EN ROUTE: The Catskill Water Supply System, completed in 1927, and the Delaware Water Supply System, completed in 1967, provide about 90 percent of New York’s water supply. The combined Catskill/Delaware watershed cover 4,145 square kilometers.
Image: Courtesy of the U.S. Environmental Protection Agency (EPA)
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As World Water Week celebrates its 21st anniversary in Stockholm this week, New York City is two months away from opening the world's largest ultraviolet (UV) drinking-water disinfection plant. When the lights go on, the facility's 56 massive UV units will neutralize waterborne pathogens in all the drinking water coming from the city's major sources—the Delaware County and Catskill watersheds. The facility will process up to nine billion liters daily, adding a second layer of sanitation to the chlorine treatment that has been applied for years.
The Delaware–Catskill watersheds, located 160 kilometers north of the metropolis, have historically not required filtration or multiple methods of disinfection. More stringent U.S. Environmental Protection Agency (EPA) regulations in recent years and increased development around these bodies of water over the past decade, however, have prompted the city to add more protection against potentially disease-causing microorganisms.
The new, $1.6-billion Catskill–Delaware Ultraviolet Disinfection Facility—built some 50 kilometers north of Manhattan on 62 hectares in the towns of Mount Pleasant and Greenburgh in Westchester County, N.Y.—is scheduled to go live by October 29. As water flows through each of its 151-million-liter disinfection units, the UV light will alter the DNA of cryptosporidium, giardia and other waterborne pathogens, rendering them unable to replicate. Blooms of these microorganisms can cause nausea, cramps, diarrhea and even more serious maladies.
Water-flow pipes connect to either end of the 7,200-kilogram rectangular stainless steel UV disinfection reactors, each of which is about 5.8 meters long, 1.7 meters wide and 2.3 meters tall. Water moves through each reactor at about 1.5 meters per second, passing within centimeters of that unit's 210 UV lamps. The Catskill–Delaware facility as a whole is expected to use up to 6.3 megawatts of power when the water is at the maximum flow. On normal days, when about five billion liters are flowing, energy usage should not exceed 4.5 megawatts, according to Trojan Technologies, Inc., the wholly owned subsidiary of Danaher Corp., which built the facility.
Trojan's operation will dwarf the San Francisco Public Utilities Commission's Tesla Treatment Facility, which opened in July 2011. That $114-million project is California's largest UV water disinfection facility, treating up to 1.2 billion liters of water per day for the Bay Area from the Hetch Hetchy Reservoir in Yosemite National Park.
In 2006 the EPA began requiring unfiltered surface water treatment systems, including the one delivering New York City's drinking water, to either filter its drinking water or install some other barrier for microorganisms besides chlorine treatment. The city's alternative to UV would have been to build a much more expensive filtration facility (pdf) that passed drinking water through a series of porous materials—typically layers of sand, gravel and charcoal—helping to remove tiny chemicals, hazardous materials and toxins.
The EPA's requirements make sense, given that neither chlorine nor UV treatments can by themselves mitigate all threats to drinking water. Whereas cryptosporidium is highly resistant to chlorine, UV has proved effective at controlling the parasite. On the other hand, adenovirus is notoriously resistant to UV disinfection but can be killed using chlorine.
Although adenovirus is not typically found in surface water repositories, New York's watersheds are not entirely free of risk because of the growing population and increased development in those areas, says Mark Sobsey, University of North Carolina at Chapel Hill professor of environmental sciences and engineering and director of the school's Environmental Microbiology Laboratory. "We have to assume that there is some risk of adenoviruses getting into these water sources from human fecal contamination, such as septic tank effluents that may discharge into some waters and eventually enter the reservoirs," he adds.
The good news—between the new UV facility and the requirement that all municipal and community drinking water supplies use a chemical disinfectant, any risk that adenovirus would contaminate the city's water supply is negligible, Sobsey says.
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13 Comments
Add CommentRather than invest all this money and energy into treatment, wouldn't it be better and cheaper to make sure the watersheds are clean? For example, why not guarantee proper sewers to all houses in the watershed, instead of making them use septic tanks? Vienna, for example, protects its watershed to such a degree that they don't treat their water at all, and it's the best tasting city water that I've ever drank.
Reply | Report Abuse | Link to thishttp://www.wien.gv.at/english/environment/watersupply/supply/way.html
lump1,
Reply | Report Abuse | Link to thisIt's possible the engineers and project managers did a review and analysis of the project and alternatives and decided on the most feasible and economic course of action and implementation. Projects of this scale often have this kind of management and planning. (Did you think it wouldn't?)
Another very worrisome problem that needs to be urgently addressed is the insidious presence of pharmaceutical, agricultural & industrial contaminants found in our drinking water supply. The Chicago water quality reports acknowledge but does not do anything about these chemicals because there seems to be no particular guidelines on what to do. Current Filtration and UV treatments do NOT address this problem.
Reply | Report Abuse | Link to thislump1,
Reply | Report Abuse | Link to thiswhile watershed protection is certainly important the difference you have not realizes is thesupply for Vienna is groundwater while New York uses surface water. Vienna can get away without treatment because they are tapping into a confined aquifer that has no external influences (or has to filter through a lot of soil before it gets there). Birds and other animals use surface waters which actually contribute to most of the contamination. No amount of watershed protection will prevent animals from defecating in your water supply.
This also reflects our tendency to seek centralized solutions, which, not surprisingly,increase capital accumulation for few, versus dispersed solutions.
Reply | Report Abuse | Link to thiscflora,
Reply | Report Abuse | Link to thisOur tendency for centralized solutions is most often driven by their efficiency in terms of implementation and maintenance, not conspiracy theories about 'capital accumulation for few'.
lamorpa,
Reply | Report Abuse | Link to thisCflora doesn't mention conspiracy s/he's referring to how our economy has worked since at least the industrial revolution.
Nowadays we can dcentralise home water treatment, electrical generation and etc. ..
Though i think it's clear that dispersed solutions can also be centrally owned and the surplus capital can be centrally collected.
Nothing wrong with that. I'd lease a cradle to grave home water treatment plant if I could also I'd be more interested in PV panels if I were leasing the solution and knew that they would be recycled.
How effective is the UV treatment against drinking water supplies that contain bacteries and virus? To what percent can we be sure that our drinking water is free of those pathogens?
Reply | Report Abuse | Link to thishttp://www.sciencedaily.com/releases/2009/02/090212093941.htm
Reply | Report Abuse | Link to thisThe New York Times, and the millionaires that sponsor, block my comments on Oceanogenic Power simply because take advantage these media to report on this discovery of the third world, significant for everyone.
Reply | Report Abuse | Link to thisWith this energy converted into electricity, clean, cheap and enough, and superconducting lines, would be carried all the energy it needs New York or any city in the world, and on-site, may be distill: hydrogen and oxygen and after using these to generate other types of energy, and proportionally, and also in site, would occur water, super pasteurized, and fresh.
But for the New York Times, is better to inform, as a good thing: to use only for the passage of vessels by the Panama Canal; 2000 million gallons daily of fresh water that; reporting on a solution to the thirst for water, and clean energy in the world.
@Windontree
Reply | Report Abuse | Link to thisTrojanUV actually does have several products that treat pesticides and pharmaceuticals. They are currently installed and working at sites all over the world.
@rja2012
Reply | Report Abuse | Link to thisUV is very effective at treating specific pathogens. Some respond better to UV and others to Chlorine. UV systems for drinking water are validated by a third party. If there is a failure in the system the plant is alerted and that water is then diverted from the distribution system. TrojanUV has systems validated to inactivate 4 Log virus, which is 99.99%.
I'm glad to see NYC add UV treatment. This should decrease the levels of carcinogenic disinfection byproducts due to chlorination. I also agree with the person who suggests that watershed protection is a great investment. Cities like Seattle that control the entire watershed they use have much less risk of contamination due to human activity.
Reply | Report Abuse | Link to thisIssues such as contamination with pharmaceuticals and anything else that people consume and then urinate are present primarily when river or lake water is the source and there are cities that dump treated sewage into the water supply (estimated at some 43 mil Americans by AP). Currently only reverse osmosis is proven to remove these contaminants from drinking water although a granular activated carbon filter will reduce levels.
This problem started with the invention of the toilet and the centralization of sewage, as referenced above. I hear that Bill Gates is working on an alternative to the toilet but I personally don't see a way to move past using water as a conveyor of our waste products. I hope he discovers something.
We must also keep in mind that everyones' water is different, will have varying physical characteristics and different contaminants. The only way to know how to treat your own water is to look at the water report provided by your local supplier and then treat the water to remove those contaminats which are actually present. You can follow my free 5 Steps to Healthy Water and make sure you are protected. http://www.cleanairpurewater.com
To your health... Jim