Water Quality

Posted 04/28/10, by Skagit PUD | 0 Comment(s)

T his spring, Skagit PUD has experienced an increase in the number of customer calls involving taste and odor concerns. Taste and odor issues are some of the most difficult for a water system to address.

One reason for the difficulty is that taste and odor evaluations are very subjective: what is offensive to one individual may not be even detectable to another.

All water has its own unique taste and odor characteristics. Skagit PUD’s water treatment plant draws water from Judy Reservoir, east of Clear Lake, which is supplied from four streams within the Cultus Mountains and the Skagit River. Like many other water systems, we occasionally experience taste and odor changes. The types of odors in drinking water are directly related to the compounds present in the source water.

Algae Growth

The most significant source of odor in water supplies is the growth and decay of microorganisms in surface water. Blue-green algae, green algae, diatoms, and flagellates are the four algae groups responsible for most odor complaints. Algae thrive at different times of the year in reservoirs. As these organisms grow and multiply, they excrete small amounts of harmless chemicals into the water that cause a musty, moldy, or earthy taste and odor. Although algae are removed during the treatment process, some of their metabolites (non-toxic, odorant chemicals) may be left behind.

Concentration Levels

The two most common metabolites are geosmin and 2-methylisoborneal (MIB). Even though these compounds are harmless, the human senses of taste and smell are extremely sensitive to them and can detect them in the water at concentrations as low as five parts per trillion.

Algae are common, normal inhabitants of surface waters and are beneficial to the health of a water body. Low concentrations of most algae are an asset rather than a liability in a raw water source. Algae are important as primary producers of organic matter at the base of the food chain and are useful indicators of pollution. They help remove excess nutrients, produce oxygen and provide spawning habitat for fish.

Fortunately, for PUD customers, these earthy or musty odor events are temporary in nature, usually disappearing entirely when the temperature of Judy Reservoir changes.

The by-product that causes the odor is not harmful, nor will it affect normal water usage.

Please feel free to contact Skagit PUD if you have questions about the quality of your water.

Taste & Odor Tips

1. Flush your faucet for several minutes.
2. Collect freshened water into a clean container suitable for beverages, cover or cap it, and store it in the refrigerator for future drinking and cooking purposes.
3. Adding one or two teaspoons of lemon juice or a slice of lemon to refrigerated drinking water can also help improve the taste.
4. If the taste and odor is still present, you may want to consider an NSF certified home water treatment device.