and taste detection levels in some instances exceeds the design capacity of the water treatment plant.  In the event of detectable levels of Geosmin and MIB, water quality testing is increased and all treatment options available to Council are investigated.

Is the water safe to drink?
Yes, the potable town water supplied by Singleton Council, as the Local Water Utility, is safe to drink.  Our treatment processes are designed to remove any harmful toxins, algae and other organic matter or particulates.  All potable water we supply fully complies with all health based requirements in the Australian Drinking Water Guidelines, and extensive monitoring continues to confirm there are no health risks associated with the drinking water. 

Geosmin is only an aesthetic concern.

Why can I still taste and smell it is it is being removed?
Unfortunately, Geosmin has a very strong, unpleasant taste and odour, which is harmless. Sensitive individuals may still detect the odour of Geosmin at extremely low levels, as it has a taste and odour threshold of approximately 0.00001 mg/L (10 ng/L). In comparison, the taste threshold for chlorine is generally considered to be between 0.1 and 0.4 mg/L.

When will it be fixed? 
Due to a warmer than usual winter and ongoing favourable conditions for algae growth it is not possible to predict how long the Geosmin and MIB will remain at high levels in the raw water. Once the algae level has declined, there may still be high levels of Geosmin in the water afterwards. As the weather cools, Geosmin levels typically decrease.  All treatment process options to reduce the effects of Geosmin and MIB on the drinking water supply are being investigated by Council.

Is there anything I can do to reduce the taste?
There have been reports that putting water in a jug in the fridge can help with any taste and odour issues. As well as adding lemon or fruit wedges (orange, mint, cucumber, watermelon, etc) to water to help mask the odour and taste.