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HRWC

Geosmin

Frequently Asked Questions

* Updated October 8, 2013

 

What is causing the taste and odour experienced by some customers served by the Pockwock water supply?

Recent test results, dated September 27, 2013, from a private, third party accredited laboratory, confirm the presence of geosmin, a naturally occurring compound found in surface waters (ie. lakes, rivers, stream, dams).

 

What is geosmin?

Geosmin is a naturally occurring compound produced by bacteria in soil and algae found in surface water. Geosmin produces the odour of overturned rich soils and is present in foods such as beets, spinach, and mushrooms.

 

Why does it occur?

Since the first indication of geosmin in the Pockwock water supply in fall 2012, Halifax Water has taken a number of steps to better understand geosmin. These steps include; on-going research at our Pockwock Pilot Plant (a research facility located at the Pockwock water supply plant) in conjunction with Dalhousie University, to evaluate treatment strategies to reduce geosmin and other taste and odour compounds in drinking water; funding allocated to study treatment options to reduce geosmin; continuous testing of geosmin levels at various strategic locations throughout the Pockwock watershed; and on-going consultation with water utility experts throughout North America. 

Geosmin is NOT the result of pollution or contamination of our source waters, and is not a result of a failure of treatment processes. It occurs through a natural process.

 

Where is the odour and taste occurring?

There are reports of an earthy, musty-type odour/taste in the water coming from a variety of areas served by the Pockwock water supply. Pockwock serves customers in Halifax, Bedford, Sackville, Fall River, Waverley, and Timberlea.

 

Is the water quality affected?

While the taste and odour can be unpleasant, geosmin is not toxic or harmful. The water remains safe to drink. On-going testing continues to show an absence of harmful bacteria and other pathogens in the water.

 

How long will the taste and odour last?

It is impossible to predict the onset of an incidence of geosmin, or how long it will last. Geosmin compounds have been shown to remain in lakes and reservoirs for days to months.

Halifax Water began testing the Pockwock water supply in October 2012 to determine the possible source of the taste and odour experienced by some customers. It was confirmed that geosmin was the source. Testing has continued since that point with levels fluctuating on a weekly basis. Since May 2013, geosmin levels have remained consistently below detection levels. Test results dated September 27, 2013 indicate geosmin is present in the treated water from Pockwock Lake at a concentration of 8 nanograms per liter (8ng/L). To put this into context, the general threshold for human detection is about 15 nanograms per liter(15 nanograms per litre = 15 parts per trillion). However people with sensitive palets can detect geosmin in drinking water at concentrations as low as 5 nanograms per liter. This explains why some residents notice the taste and odour, while others do not.

 

Can the taste and odour be reduced at the tap? 

To make the water taste better, try chilling it, adding ice cubes, a slice of lemon, or a few drops of lemon juice.

 

What does it smell like?
Geosmin typically produces an earthy or musty odour as is found in the odour of overturned rich soils, and is present in some foods such as beets, spinach, and mushrooms.  


Why do we smell it?

The human nose is extremely sensitive to geosmin. If you poured a teaspoon of geosmin into the equivalent of 200 Olympic-sized swimming pools, you would still be able to smell it.

The general threshold for human detection is about 15 ng/l (15 nanograms per litre = 15 parts per trillion). However people with sensitive palets can detect these compounds in drinking water when the concentration is as low as 5 ng/l.

Heating the water increases the volatility of these compounds, which explains why the smell is more easily detected when you are in the shower or when used for hot beverages.


How does Halifax Water detect it?

Prior to fall 2012 Halifax Water had never experienced geosmin in the water supply, so had not routinely tested for this naturally occurring compound. Halifax Water has engaged a private, third party accredited laboratory to provide on-going testing for geosmin.

Halifax Water continues to follow a rigourous protocol of regular monitoring of both the raw and treated waters across all of our source waters. On-going testing continues to show an absence of harmful bacteria and other pathogens in the water. The water remains safe to drink.



What is the geosmin concentration in Pockwock Lake?

Water samples continue to be collected weekly from the Pockwock Water Treatment Plant for geosmin analysis. Results from the monitoring program can be found at Geosmin Test Results .

 

Can it be removed from the drinking water?
Geosmin is not removed by conventional water treatment processes used by Halifax Water at the Pockwock water treatment facility.

There are several proven treatment technologies for removing geosmin from drinking water including granular or powdered activated carbon; oxidation with ozone or advanced oxidation processes (AOPs); biofiltration; or some combination of each. The actual technology used at a specific plant is highly dependent on the chemistry of the source water.

Halifax Water has allocated funds to study treatment options to reduce geosmin. Any engineered treatment solution must first be evaluated to ensure the installation of a system to treat geosmin does not negatively impact the current treatment processes.

The implementation of a multi-million dollar engineered solution could take 2-3 years and involve continued research, pre-design, detailed design, regulatory approval, and construction activities.

In conjunction with on-going water research being undertaken at our Pilot Plant Facility at the Pockwock Water Treatment Plant, Halifax Water is conducting research into biofiltration, advanced oxidation processes (AOPs) and granular activated carbon and their potential to control taste and odour related to geosmin. 

 

Will Halifax Water be investing in treatment processes to remove geosmin?

Halifax Water will consult with regulatory authorities and review its ongoing research efforts to identify future infrastructure investments to improve water quality including taste and odour control. As always, the health and safety of customers will be foremost.

 

Does geosmin occur elsewhere?
Geosmin is common in many jurisdictions across Canada, the United States, and elsewhere in the world. Halifax Water’s first experience with geosmin in the local water supply occurred in the fall of 2012.