No abstract

No abstract

The efficacy of UV and vacuum-UV (VUV) disinfection of Bacillus subtilis spores in aqueous suspensions at wavelengths of 172, 222 and 254 nm was evaluated. A Xe(2)* excilamp, a KrCl* excilamp and a low-pressure mercury lamp were used as almost monochromatic light sources at these three wavelengths. The first-order inactivation rate constants at 172, 222 and 254 nm were 0.0023, 0.122 and 0.069 cm(2) mJ(-1), respectively. Therefore, a 2 log reduction of B. subtilis spores was reached with fluences (UV doses) of 870, 21.6 and 40.4 mJ cm(-2) at these individual wavelengths. Consequently, for the inactivation of B. subtilis spores, VUV exposure at 172 nm is much less efficient than exposure at the other two wavelengths, while exposure at 222 nm is more efficient than that at 254 nm, which is probably because triplet energy transfer from DPA to thymine bases at 222 nm is higher than that at 254 nm. This research indicated quantitatively that VUV light is not practicable for microorganism disinfection in water and wastewater treatment. However, in comparison with other advanced oxidation processes (e.g. UV/TiO(2), UV/H(2)O(2) or O(3)/H(2)O(2)) the VUV-initiated photolysis of water is likely more efficient in generating hydroxyl radicals and more effective for the inactivation of microorganisms.

The concept of Electrical Energy per Order (EEO) was introduced in 2001 as a figure of merit for evaluating the energy requirements of ultraviolet-based advanced oxidation processes (UV AOPs) used for the degradation of various organic contaminants. The EEO parameter represents the energy input into the reactor that can achieve an order of magnitude decrease in the concentration of a target contaminant in a unit volume. Since the introduction of this parameter, it has become increasingly popular among UV AOP researchers and practitioners. However, the EEO is often reported without important details that affect the parameter, making its interpretation difficult. The EEO depends on a variety of factors (e.g. the concentration and identity of the target contaminant and the amount of hydrogen peroxide added). Therefore, the EEO parameter needs to be reported in the literature with several other experimental details affecting the reactor performance and in a way that proper comparisons can be made between reactors across studies or manufacturers. This paper discusses the proper application of the EEO parameter for bench-, pilot-, and full-scale studies. Sucralose (artificial sweetener, C12H19Cl3O8) is proposed as a standard substance for reactor comparison.

No abstract

No abstract

No abstract

This paper reviews recent experimental results concerning the use of modern excilamps (excimer lamps) in photoscience and photochemical technology. The special characteristics of these sources of incoherent vacuum-UV (VUV)/UV radiation are presented and their applications in water and air remediation are discussed. Special attention is paid to the VUV (172 nm)-initiated oxidation and mineralization of organic water and air contaminants. For example, the VUV-initiated production of carbon dioxide and carbon monoxide during 172 nm irradiation of several saturated volatile organic substrates in the gas phase (e. g. methanol, ethanol, 2-propanol, 1,4-dioxane, cyclohexane, and n-hexane) was quantitatively verified by gas chromatography. Depending on the nature of the gaseous substrate and on the flow rate through the excimer-flow-through photoreactor different CO 2 /CO ratios were obtained.Résumé : Cet article revoit les récents résultats expérimentaux sur l'utilisation d'excilampes (lampes excimères) modernes dans la technologie de la science photoélectrique et photochimique. Les caractéristiques spéciales de ces sources de rayonnement incohérent sous vide UV (VUV)/UV sont présentées et leur utilisation pour la réhabilitation de l'eau et de l'air est abordée. Une attention spéciale est apportée à l'oxydation et à la minéralisation initiées par VUV (172 nm) des contaminants organiques dans l'eau et l'air. Par exemple, la production de dioxyde de carbone et de monoxyde de carbone initiée par VUV au cours d'une radioexposition à 172 nm dans plusieurs substrats organiques volatils saturés dans la phase gazeuse (p. ex. méthanol, éthanol, propan-2-ol, 1,4-dioxane, cyclohexane et n-hexane) a été vérifiée quantitativement par chromatographie en phase gazeuse. Différents rapports CO 2 /CO ont été obtenus selon la nature du substrat gazeux et selon le débit à travers le photoréacteur excimère à écoulement continu.Mots-clés : lampes excimères, excilampes, radioexposition à 172 nm, oxydation aux ultraviolets du vide, photominéra-lisation, désinfection aux UV, photoréacteur excilampe à circulation d'échantillon, photoréacteur à écoulement piston, photo-oxydation en phase gazeuse.[Traduit par la Rédaction]