Logic says that at least some of those crypto sufferers contracted the disease from tap water.
Science does not yet know just how much crypto it takes to make you sick. Nor does anyone understand how it travels. In fact, there is no good way to measure it, in raw or treated water.
But because sludge is the end product of the filtering process, that is where the cryptosporidium most likely ends up, this time in concentrates that downstream water plants don't want to deal with.
And so, as the crypto breeds, a battle brews.
"Virtually every other discharger, any other water treatment plant in the country, does some kind of [solids] removal," says Catherine Kuhlman, chief of the permits andcompliance branch of the Environmental Protection Agency. "That is the standard practice. So I think it's reasonable for Phoenix to expect that they're going to haveto do some kind of removal."
But the City of Phoenix does not want to shell out $60 million to $80 million to build new facilities to keep the sludge out of the SRP canals.
So SRP upped the ante by raising the question of cryptosporidium. And the cities of Tempe and Chandler, whose water treatment plants lie downstream from Phoenix, have lined up alongside SRP to protest. They argue that, as long as there is a health risk, the City of Phoenix should act responsibly to eliminate it.
The City of Phoenix recently completed a study of cryptosporidium levels in the SRP canals that it claims proves that the dumping does not increase crypto levels.
Tempe water officials have characterized that study as nothing more than "a snapshot." SRP officials have gone further to say that the study, as flawed as it is, still shows increased crypto levels downstream from Phoenix water treatment plants.
While Tempe and Chandler already dispose of the sludge from their water treatment plants, in Phoenix, cost-benefit thinking prevails.
Health risks or no, within the next year, federal regulators will likely tell Phoenix to take care of its own sludge--unless Phoenix Mayor Skip Rimsza can find relief from any potential EPA directives.
He's hoping Congress helps him preserve the bottom line in the dirt fight.
In their argument against sludge removal, Phoenix officials fall back on the fact that cryptosporidium appears naturally in most surface waters.
"It's been there for eons," says Bing Brown, a Phoenix water department spokesman. "In the levels we're talking about, with or without that sludge, it is in very low quantity."
And since there have been no major outbreaks in Phoenix so far, Brown reasons, it's unlikely there will be problems in the future.
He may be right; he may be wrong.
The Centers for Disease Control estimate that 940,000 people are sickened each year by waterborne illnesses in tap water, and 900 die.
And in 1993, 400,000 people in Milwaukee, Wisconsin, came down with cryptosporidiosis, and 100 died.
The Milwaukee outbreak was blamed on human error in a water treatment plant. In 1994, 35 persons died from cryptosporidiosis in Las Vegas, and there have been outbreaks as well in Georgia and Washington state.
There is no treatment for cryptosporidiosis; generally, healthy people can shake the diarrhea in a couple of unpleasant weeks. But recent organ-transplant recipients, persons going through chemotherapy for cancer, and AIDS patients can't recover from it.
"They'll have 15 to 20 watery bowel movements a day," says Fisher. It is diarrhea that can be slowed down only by heavy-duty medicines, in some cases, opium. And the diarrhea leads to extreme dehydration and electrolyte loss. In Milwaukee, the disease struck sufferers of rheumatoid arthritis and ulcerative colitis almost as viciously as it struck bone-marrow-transplant recipients and AIDS patients. Those children and adults with immune-system deficits who didn't die quickly lingered for months, unable to work or even eat. Some victims who had been healthy before contracting crypto were left with rare blood disorders and infected spleens that had to be removed.
Last March, Phoenix water department head Mike Gritzuk issued a press release saying "We strongly support AWWA's [American Water Works Association] and EPA's national effort to protect consumers from cryptosporidium."
According to guidelines issued by the American Water Works Association, the best crypto-prevention program keeps the parasite from getting into the water supply in the first place. The association was focused on moving it out of watersheds used for drinking supplies; SRP has argued that dumping crypto-loaded sludge into the water violates that guideline.
Back in his SRP office, Paul Cherrington sets two tall jars of water on a conference table to use as visual aids.