Odors Originating from the Source Water
Occasionally, odors that customers detect in their water originate with the source water and pass through the treatment process. This infrequent issue is more likely to happen with water originating from the City of Fairfax water treatment plant, which generally serves our customers in Ashburn Farm, the Belmonts, Broadlands, Villages of Waxpool and the Landfill Water Service Area. If this happens, it will be a widespread problem. Several customers will call, indicating their water smells “musty” or “like a pond.” The most frequent cause for this is when the City of Fairfax begins supplementing Goose Creek with water from the Beaver Dam reservoir and chemical dosage has not been properly changed to address the different source characteristics.
Causes of Source Water Odors
- Algae and algal blooms – earthy, musty moldy odors
- Decaying organic matter such as leaves, aquatic plants, or algae – swampy, grassy, woody, or septic odors
- Fungi – earthy or musty odors
Most Common Times for Occurrence:
- During a long dry spell, when the City of Fairfax starts withdrawing from Beaverdam Reservoir
- Mid- to late-summer, when algal blooms occur
- Late-summer, when the reservoir temperature gets very warm, enhancing biological activity decaying the organic matter
- Mid-fall, when the water in the reservoir “turns over,” potentially stirring up the decayed matter that rests on the bottom
Water treatment plants remove most tastes and odors through coagulation and flocculation (i.e., settling out the particulates, see EPA's Water On Tap: What You Need to Know that describes the water treatment process www.epa.gov/safewater/wot/index.html. However, the City of Fairfax also adds powdered activated carbon (PAC) to their treatment process to remove additional tastes and odors. Treatment chemicals are added in regular quantities, depending upon the flow passing through the plant. When the concentration of taste or odor causing material changes in the raw water, amount of chemicals the plant adds will need to change. If the plant does not know about the changing concentration of taste and odor causing materials in the source water, tastes and odors can get into the water our customers drink prior to the chemical concentrations being modified to compensate for the change.
Is there a health risk?
In general, odors caused from these naturally occurring organic compounds do not pose health risks.
Other odors such as stale smells from a lack of use in certain parts of the distribution system indicates a loss of disinfectant residual and has the potential to pose a health risk.
Bad tastes or odors that come from cross-connections are a health risk.
What to do:
If you notice an odor similar to the information above, contact Loudoun Water's customer service department, 571.291.7700.