Gilroy
– A Las Vegas-area chemical company with past perchlorate
pollution switched in May from ion exchange – the groundwater
treatment method being used in Morgan Hill and San Martin – to
single-cell bacteria that eat the chemical.
Gilroy – A Las Vegas-area chemical company with past perchlorate pollution switched in May from ion exchange – the groundwater treatment method being used in Morgan Hill and San Martin – to single-cell bacteria that eat the chemical.
Officials here hope the Olin Corporation can learn something from this method, but Olin cleanup consultant Evan Cox says the company is well aware of these perchlorate-eating germs and is already using them to break down perchlorate in the soil at its former road flare factory site in Morgan Hill. They are “nothing new,” said Cox, of the GeoSyntec consulting firm in southern Ontario. “Olin is aware of all the technologies that are available.”
Morgan Hill Mayor Dennis Kennedy said he knows about germs being used to treat the Olin site, but he still thought the Nevada development was “intriguing, and something we should follow.”
Active San Martin resident Sylvia Hamilton said, “It certainly is positive that some company has found something that they think would be more expedient than ion exchange.”
The Kerr-McGee Corporation, which dumped the perchlorate in Henderson, Nev., is finding that the bacteria remove slightly more perchlorate than an ion exchange system, according to Environmental Affairs Director Pat Corbett.
“The ion exchange was about 99-percent effective in the removal of perchlorate,” Corbett said. “The biological method is probably about 99.99.”
The two technologies cost about the same to install, he said, but Kerr-McGee doesn’t yet know how much the new one will cost to maintain.
“It’s a living system,” Corbett said. “The care and feeding is a bit more difficult. … (The bacteria) like consistency in their feed. … They like relatively consistent pH control and temperature.”
Kerr-McGee used an ion exchange treatment plant from 1999 until this May. They switched because “technical problems” with the system were preventing them from meeting a treatment deadline, Corbett said.
The bacteria also do a very good job of eating nitrates, plentiful in south Santa Clara Valley groundwater. In fact, the bacteria eat nitrates before perchlorate, so with more nitrates, Olin might need more bacteria per gallon than Kerr-McGee.
“The technology of choice is going to be very much dependent on the water you’re dealing with,” Corbett said. “We have one type of water in Henderson, and you may have something completely different at your location.”
Bacteria have been used for many years to break down spilled pollutants and were one of the early options available when perchlorate was discovered nationally in the late 1990s, Corbett said. Bacteria and ion exchange were the two leading cleanup methods in 1997, when Kerr-McGee officials first found out about their three-mile perchlorate plume that had seeped into the Las Vegas Wash – and from there into Lake Mead and on down the Colorado River.
The city of Las Vegas gets its water from Lake Mead, and Colorado River water is a major source of farm irrigation in Southern California. Perchlorate has been found in supermarket lettuce and cows’ milk in California.
Now, Kerr-McGee has contracted with the Veolia Water firm to build a quarter-acre water treatment plant on the site of its still-operational chemical factory. They have grown colonies of bacteria inside the plant’s tanks, and groundwater from three different wells filters twice through these tanks before being pumped into Lake Mead.
Veolia owns the process and closely guards all information about the bacteria, including its name. Nevertheless, Cox says a University of California-Berkeley scientist has identified at least two dozen varieties of bacteria that eat perchlorate.
Olin doesn’t import bacteria for its Morgan Hill site like Kerr-McGee does. It rather adds a chemical to the soil that increases the population of existing bacteria, which are more than capable of doing the job.
Perchlorate from Olin’s Morgan Hill plant has spread through groundwater in a plume of at least eight miles southward and somewhat northward.
Olin is currently using ion exchange treatment plants on the wellheads of San Martin’s two private water companies and on Morgan Hill’s Nordstrom well. The state’s Central Coast Regional Water Quality Control Board recently gave the city of Morgan Hill permission to turn on an ion exchange treatment facility at the Tennant well, across the street from the Olin site.
It appears to be working well, said David Athey, of the Central Coast Regional Water Quality Control Review Board. The water is entering these ion exchange filters with 29 parts per billion of perchlorate and exiting with fewer than 4 ppb, Athey said.
Cox declined to answer questions about whether Olin could or should consider switching from ion exchange to bacteria for groundwater. Olin officials did not return phone calls as of press time.
“Since perchlorate is somewhat of an emerging issue, … the solutions to the problem are in development, so it’s necessary to network about them,” said hyrdogeologist Tom Mohr, the Santa Clara Valley Water District’s perchlorate project manager.
