It is a tiny bug, but cryptosporidium can be deadly.
And although it has never caused an outbreak of illness in Ventura County, the Calleguas Municipal Water District isn't taking any chances.
When it built its new $23-million water treatment plant to comply with a 1991 state order, it went beyond the requirements to treat for such disease-causing agents as giardia, viruses and bacteria.
Calleguas, which serves up drinking water for half a million people in Ventura County, built a plant that will treat for cryptosporidium as well, using a sophisticated system of filters and ozone gas.
"There's no place for third-world water in Ventura County," said Calleguas General Manager Donald R. Kendall. "The only acceptable risk to the drinking public is zero."
Calleguas has the treatment plant on line on a trial basis and expects to have it under full power by December.
The dedication for the facility, which uses the ozone-filter system instead of the more traditional chlorine, is set for Oct. 12.
With the new plant, Calleguas comes into compliance with a 1991 order from the California Department of Health Services to upgrade its treatment plant. That order required all water districts to treat for the protozoa giardia; legionella, which causes Legionnaire's disease; viruses and common bacteria.
But ozone is the treatment of choice to knock out the most recently identified villain in some water supplies around the world: a protozoa called cryptosporidium, which causes flu-like symptoms, including diarrhea, and sometimes death.
A 1993 outbreak in Milwaukee sickened 400,000 people and killed more than 100, a California Department of Health Services official said.
There has never been an outbreak of cryptosporidium in the county. And as yet, the U.S. Environmental Protection Agency and the state Department of Health Services do not require treatment for it, although new rules that would require cryptosporidium treatment are under development, said John Curphey, sanitation engineer with the department's district offices in Santa Barbara.
"We commend Calleguas for using ozone," he said. "It's a good step on their part."
Much of the water supplied by Calleguas will not need to be treated by the new plant, since it comes from the Metropolitan Water District through the Jensen Treatment Plant.
But the district stores state project water in its reservoir, Lake Bard in Thousand Oaks, during the winter when water is less expensive and plentiful and draws it out for use during the summer. It is that water, or any water drawn from Bard during an emergency, that must be treated at the plant.
The water supplied by Calleguas goes to customers in Moorpark, Simi Valley and Thousand Oaks. In Camarillo and Oxnard, Calleguas water is blended with local ground water.
Two of the county's other three large districts that deliver surface water to customers are also in compliance with the 1991 order.
United Water Conservation District, which provides drinking water for about 150,000 people in Oxnard, Port Hueneme and the two Navy bases, uses an alternative but acceptable system of filtration, Curphey said.
The district, which receives state project water and stores it in Lake Piru, spreads water over filtration basins for percolation through 80 feet of sand into water basins below.
That water is then extracted and sent to Port Hueneme and Oxnard. Curphey said the sand acts as a natural filtration system, but the state required the district to create a new holding facility that allows the water longer contact with chlorine before it is pumped.
The city of Ventura, which uses water from the Ventura River, already has a treatment plant that filters water at the appropriate level.
Of all the large districts in the county, only the Casitas Municipal Water District is out of compliance.
However, Casitas, which serves about 50,000 people in west Ventura and the Ojai area, broke ground on its new $8.6-million plant last month.
Its plant, which will use a system that depends on filters and chlorine, is expected to be completed next June, said district General Manager John Johnson. But Johnson said the district's pilot tests show that it may be able to go beyond the present Health Department requirements.
"Our plant will meet all regulations," he said. "But we think we'll be able to get out the crypto-sized particles as well."
However, Curphey said that in most cases, chlorine isn't enough to filter out the tiny cryptosporidium particles. He also said that when new EPA and Health Department regulations are issued sometime in the future, Calleguas may have to alter its plant.
"Meanwhile," he said, "we have full confidence that the water is very safe."
The Calleguas plant works by taking water from the reservoir and adding ozone, which is in gas form.
"That provides the quick kill," said Susan Nielsen, manager of engineering for the district. "When the ozone gets into the water, it kills just about anything."
Kendall pointed to a huge cylindrical tank, with the word ozone printed on it.
"This is where it all happens," he said.
Then a coagulant chemical is added to the water so that the smallest particles cling together, making them easy to filter out as the water passes through a series of filters and baffles.
Some chlorine is still used to kill bacteria in the pipelines, but otherwise, it's the ozone that does most of the work, Kendall said.
"The risk with Calleguas water has always been extremely low," he said. "But when you tell someone the risk is low, that means there is a risk. The only risk the drinking public will accept is zero."