Adenovirus is recognized as the most UV-resistant waterborne pathogen of concern to public health microbiologists. The U.S. EPA has stipulated that a UV fluence (dose) of 186 mJ cm ؊2 is required for 4-log inactivation credit in water treatment. However, all adenovirus inactivation data to date published in the peer-reviewed literature have been based on UV disinfection experiments using UV irradiation at 253.7 nm produced from a conventional low-pressure UV source. The work reported here presents inactivation data for adenovirus based on polychromatic UV sources and details the significant enhancement in inactivation achieved using these polychromatic sources. When full-spectrum, medium-pressure UV lamps were used, 4-log inactivation of adenovirus type 40 is achieved at a UV fluence of less than 60 mJ cm ؊2 and a surface discharge pulsed UV source required a UV fluence of less than 40 mJ cm ؊2 . The action spectrum for adenovirus type 2 was also developed and partially explains the improved inactivation based on enhancements at wavelengths below 230 nm. Implications for water treatment, public health, and the future of UV regulations for virus disinfection are discussed.UV disinfection is a well-accepted technology for inactivation of bacterial and protozoan pathogens. Until recently, UV was also considered a viable technology for disinfection of viruses. At UV fluences (doses) typically used in water disinfection, UV is very effective (Ͼ4-log inactivation) against almost all known pathogenic viruses, with the one exception of adenoviruses (5). Adenovirus has been recently listed on the U.S. EPA Candidate Contaminant List, which indicates that it is a high priority for possible future regulation and is known or anticipated to occur in public water systems, but significant data gaps need to be addressed before regulation can be invoked. According to recently published U.S. EPA regulations (17), the inactivation of adenoviruses to a level of 4 log requires a UV fluence of 186 mJ cm Ϫ2 , based on an 80% credible interval, as presented in the Draft UV Disinfection Guidance Manual (16). The U.S. EPA-regulated UV fluence for inactivation of all viruses is now based on the conservative case of adenoviruses. Yates et al. (18) provide an excellent review of the issues surrounding the UV inactivation of adenovirus.Although data sets for UV inactivation of adenovirus differ moderately, they all place adenovirus as the most UV-resistant health-related virus known. However, all peer-reviewed published studies to date have been performed using a low-pressure (LP) mercury vapor UV lamp source characterized by a monochromatic output in the UV range at 253.7 nm. Based on these LP UV irradiation studies, the UV fluence necessary to achieve 4-log inactivation of adenovirus varies from 120 to approximately 180 mJ cm Ϫ2 . For adenovirus type 5 (Ad5), the required UV fluence is 160 to 170 mJ cm Ϫ2 (1), which is similar to those required for Ad1 (9), Ad2 (1, 5), Ad6 (9), and Ad40 and Ad41 (8). However, there are two studies that repo...

The dosage of ultraviolet (UV) light required to inactivate adenoviruses serves as the basis for virus inactivation requirements in the Long Term 2 Enhanced Surface Water Treatment Rule.The rule increases the required UV dose from the standard practice of 40 mJ/cm 2 to 186 mJ/cm 2 for 4-log inactivation. Ensuring this delivered dose in the UV reactor requires accounting for uncertainties in the reactor validation testing, which results in an applied UV dose of 200-300 mJ/cm 2 for 4-log virus inactivation credit for a given UV reactor. Concerned about the potential effect of this action on drinking water treatment, a group of experts met to assess the state of the science with respect to adenoviruses in drinking water. This working group reviewed the current science on adenoviruses and identified the effects-positive and negative-on public health protection arising from the elevation of UV design target doses.

Bench-scale experiments determined the inactivation rates of adenovirus serotype 2 with low-pressure, high-output ultraviolet (UV) light, chlorine (Cl 2 ), and preformed chloramines.Studies with sequential chloramines were also done to mimic water treatment practices. Sequential experiments with adenovirus serotype 2 suspended in laboratory-grade water and natural waters containing ammonia were exposed to either UV light followed by Cl 2 /chloramines or the reverse sequence. Adenovirus log reductions were quantified through cell culture techniques. A free Cl 2 C × T (concentration × time) of 1.22 mg-min/L resulted in a 3.72-log reduction, a preformed chloramine C × T of 264.5 mg-min/L resulted in a 1.2-log reduction, a sequential chloramine C × T of 40.5 mg-min/L resulted in a 1-log reduction, and a UV dose of 40 mJ/cm 2 resulted in a 1-log reduction. Up to 4-log reductions were achieved with a UV dose of 40 mJ/cm 2 followed by a sequential chloramine C × T of 27.2 mg-min/L. This suggests that sequential disinfection may be the best option for dealing with UV-resistant organisms such as adenoviruses.

Anthropogenic compounds known as per- and polyfluoroalkyl substances (PFAS) represent a major class of contaminants of emerging concern composed of nearly 5000 chemicals. Many PFAS are persistent, bioaccumulative and toxic,...

A water sample in the petri dish is exposed to ultraviolet light at the bottom of the collimated-beam device.In the lab, researchers use petri dishes and other equipment to enumerate the bacteria. 2004