Ultraviolet answer to chlorine-resistant bugs

Research lead

Researchers from the University Denis Diderot in Paris, working in collaboration with the VEOLIA Research Centre in Maisons-Laffitte, France, have shown that chlorine-resistant Cryptosporidium parasites, which cause diarrhoeal disease in humans and can lead to significant mortality in children and the immunocompromised, can be inactivated by exposure to industrial UV reactors.

Cryptosporidium contamination of drinking water supplies is a major public health problem. An outbreak in Galway City in Ireland in March this year affected more than 170 people, and left the city’s tap water unsuitable for food preparation or drinking over several weeks.

Now the French researchers have shown UV light can be used to kill Cryptosporidium that are not susceptible to conventional chlorine disinfection.

In the study water was experimentally contaminated with large amounts of Cryptosporidium oocysts and then passed through two different types of UV reactor. The efficacy of the reactors was assessed using a cell culture method.

Over 99.9 percent of Cryptospridium were inactivated in both polychromatic medium-pressure and monochromatic low-pressure UV lamps, in conditions that closely modelled typical small- or medium-sized water treatment units.

Cedric Féliers, of the VEOLIA Research Centre ,said, “These tests, made in near real conditions, confirm that these industrial UV reactors could prevent waterborne outbreaks and secure water supply to customers.”