Skyland water goes high-tech
Faced with a common problem, Tahoe Basin water suppliers have followed different paths in guaranteeing the quality of the drinking water they draw from Lake Tahoe.
While several other suppliers around the lake have built plants to disinfect the water with ozone, the Skyland General Improvement District has become the second district in the basin to build a filtration plant to remove all microorganisms from the water supply.
But, unlike the Round Hill General Improvement District, which opened a sand-filtration plant last summer, the Skyland district has opened a high-tech microfiltration plant that relies on spaghetti-like plastic filters.
Still in the shakedown process after three months of operation, the $4.9 million plant provides about 750,000 gallons of filtered water a day to 1,200 East Shore customers. Among those receiving water from the new plant are residents of Cave Rock, Hidden Woods, LakeRidge and Logan Creek.
“It’s a high-tech system that’s state of the art,” said Chris Mozley, a Douglas County plant operator who helps run the system for the district. “There’s nothing else like it at Lake Tahoe. I feel fortunate to be a part of its construction and operation.”
The secret to the microfiltration plant is an array of 90 filter units, each a 4-foot-long canister that holds a bundle of 19,000 spaghetti-like strands, called lumen, made of polypropylene. The surface openings on the strings are just a fifth of one millionth of an inch, small enough to filter out such disease-causing micro-critters as giardia and cryptosporidium. The two organisms have been responsible for outbreaks of illnesses in various areas of the United States, including a 1992 cluster of giardiasis – a nagging, but non-fatal intestinal disorder – at Lake Tahoe.
Unlike a reverse-osmosis filtering system, which relies on pressures of 200 to 400 pounds per square inch, the Skyland micro-filtration plant uses just 13.8 pounds of pressure to force the lake water through the array of 90 filters. The lower pressure minimizes the types of problems that can occur.
Joseph D. Rufo, the chairman of the Skyland board of trustees, said the district settled on the Australian-built filtration plant after a methodical evaluation of the water it draws from Lake Tahoe. Participating in the research were the Battele Institute of Ohio State University, Lawrence Livermore and the University of Southern Florida.
“The data acquired by me from academia revealed that the ozone concept did not give us full protection relative to giardia and cryptosporidium,” said Rufo, a former associate engineer in the U.S. Navy’s research laboratories. “Ozonation was only acceptable if used in conjunction with chlorine, and that was unacceptable to us here in Skyland.”
The district pumps Lake Tahoe water from a depth of 70 feet 1,700 feet off shore.
While Skyland still injects chlorine into its treated water, the low concentration – half a part per million parts of water – does not detract from the taste and odor of the filtered water. And the filtration system reduces the water’s turbidity by 90 percent, Mozley said.
It’s the plant’s filtering system that Mozley said makes Skyland water better than ozone-treated drinking water.
“Ozone kills everything in the water, but leaves it in the water,” Mozley said. “Filtration removes everything.”
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