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...

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Pulsed lamps based on electric discharges in xenon are of interest for water treatment because they are free of mercury, have instant-on capability, and may provide enhanced effects due to the high irradiance of pulses or spectral differences. This study provides quantitative comparisons of standard mercury UV lamps with both a commercial flashlamp and a pulsed surface discharge lamp. Unlike mercury lamps, the UV performance of pulsed lamps is a function of operating parameters. In this study the measured UV efficiency of a flashlamp, with a specified practical lifetime, increased as the pulse length decreased, from 4.4% at 796 µs to 9.0% at 71 µs. The surface discharge lamp, which overcomes limitations of flashlamps, had a measured UV efficiency of 17% at 12 µs. In comparison, standard commercial low pressure and medium pressure mercury lamps evaluated in this study had UV efficiencies of 34.6% and 12.2%, respectively.Résumé : Les lampes à impulsions basées sur les décharges électriques dans le xénon sont intéressantes pour le traitement de l'eau puisqu'elles ne contiennent pas de mercure; elles possèdent la capacité d'être mises en marche instantanément et elles peuvent avoir des effets accrus en raison de la haute irradiance des impulsions ou des différences spectrales. La présente étude compare quantitativement les lampes standards UV à la vapeur de mercure avec des lampes-éclairs commerciales et une lampe à décharge superficielle à impulsions. Contrairement aux lampes à vapeur de mercure, le rendement UV des lampes à impulsions est fonction des paramètres de fonctionnement. Dans cette étude, l'efficacité mesurée d'une lampe-éclair UV, ayant une durée de vie utile spécifiée, augmentait à mesure que diminuait la longueur de l'impulsion, de 4,4 % à 796 µs à 9,0 % à 71 µs. La lampe à décharge superficielle, qui comble les limites des lampeséclairs, présentait une efficacité UV mesurée de 17 % à 12 µs. En comparaison, les lampes commerciales standards à faible et à moyenne pression de vapeur de mercure évaluées lors de cette étude présentaient respectivement des efficacités UV de 34,6 % et de 12,2 %.Mots-clés : UV à impulsions, traitement de l'eau, lampe-éclair, décharge superficielle, mercure.[Traduit par la Rédaction]

Field tests of a sparker system demonstrated control of zebra mussels in an intake pipe. The sparker was implemented in a wet well near the exit of an intake pipe at a Georgia-Pacific plant on Lake Champlain, N.Y. and was tested during the summer of 2003. The pressure was measured at several locations along the pipe, and zebra mussel samples were placed at those locations. Test results indicated that sparker pressure pulses can eradicate existing adult zebra mussels and prevent the settlement of larval stages. Sparker pressure pulses with peak pressures of at least 0.04 MPa and pressure energies per unit area of 0.16 J/m 2 per pulse appeared to prevent the settlement of veligers. Peak pressures of 0.23 MPa and pressure energies per unit area of 5.8 J/m 2 per pulse caused mortality of adult mussels. Z ebra and quagga mussels belong to the dreissenid family of nonindigenous invasive mussels found from north of the Great Lakes to the mouth of the Mississippi River in the south. The mussels are also found in Nevada, Arizona, California, and Colorado. Dreissenid mussels cause serious problems by clogging fixed screens and other system components in contact with raw water. The Nonindigenous Aquatic Nuisance Prevention and Control Act and its amendments mandate control of dreissenid mussel infestations (NISA, 1996; NANPCA, 1990). Although several control strategies are available, none is applicable to all situations or entirely problemfree. Chlorine effectively controls dreissenid mussels but produces disinfectant by-products, some of which are carcinogenic. Mechanical removal is also effective but is costly and may require plant shutdown.A nontoxic alternative uses pressure pulses to prevent the settlement and growth of dreissenid mussels and could also eradicate adult mussels. The technique reported here uses intense pressure pulses from a sparker. The pressure pulse is generated by high-power electrical arc discharge (pulse) between electrodes in water. The concept is illustrated in Figure 1. A pulsed electrical discharge rapidly heats and vaporizes liquid between two electrodes, producing a pressure shock. The emissions leave behind a high-pressure vaporized water cavity or "bubble," which expands to a maximum diameter and then contracts and collapses, producing another pressure pulse. This expansion and collapse repeats until the energy in RAYMOND SCHAEFER, RENATA CLAUDI, AND MICHAEL GRAPPERHAUS Opposing sparker electrodes are shown within the parabolic reflector that directs the pressure pulse down the intake pipe. The parabola is 35.6 cm in diameter with a focal length of 7 cm. 2010

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In this paper, an extracorporeal shock wave source composed of small ellipsoidal sparker units is described. The sparker units were arranged in an array designed to produce a coherent shock wave of sufficient strength to fracture kidney stones. The objective of this paper was to measure the acoustical output of this array of 18 individual sparker units and compare this array to commercial lithotripters. Representative waveforms acquired with a fiber-optic probe hydrophone at the geometric focus of the sparker array indicated that the sparker array produces a shock wave (P ∼40-47 MPa, P ∼2.5-5.0 MPa) similar to shock waves produced by a Dornier HM-3 or Dornier Compact S. The sparker array's pressure field map also appeared similar to the measurements from a HM-3 and Compact S. Compared to the HM-3, the electrohydraulic technology of the sparker array produced a more consistent SW pulse (shot-to-shot positive pressure value standard deviation of ±4.7 MPa vs ±3.3 MPa).

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Collimated beam (CB) tests allow for consistent, easily calculated and reproducible measurements of UV fluence, and are widely used in UV treatment research and validation testing. However, because CB tests employ distance to provide collimation, the irradiance at the test sample is much lower than in UV treatment systems. A potential benefit of pulsed light may arise from the high fluence rate it produces. A new high-irradiance (HI) test cell approach and modeling technique are presented for use in evaluating these effects. The model is shown to correctly predict the fluence in the HI test cell by benchmarking it to CB measurements. This demonstrates that the HI cell is a useful tool in evaluating the effect of high fluence rate in UV treatment. This modeling technique also has application in reactor design.Key words: pulsed UV, collimated beam, modeling, disinfection, remediation.