Have you ever smelled the air after it's rained on dry soil, or caught scent of a freshly ploughed field? How does that smell get into our water?
Geosmin is a harmless, naturally occurring compound produced by bacteria in soil and algae found in surface water (lakes, rivers, streams, dams). Geosmin produces an earthy, musty-type odour/taste, like that of overturned rich soils, and is present in foods such as beets, spinach, and mushrooms. 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.
The first indication of geosmin in the Pockwock water supply occurred in fall 2012. The Pockwock water supply serves customers in Halifax, Bedford, Sackville, Fall River, Waverley, and Timberlea. Geosmin hasn’t been detected at Pockwock over the last two years but has recently been found at a level some customers can notice. A list of geosmin concentrations in the treated water dating back to January 2017 can be found on this page.
Frequently Asked Questions
Recent changes in source water quality, through natural processes, including increased pH and organic carbon, combined with warm summer temperatures can promote algal growth, which can lead to the production of geosmin.
Some customers are reporting 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.
While the taste and odour can be unpleasant, geosmin is not harmful. The water remains safe to drink. On-going testing continues to show an absence of harmful bacteria and other pathogens in the water.
It is not possible 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. It is expected the concentration of geosmin will fluctuate during the coming weeks/months, however, we are not able to predict the duration based on historical trends.
A list of geosmin concentrations in the treated water dating back to January 2017 can be found on this page.
Geosmin was most recently detected on October 28, 2019 at a concentration of 12 ng/l in the treated water. To put this into context, the general threshold for human detection is about 15 nanograms per litre (15 nanograms per litre = 15 parts per trillion). However some people 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.
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. 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.
Chilling the water, adding ice cubes, a slice of lemon, or a few drops of lemon juice can help reduce the odour and taste produced by geosmin.
Halifax Water has engaged a private, third party accredited laboratory to provide on-going testing for geosmin and 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.
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.
With the source water changes that we have been seeing over the past few years, including increased algal activity, Halifax Water is developing a long-term capital plan that will ensure the treatment process is able to continue to provide high quality, safe drinking water, while also being robust enough to adapt to future source water conditions, including the presence of geosmin. Halifax Water has been working with both consultants and researchers at Dalhousie University, through work at both the bench and pilot scale to study potential treatment options that will be incorporated into the long-term capital plan.
The implementation of a multi-million dollar engineered solution could take several years and involve continued research, pre-design, detailed design, regulatory approval, and construction activities.
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. The health and safety of customers will be foremost.
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.
Testing & Results
Testing of geosmin at the Pockwock Water Supply Plant began in October of 2012 and has been on-going ever since. Testing takes place twice per month . The general threshold for human detection is about 15 ng/L (15 nanograms per litre = 15 parts per trillion). However, some people with sensitive palates can detect these compounds in drinking water when the concentration is as low as 5 ng/L.
Recent Geosmin Concentrations (ng/L)
|Sample Collection Date||Treated Water Concentration (ng/L)|
|November 25, 2019||14|
|November 12, 2019||12|
|October 28, 2019||12|
|September 16, 2019||Non-Detect|
|August 08, 2019||Non-Detect|
|July 18, 2019||Non-Detect|
|June 05, 2019||Non-Detect|
|May 01, 2019||Non-Detect|
|April 15, 2019||Non-Detect|
|March 05, 2019||Non-Detect|
|February 11, 2019||Non-Detect|
|January 16, 2019||Non-Detect|
|December 18, 2018||Non-Detect|
|December 11, 2018||Non-Detect|
|December 05, 2018||Non-Detect|
|November 20, 2018||Non-Detect|
|November 14, 2018||Non-Detect|
|November 06, 2018||Non-Detect|
|October 29, 2018||Non-Detect|
|October 22, 2018||Non-Detect|
|October 15, 2018||Non-Detect|
|October 09, 2018||Non-Detect|
|October 01, 2018||Non-Detect|
|September 24, 2018||Non-Detect|
|September 13, 2018||Non-Detect|
|August 23, 2018||Non-Detect|
|August 13, 2018||Non-Detect|
|July 25, 2018||Non-Detect|
|July 19, 2018||Non-Detect|
|July 05, 2018||Non-Detect|
|June 05, 2018||Non-Detect|
|May 07, 2018||Non-Detect|
|April 09, 2018||Non-Detect|
|March 05, 2018||Non-Detect|
|February 12, 2018||Non-Detect|
|January 08, 2018||Non-Detect|
|December 14, 2017||Non-Detect|
|November 27, 2017||Non-Detect|
|November 15, 2017||Non-Detect|
|October 30, 2017||Non-Detect|
|October 19, 2017||5|
|October 05, 2017||6|
|September 20, 2017||10|
|September 06, 2017||12|
|August 23, 2017||9|
|August 08, 2017||4|
|July 24, 2017||Non-Detect|
|July 14, 2017||Non-Detect|
|June 27, 2017||Non-Detect|
|May 30, 2017||Non-Detect|
|May 15, 2017||Non-Detect|
|May 03, 2017||Non-Detect|
|April 18, 2017||3|
|April 04, 2017||4|
|March 20, 2017||4|
|March 10, 2017||4|
|February 23, 2017||5|
|February 07, 2017||5|
|January 23, 2017||6|
|January 12, 2017||6|