Scientists report in the June 2003 edition of the Journal AWWA of the American Water Works Association that tests conducted on a new U.S. water disinfection technology have observed the delivery of extremely high germicidal doses of ultraviolet (UV) light that suggest the ability to defeat a contamination of water supplies by known and listed biological pathogens, including the anthrax spore.
In the report entitled "Pulsed UV Unit May Inactivate Biological Agents," Dr. Egon Weber and Karl Scheible from HydroQual Inc. report the results of their September 2002 tests conducted on a new water disinfection machine developed by LightStream Technologies of Reston, VA. HydroQual is one of the leading scientific research firms on UV technologies and is frequently used by the U.S. Environmental Protection Agency for expert guidance on UV technologies, testing and procedures.
The LightStream machine tested by the HydroQual uses a mechanism for delivery of UV light, known as "pulsed UV," that produces short pulses of UV light of extremely high intensities -- up to 6 million watts each pulse that can be repeated up to 30 times per second -- as water flows through the machine. The machine was developed to disinfect up to one million gallons per day of ordinary water and wastewater and was adapted for these tests to simulate flows of approximately 100,000 gallons per day associated with buildings, facilities or small community water systems.
Ultraviolet light, in wavelengths very similar to that of sunlight and delivered in sufficient amounts, or "doses", breaks the DNA of bacteria, viruses and other pathogens. This damage to the DNA renders the dangerous pathogens harmless. To quantify the "dose" delivered by the LightStream machine, the scientists conducted testing known as "biodosimetry" or "bioassay" challenge tests that use a substitute organism to measure the amount of inactivation achieved by the disinfection technology. Such procedures are used for UV reactor validation testing, and are very often required by regulatory agencies. From this data, scientists can estimate the germicidal dose delivered by a source of UV light.
According to the scientists' report, the very high doses delivered by the LightStream machine were "at the upper limit of current ability to measure UV using a common substitute indicator organism." Such high doses, the scientists reported, were "in the range required for approximately 5 - 6 log reductions (99.9999%) of the anthrax spore (Bacillus anthracis), the more resistant of the known, listed and pathogenic bacteria and viruses," and that "Greater log reductions would be expected for other, more sensitive, listed and known pathogenic bacteria and viruses."
A PDF version of the AWWA article can be viewed and downloaded at http://www.awwa.org/communications/journal/News/0603security.pdf
