Understanding Geosmin in Our Drinking Water
From time to time, some residents may notice an earthy or musty taste or smell in their drinking water. This comes from a natural compound called geosmin. While the taste and odor can be unpleasant, geosmin is not harmful and the water remains safe to drink. Ongoing testing confirms there are no harmful bacteria or other pathogens in the water. This is a normal, natural issue that communities across Canada and around the world sometimes experience — most often when the weather is warm at the end of summer.
Quick Answers (FAQ)
- Is my water safe? Yes. Geosmin affects taste and smell, not safety. Routine testing shows no harmful bacteria or pathogens.
- What causes it? Naturally occurring geosmin from algae and bacteria in surface water (lakes, rivers, streams). It is not pollution and not a treatment failure.
- When does it happen? Infrequently, and most often in late summer into early fall when water is warm.
- How can I reduce the taste/odor at home? Chill the water, add lemon, or use a carbon filter; also check whether odors may be from the sink drain.
What Is Geosmin?
Geosmin is a harmless, naturally occurring compound produced by certain algae and soil bacteria found in surface waters. It smells earthy or musty, similar to rich soil after rain. It is not the result of pollution or a failure of the treatment process.
Why Can We Smell It So Easily?
The human nose is extremely sensitive to geosmin —even tiny amounts can be noticed. Heating water can make the smell more obvious, which is why it is sometimes stronger in showers or hot drinks.
When and How Often Does It Occur?
Geosmin events are influenced by natural changes in source water quality (such as pH and organic carbon) combined with warm temperatures that promote algal growth. While timing can’t be predicted precisely, it typically occurs late summer into early fall and then subsides as conditions change.
What You Can Try at Home
- Chill your water or add ice.
- Add a slice of lemon or a few drops of lemon juice.
- Use a carbon filter designed for drinking water.
Tip: Sometimes odors come from sink drains rather than the water. To check, fill a clean glass with cool water and step away from the sink before smelling. If the glass does not smell, clean the drain (for example, a small amount of bleach in the trap).
Monitoring and Current Levels
The City of Bathurst has monitored geosmin since 2017. Levels vary from year to year with weather and source-water conditions. As an example, in June 2024, geosmin levels measured about 10 nanograms per liter (ng/L); many people only begin to notice geosmin around 15 ng/L, though sensitivity varies by person. All testing is performed by an independent, accredited laboratory, and routine water quality tests continue to show the absence of harmful bacteria and other pathogens.
Treatment and Long-Term Planning
Standard drinking water treatment cannot fully remove geosmin. Proven technologies—such as granular or powdered activated carbon, ozone or advanced oxidation processes, and biofiltration—can reduce it. The City is developing a long-term capital plan, working with consultants and suppliers to study upgrades that will keep water safe and high quality while addressing natural conditions like geosmin. Implementation of any engineered solution involves research, design, approvals, and construction, and may take several years.
Bottom Line
Geosmin is a natural and uncommon occurrence that can affect taste and smell—especially toward the end of summer. It does not affect safety. We will continue monitoring closely and keep residents informed.