Department of Water Resources
A daily compilation of significant news articles and comment
March 21, 2008
4. Water Quality
Palmdale Water District working to improve disinfection process
By Alisha Semchuck, staff writer
PALMDALE - Palmdale Water District customers can look forward to better-tasting, odorless water in late fall after the agency completes disinfection improvements.
Construction is in the works for eight concrete basins, or contactors, at the district's water treatment plant on Avenue S, just west of
The carbon adds one more step to the purification of tap water. District board members voted 5-0 last week for approval of a $1.53 million contract to cover the initial shipment of enough carbon for seven contactors. That price includes installation, startup and testing.
Matt Knudson, the district's engineering manager, told the board the district received two bids, one from Calgon Carbon Corp. in
"Staff recommends awarding a contract to Calgon," Knudson said. "They were quite a bit less." Norit wanted nearly $1.76 million for the same product and services, which would have cost $228,533 more.
Contactors containing granular activated carbon "act as secondary filters," Knudson said. The carbon removes contaminants. "Once the absorptive capacity is exhausted," after roughly six months, the carbon should be replaced, he said.
Replacement costs also were less expensive through Calgon, which quoted a $252,143 per contactor unit for 2008 and $272,314 for 2009. Norit asked $331,239 and $357,737 for those same years.
One possible hitch with Calgon: It sent the district a letter stating it couldn't guarantee replacement costs beyond 2009 because the "production of activated carbon is very closely tied to the energy markets, and the volatility of these markets makes it impossible for us to predict with any degree of accuracy what our costs might be beyond 2009."
Knudson said the district wasn't too concerned about a potentially huge hike in granular activated carbon replacement costs in 2010 or 2011. He pointed out that the district isn't "locked in" with Calgon indefinitely - the contract stipulates initial supply and replacements for this year and 2009. Because the product won't be delivered until later in the year, Knudson didn't anticipate any replacements in 2008.
If Calgon's price for 2010 or beyond is too high, Knudson said the district could go back out to bid or work with Calgon "to tie future prices to the Producer Price Index."
By using the carbon, the water district can continue using chlorine as a disinfectant rather than switching to chloramines and still be in compliance with Environmental Protection Agency standards to reduce the levels of trihalomethanes in drinking water, Knudson said. Trihalomethanes are by-products resulting when chlorine interacts with natural organic material, such as decaying plants, in the surface water the district takes from the California Aqueduct.
The EPA mandated reduction of the trihalomethanes, which have been linked to a higher rate of certain health risks such as bladder, rectal or colon cancer, although the EPA Web site said those findings are not conclusive.
Dluzak described the carbon as "one of the best technologies" for removing contaminants such as herbicides and benzene.
The carbon also removes pharmaceuticals, Knudson said.
Dluzak called the use of carbon "a paradigm shift. Most agencies strive to meet the state standards" for lowering trihalomethanes. "PWD wants to provide the best quality water. When you go to chloramines, you're adding another chemical. We're trying to remove chemicals." #
http://www.avpress.com/n/18/0318_s14.hts
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