New York City has opened the world’s largest water disinfection plant, using ultraviolet (UV) light as a sanitizing agent to eliminate cryptosporidium, giardia and other pathogenic microorganisms that can cause nausea, cramps, diarrhea and more serious ailments. Fifty-six massive UV units will neutralize waterborne pathogens in all drinking water derived from the city’s major sources.
The Catskill and the Delaware water supply systems, completed in 1927 and 1967, respectively, provide about 90 percent of the city’s water. The facility will process up to 9 billion liters daily, adding a second layer of sanitation to the city’s traditional chlorine treatment. While cryptosporidium is highly resistant to chlorine, UV has proved effective at controlling the parasite. Adenovirus is resistant to UV disinfection, but can be killed using chlorine.
The U.S. Environmental Protection Agency requires that if unfiltered surface water treatment systems don’t filter drinking water, another barrier for microorganisms besides chlorine treatment needs to be installed. The alternative to UV would have been to build a much more expensive filtration facility that passes drinking water through a series of porous materials such as layers of sand, gravel and charcoal to remove chemicals, hazardous materials and toxins.
Source: Scientific American