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 naturally occurring compound produced by bacteria in soil and algae in surface water (lakes, rivers, streams, and dams). Geosmin produces the odour of rich overturned soils, or an earthy smell. 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. You will smell geosmin more when you are in the shower as heating the water increases the volatility of its compounds.
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.
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, including:
- On-going research with Dalhousie University to evaluate treatment strategies to reduce geosmin and other taste and odour compounds in drinking water
- Halifax Water hired an environmental consulting firm who completed several study to better understand the occurrence and cause of geosmin in Pockwock Lake.
- Halifax Water hired an engineering consulting firm to review treatment options and associated costs to reduce geosmin. The options brought forward by this consulting firm are currently being evaluated
- Continuous testing of geosmin levels at various strategic locations throughout the Pockwock watershed
- On-going consultation with water utility experts throughout North America.
Why Do We Suddenly Have Geosmin?
Lake recovery is the phenomenon whereby the reduction of acid rain in Nova Scotia has enabled the pH levels in local water sources to rise from a level that didn't accommodate much biological activity, to a level that is very conductive to organic life. This shift in the pH level of local water sources is encouraging biological activity in our water sources, and while this is, of course, a very positive effect environmentally in both the United States and Canada, it brings with is a host of challenges in the treatment of these water sources for consumption. This increased level of organic life in Pockwock Lake was not present or planned for during the design of the J.D. Kline Water Supply Plant in the previous century.
The J.D. Kline Water Supply Plant serves Halifax, Bedford, Sackville, Fall River, Waverley, Timberlea, Spryfield, and Herring Cove. Pockwock Lake, which is the water supply for the J.D. Kline Water Supply Plant, is experiencing lake recovery.
In Pockwock Lake, this recovery is causing some customers to notice a fishy or musty/earthy taste and odour which is caused by geosmin. This change in taste and odour is not a human health concern, and testing of the treated water shows the water remains safe to drink.
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)|
|December 20, 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|