It’s in the water…but filtering is on the way

A snapshot of the last few years...data courtesy of the Town of Friday Harbor.

You know those long, scientific-sounding messages we who live in Town get from the Town of Friday Harbor about how our drinking water is doing….I’d like to report a bit of good news from the last one.

For the past few years, the levels of THM (Trihalomethane – here’s an explanation & here’s a bit more about the dangers) has hovered near the “safe” levels, and at times, exceeded them (see chart).

Now, the Town is moving ahead with plans to filter the water from Trout Lake the same way many Town residents do at home – with a filter very similar to a Brita filter, which they call a granular activated carbon contact system. This is exciting – according to Town officials, this should make our water safer and better tasting. Here’s the complete report, from the Town of Friday Harbor:

Friday Harbor Drinking Water System Users
Trihalomethane (THM) Update
April 2010 through June 2010
The Town is required to monitor your drinking water for specific contaminants on a regular basis, including the presence of Trihalomethanes (THMs), a byproduct of disinfection process. Friday Harbor water system users have the right to know about the quality of their drinking water. We have included information below that you should be aware of and what the Town is doing to correct the situation.

What are Trihalomethanes?
The problem we are experiencing continues to be the result of using Chlorine as a disinfectant for our water. Chlorination has made the U. S. water supply safe from illness and disinfection has almost completely eliminated risks of deadly waterborne diseases. However, when chlorine has long-term contact with any organic material, such as leaf foliage present in the Trout Lake reservoir or growth in the aged water distribution mains, it produces a byproduct known as Trihalomethanes (THMs). The THMs produced may have adverse health effects at high concentrations, and the federal government has set limits on the amount permissible in drinking water.

How are Trihalomethanes calculated?
THM levels are measured on a quarterly basis to calculate a “12-month” average. The State requires that we notify you if the level of THMs in the water exceeds 80 micrograms per liter (ug/L) or 80 parts per billion in said time period. Town recently measured a THM level of 83.7 ug/L, which equates to an average of 81.98 ug/L for the past twelve months.

What can you do in the home to reduce THMs?
You may wish to filter your drinking water by using activated carbon filters or simply leave your tap water standing in a pitcher in the refrigerator overnight. These simple methods will help lower THM levels.

What is the Town doing to alleviate the problem?
Filtration systems that use carbon adsorption are the most effective technology for our situation. Activated carbon filters remove and reduce many organic compounds, pesticides and herbicides, as well as chlorine, and THM compounds. As water comes in contact with the carbon, organic particles are adsorbed to the surface area of the carbon granules.

The Town Council recently authorized Town water system engineers to develop plans and specifications for a granular activated carbon contact system at the Water Treatment Plant. The concept would be akin to that of the filter at your home except at an industrial level. The Department of Health has allowed the Town to bypass the pilot testing of this system based on data and successfulness of the granular activated carbon contact system installed at the Roche Harbor Water Treatment Plant. In addition to control of THMs, Town anticipates overall improvement of the taste and odor of our drinking water quality.

If you have any questions regarding water quality related issues, please contact us at (360) 378-2810.

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