Researchers at the University of Denis Diderot in Paris and the VEOLLA Research Center in Maisons-Laffite have finally found a way to kill parasites found in water that are resistant to chlorine.
Parasites called Cryptosporidium that are resistant to chlorine are one of the most common causes of waterborne disease in the United States. Cryptosporidium induces disease with severe diarrhea, called cryptosporidiosis. The disease can also lead to death in people who have deficient immune systems, causing permanent and life-threatening diarrhea.
People acquire the disease when they ingest the parasite through the mouth by swallowing something that has been contaminated by an infected person’s or animal’s feces. They can also get it by swallowing food, water, or soil that contains the parasite. Since the parasite is resistant to chlorine it is very difficult to treat water for the parasite, and when drinking water becomes contaminated by it, it can lead to large outbreaks of cryptosporidiosis.
Outbreaks of cryptosporidiosis can happen very frequently. An outbreak affected the western half of the U.S. on September 21st, 2007 and infected 230 people in Idaho, hundreds in the Rocky Mountains, and 1, 600 in Utah. Also in 1993 the largest outbreak in the U.S. took place in Milwaukee. The Howard Avenue Water Purification Plant was contaminated by sewage that had passed into the plant through the filtration system. Over a two-week time period 403,300 became infected with the disease and over 100 people died.
New research performed at the Laboratory of Parasitology of the University of Denis Diderot and the VEOLIA Research Center has shown that Ultra Violet light actually kills the parasite. In the study, they contaminated water samples with large amounts of Cryptosporidium and passed the water samples under UV reactors.
The researchers tested the water under both medium-pressure and low-pressure reactors that are being used in the water industry. They the Cryptosporidium under the UV lights using a method of culturing cells that was developed by Emilio Entrala and used by the research team lead by Professor Francis Derouin’s in the Denis Diderot’s University Laboratory of Parasitology.
Under both strengths of UV reactors, the team saw that 99.998 percent of the parasites were unable to reproduce, proving that both polychromatic medium-pressure UV lamps and monochromatic low-pressure UV lamps and saw that both worked effectively to kill the parasites. They tested the lamps on volumes of water that resembled the number of water-distribution units found in both small and medium sized water treatment plants.
There study proved that industrial UV reactors can prevent waterborne disease outbreaks and make water safer for consumers.
Lucy Mansfield, “Ultraviolet light helps to secure water supply,” University of Denis Diderot.