New Algae Species Complicates District's Efforts to Improve Taste, Smell of Drinking Water

Water quality experts are dealing with an unrelenting new strain of algae in Lake Skinner that is affecting the taste and smell of drinking water being served to consumers in San Diego and southwest Riverside counties.

The Metropolitan Water District of Southern California (MWD) has applied four treatments of copper sulfate since Aug. 8 to address the growth of a persistent new species of blue-green algae in the drinking water reservoir near Temecula.

"We're hoping that we've turned the corner in dealing with this aggressive new algae strain, which has been particularly difficult to treat," said Jill T. Wicke, MWD's manager of water system operations. "Since the last treatment Sept. 17, we have observed a decline in algae in the lake, which we expect will continue to decline with Saturday's application.

"We also expect that cooler fall temperatures will help reduce algae growth and re-growth. It might, however, take as long as three weeks before some consumers notice an improvement in the taste and smell of their drinking water," Wicke said on Sept. 23.

Wicke reiterated that water with an earthy-musty taste and smell continues to be safe to drink, but that consumers with sensitive noses and palates may find it unpleasant. The earthy-tasting water -- which cannot be corrected in the filtration and treatment processes -- is being supplied by Metropolitan to supplement local supplies of Eastern and Western municipal water districts, based in Perris and Riverside, respectively, and the San Diego County Water Authority.

While the Sept. 24 copper sulfate treatment takes effect, Metropolitan continues to by-pass the lake through nearby pipelines to isolate the lake's supplies in its distribution system. Metropolitan ultimately plans to return the lake to service once the water's aesthetics improve.

In the meantime, consumers noticing an earthy-musty taste and smell in their drinking water can refrigerate it to improve its aesthetics or should consider using bottled water, officials said.

Growth of algae in open reservoirs is generally a seasonal problem that usually occurs in warm months. As in previous years, the cause of this year's taste-and-smell episode has been identified as 2-methylisoborneol (MIB) and geosmin, compounds that are produced from the growth of certain algae in freshwaters throughout the world. Typically, MIB and geosmin levels increase in summer months when the warmer weather accelerates algae growth.

This year, however, the seasonal issue has been complicated by the appearance of the new algae species, Planktothrix perornata, which was first identified in Lake Skinner in late August, said Dr. Mic Stewart, Metropolitan's water quality manager.

"Unlike other freshwater algae species, which attach to the sides or bottom of a reservoir, this new strain tends to proliferate throughout different lake levels, making it much more difficult to treat because of its widespread occurrence in the lake," Stewart said.

Metropolitan officials speculated that the new algae species might have been imported in supplies from Northern California following the June 2004 levee break in the Upper Jones Tract island of the San Francisco Bay/Sacramento-San Joaquin Delta. Dr. Stewart noted that recent reports suggest the new species has caused similar problems in the northern part of the State Water Project.

Consumers interested in receiving additional information about the quality of Metropolitan's drinking water supplies may visit MWD's Web site,, for the district's annual water quality report and other related materials.

This article originally appeared in the 09/01/2005 issue of Environmental Protection.

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