Water Industry News

World's biggest UV water treatment plant coming
to New York City


July 18, 2005)

MOUNT PLEASANT Work is scheduled to begin by September on the world's largest ultraviolet water treatment plant, a nearly $600 million facility designed to sterilize two pesky parasites that have roots in a disease outbreak that sickened 400,000 people in Milwaukee a dozen years ago.

To be built on the Grasslands reservation next to the county jail in Mount Pleasant, the UV plant can treat up to 2.4 billion gallons of water a day from New York City's two largest reservoir systems, the Catskill and the Delaware, which are the source of most water used by Westchester and New York City.

The plant will mean at least another $2.3 million annually in tax revenue for the town of Mount Pleasant, the Pocantico Hills schools and Westchester County.

The massive project stems from a campaign against two single-cell organisms giardia and cryptosporidium. Though these parasites may have little or no effect on healthy people, they can cause severe diarrhea and other gastrointestinal symptoms, which can kill individuals with impaired immune systems.

The presence of these two organisms led to a brief water alert two weeks ago in New York City after a torrential rain washed soil and some parasites into the Kensico Reservoir. That alert called for the elderly, the very young and others with weakened immune systems to boil tap water or drink bottled water.

It was a massive outbreak of cryptosporidium infections in Milwaukee and its suburbs in 1993 that set the nation on a series of upgrades to its water supplies. Triggered by a malfunction at a water treatment plant, the outbreak struck 403,000 people, hospitalizing 4,400 and killing 69, according to the federal Centers for Disease Control and Prevention.

"We hadn't seen anything like this and it really was the wake-up call for the water-supply industry," said Michael Principe, director of the New York City Bureau of Water Supply and deputy environmental protection commissioner.

Long used in Europe, ultraviolet disinfection is a simple concept: giardia and cryptosporidium in untreated drinking water are rendered harmless when they are exposed to ultraviolet radiation before they reach kitchen faucets. The UV rays come from 56 chambers containing a series of 10-foot-long light tubes.

"People are amazed to learn that a light that is very much like what you have in an office or classroom can disinfect water," said Deborah Keesler, the Department of Environmental Protection engineer who is overseeing the project.

The lights are different from fluorescent lights in one essential way, though: They emit a powerful dose of ultraviolet rays in particular, UV-C waves that disrupts the DNA of giardia and cryptosporidium, preventing them from multiplying and causing infections.

Ultraviolet light is particularly important in treating cryptosporidium, which withstands normal chlorine treatment, a major weapon against microbes in water.

"Cryptosporidium looks at chlorine and just laughs. Nothing happens to them," said Karl Linden, an engineer at Duke University and an expert on UV disinfection.

Chlorine levels would need to be boosted 100 times, Linden said, to become effective against cryptosporidium. Health officials, however, are trying to reduce chlorine use in water. That's because chlorine is a highly reactive element that readily combines with organic molecules in water to form an array of potentially carcinogenic and genetically damaging chemicals.

"A big benefit of UV is that you are not adding a chemical," Principe said, "and we believe it will allows us to reduce the amount of chlorine that we now use."

Chlorine is likely to remain a public health weapon, however, because it is effective against bacteria; UV light is typically less effective against bacteria, officials say.

Though it took the Milwaukee cryptosporidium outbreak to push the nation to take action, researchers were becoming aware of the problem posed by the parasites over the previous decade. Traditionally the biggest biological threat to water supplies came from the better-known problem of bacteria in human and animal waste.

"It is the old story that as technology improves you find more and more things in there that you didn't know about," Linden said.

Ironically, improving medical technology means more people may be at risk from giardia and cryptosporidium, increasing the need to find an effective treatment.

"As medicine makes advances we are able to keep people alive with weakened immune systems, whether it is organ transplants, cancer, HIV. That means more people are at risk from serious, even fatal consequences," Westchester Health Commissioner Joshua Lipsman said.

Westchester has recorded roughly eight to 10 cryptosporidium cases and about 130 to 150 giardia cases in recent years; New York City received reports of 126 cases of cryptosporidium and 1,214 cases of giardia, according to health officials there.

Giardia and cryptosporidium typically get in public water supplies from farm and wild animals.

Construction of the UV plant will be a massive project not expected to be complete until 2010. The two-story UV plant will be a large building, 410 feet by 200 feet. One floor will be underground and the other above ground level, varying in height from 30 to 50 feet.

It will take some 18 months just to dig out the below-grade level and otherwise ready the site for construction, Keesler said. The excavated soil will not go to waste, though; it will be used to cover and landscape two large concrete fields west of the Kensico Reservoir that had been used to aerate drinking water supplies.

Far from fighting the massive project, Mount Pleasant is welcoming it with open arms. The project will vault the New York City Department of Water Supply over Consolidated Edison as the biggest taxpayer in Mount Pleasant. The bureau would pay $8.6 million annually compared with Con Ed's $7.1 million based on current rates in town, school and county taxes, according to New York City estimates, which Mount Pleasant Supervisor Robert Meehan said might be on the low side.

"The impacts will be very little and it will be a major generator of taxes," Meehan said. "People are surprised to learn that New York City is such a major payer of taxes here."

UV disinfection and chlorine, however, do not replace watershed protection that prevents giardia, cryptosporidium and other contaminants from getting into the water in the first place, officials say.

Water from the Catskill and Delaware systems is unusually clean, allowing the city to avoid building a water filtration plant costing up to $8 billion, Principe said. That is in sharp contrast to water from the much smaller Croton system, for which federal officials are requiring construction of a water filtration plant costing some $1.4 billion in Van Cortlandt Park in the Bronx.

"It is not an either-or situation," said Eric Goldstein, a senior attorney with the Manhattan-based Natural Resources Defense Council. "You need technology like UV and you need to preserve land to prevent pollution at the source."