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Water Authority Moves to Build $159 Million Treatment Plant

Posted on: Friday, 9 September 2005, 18:00 CDT

Sep. 9--SAN DIEGO -- Moving to plug a growing hole in San Diego County's drinking water supply, county water officials voted unanimously Thursday to spend $159 million to build a state-of-the-art treatment plant in San Marcos that will be the largest of its kind in the world.

The plant will be the first in the San Diego County Water Authority's 61-year history, and will be built -- and operated for at least the first 15 years -- by Oregon-based CH2M Hill, an engineering, construction and operating company that has worked in 110 countries.

The plant is expected to start pumping 100 million gallons of drinking water a day for county residents by April 15, 2008. In addition to the $159 million construction cost, the Water Authority will also pay CH2M Hill $6 million a year to operate the plant. Construction is to begin early next year.

Water Authority officials say county residents face drinking-water shortages if the plant is not built, because existing treatment plants are already struggling to meet "peak" demands -- and regional populations are continuing to grow.

Agency officials have warned for the past three summers that county residents could face mandatory cutbacks on the hottest summer days, but no cutbacks have materialized.

Almost all the water San Diego County residents use is imported from the Colorado River and Northern California. About half of the imported water is treated outside the county and shipped in. The other half is "raw" water that is treated by local cities and agencies that have small treatment facilities. But those plants are operating at peak capacity. The new plant will let the Water Authority take more raw water and turn it into badly needed drinking water.

Water Authority officials said the new plant will be "the latest and the greatest" in water treatment technology, using membranes instead of chemicals as the principal method of removing bacteria, viruses, sediments and other contaminants.

Conventional water treatment methods use a variety of chemical processes to clean water once larger matter is filtered out. Chemicals called "flocculents" stick to contaminants. That causes them to congeal and sink, allowing clean water to be skimmed from the top or extracted by running it through sand.

However, those systems create lots of contaminant "sludge" that must be removed from plants.

More advanced chemical systems bubble ozone gas up through water that "eats up" contaminants. But those processes are expensive.

Water Authority officials said Thursday that the Twin Oaks plant will suck raw water through banks of membranes -- similar to highly advanced coffee filters -- to remove nearly all bacteria, viruses and other contaminants. Then, it will bubble ozone up through the filtered water, and finally pass it through carbon filters.

Project manager Tim Suydam said the system creates extremely clean water, because the membranes' filtering pores are so tiny.

"We're down to the point-one micron (one-thousandth of a millimeter) level," he said, "tiny enough to take out chryptosporidium, giardia, viruses."

Suydam said operating the plant would also be cheaper than straight-ozonization plants because pre-filtering the water with membranes will reduce the amount of ozone the plants needs.

The Olivenhain water district in Encinitas has operated a smaller, membrane-treatment plant for the last couple of years. That plant does not include the ozone and carbon-filter systems that the Water Authority's plant will.

Greg Quist, the Water Authority board member from Escondido's Rincon del Diablo Water District, said the Olivenhain plant was the most impressive he'd seen.

"I've actually tested the water at Olivenhain, and that's the cleanest water I've ever seen before," he said. "So I'm a big fan of membrane technology."

Thursday's discussion was not completely without controversy, however.

Board member Fred Thompson of the city of San Diego, said he was concerned by a court battle among competing companies over the patent rights to the membranes that the new plant would use -- and wondered if the legal battle could leave the plant without the membranes that it needs.

Suydam and Water Authority attorneys said they did not think any legal ruling would force companies to stop making the membranes, but to pay royalties to the patent holders.

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Copyright (c) 2005, North County Times, Escondido, Calif.

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Source: North County Times

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