Sulfur or rotten egg odours are most commonly caused by hydrogen sulfide (H₂S), a gas that may occur naturally in oxygen-poor groundwater and wells. The smell can often be detected at very low concentrations and is considered unpleasant even when levels are relatively low. The issue is common in private wells, particularly where groundwater contains limited dissolved oxygen.
When hydrogen sulfide comes into contact with air or oxidants such as ozone, it can be converted into other sulfur compounds that can subsequently be removed through filtration. For this reason, aeration, degassing, ozone and activated carbon are commonly used to treat these odour problems.
Common Causes
- Hydrogen Sulfide (H₂S) in Groundwater
- Low Oxygen Wells
- Decomposition of Organic Matter
- Microbiological Activity
- Long Retention Time in Tanks or Systems
Common Symptoms
- Rotten Egg Odour
- Odour from Hot Water
- Odour When Water Is Drawn
- Odour After Long Stagnation
- Deposits or Discolouration in Some Cases
Common Treatment Methods
- Water Analysis
- Aeration and Degassing
- Ozone
- Activated Carbon
- Filtration After Oxidation
- UV Disinfection as Final Barrier
Example Treatment Trains
Well Water
↓
Aeration and Degassing
↓
Activated Carbon
↓
UV Disinfection
↓
Drinking Water
Well Water
↓
Ozone
↓
Activated Carbon
↓
UV Disinfection
↓
Drinking Water
Rotten egg odours are most commonly caused by hydrogen sulfide, but similar odour issues may also originate from other compounds or microbiological activity. Since the root cause affects the treatment approach, both water analysis and consultation with a qualified water treatment specialist are generally recommended before selecting a treatment solution.