Medium Pressure UV Research Articles

The effect of UV/H 2O 2 treatment on disinfection by-product formation potential under simulated distribution system conditions

Advanced oxidation with ultraviolet light and hydrogen peroxide (UV/H 2O 2) produces hydroxyl radicals that have the potential to degrade a wide-range of organic micro-pollutants in water. Yet, when this technology is used to reduce target contaminants, natural organic matter can be altered. This study evaluated disinfection by-product (DBP) precursor formation for UV/H 2O 2 while reducing trace organic contaminants in natural water (>90% for target pharmaceuticals, pesticides and taste and odor producing compounds and 80% atrazine degradation). A year-long UV/H 2O 2 pilot study was conducted to evaluate DBP precursor formation with varying water quality. The UV pilot reactors were operated to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for DBP precursor formation. Two process waters of differing quality were used as pilot influent, i.e., before and after granular activated carbon adsorption. DBP precursors increased under most of the conditions studied. Regulated trihalomethane formation potential increased through the UV/H 2O 2 reactors from 20 to 118%, depending on temperature and water quality. When Post-GAC water served as reactor influent, less DBPs were produced in comparison to conventionally treated water. Haloacetic acid (HAA5) increased when conventionally treated water served as UV/H 2O 2 pilot influent, but only increased slightly (MP lamp) when GAC treated water served as pilot influent. No difference in 3-day simulated distribution system DBP concentration was observed between LP and MP UV reactors when 80% atrazine degradation was targeted.

Biofilm control in water by a UV-based advanced oxidation process

An ultraviolet (UV)-based advanced oxidation process (AOP), with hydrogen peroxide and medium-pressure (MP) UV light (H2O2/UV), was used as a pretreatment strategy for biofilm control in water. Suspended Pseudomonas aeruginosa cells were exposed to UV-based AOP treatment, and the adherent biofilm formed by the surviving cells was monitored. Control experiments using H2O2 or MP UV irradiation alone could inhibit biofilm formation for only short periods of time (<24 h) post-treatment. In a H2O2/filtered-UV (>295 nm) system, an additive effect on biofilm control was shown vs filtered-UV irradiation alone, probably due to activity of the added hydroxyl radical (OH•). In a H2O2/full-UV (ie full UV spectrum, not filtered) system, this result was not obtained, possibly due to the germicidal UV photons overwhelming the AOP system. Generally, however, H2O2/UV prevented biofilm formation for longer periods (days) only when maintained with residual H2O2. The ratio of surviving bacterial concentration post-treatment to residual H2O2 concentration played an important role in biofilm prevention and bacterial regrowth. H2O2 treatments alone resulted in poorer biofilm control compared to UV-based AOP treatments maintained with similar levels of residual H2O2, indicating a possible advantage of AOP.

Inactivation of human adenovirus by sequential disinfection with an alternative UV technology and free chlorine

There has been growing concern over human exposure to adenoviruses through drinking water due to the extreme resistance of human adenoviruses to the traditional UV technology (low-pressure (LP) UV). As an effort to develop an effective treatment strategy against human adenoviruses in drinking water, we determined the effectiveness of sequential disinfection with an alternative UV technology (medium-pressure (MP) UV) and free chlorine. Human adenovirus 2 (Ad2) was irradiated with a low dose of MP UV irradiation (10 mJ/cm(2)) through UV collimated apparatus and then exposed to a low dose of free chlorine (0.17 mg/L) at pH 8 and 5°C using a bench-scale chemical disinfection system. A significant inactivation (e.g. 4 log(10)) of Ad2 was achieved with the low doses of MP UV and free chlorine within a very short contact time (∼1.5 min) although there was no apparent synergistic effect on Ad2 between MP UV and free chlorine. Overall, it is likely that the sequential disinfection with UV irradiation and free chlorine should control the contamination of drinking water by human adenoviruses within practical doses of UV and free chlorine typically used in drinking water treatment processes.

Efficient electrochemical decomposition of perfluorocarboxylic acids by the use of a boron-doped diamond electrode

The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant ( k 1) of 2.4 × 10 − 2 dm 3 h − 1 . Under the present reaction conditions, k 1 increased with increasing current density and saturated at values over 0.60 mA cm − 2 . Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C–C bond between the C 7F 15 and COOH in PFOA and generates a C 7F 15 radical and CO 2. The C 7F 15 radical forms the thermally unstable alcohol C 7F 15OH, which undergoes F − elimination to form C 6F 13COF. This acid fluoride undergoes hydrolysis to yield another F − and the perfluorocarboxylic acid with one less CF 2 unit, C 6F 13COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO 2 and F −. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface.

Molecular Indications of Protein Damage in Adenoviruses after UV Disinfection

Adenoviruses are resistant to monochromatic, low-pressure (LP) UV disinfection--but have been shown to be susceptible to inactivation by polychromatic, medium-pressure (MP) UV--when assayed using cell culture infectivity. One possible explanation for the difference between UV lamp types is that the additional UV wavelengths emitted by MP UV enable it to cause greater damage to viral proteins than LP UV. The objective of this study was to examine protein damage in adenoviruses treated with LP and MP UV. Results show that MP UV is more effective at damaging viral proteins at high UV doses, though LP UV caused some damage as well. To our knowledge, this study is the first to investigate protein damage in UV-treated adenovirus, and the overview presented here is expected to provide a basis for further, more detailed work.

Comparison of Low Pressure and Medium Pressure UV Lamps for UV/H2O2 Treatment of Natural Waters Containing Micro Pollutants

UV/H2O2 advanced oxidation is an effective barrier against organic micro pollutants. Several studies have focused on the degradation of a wide range of pollutants, but regarding the comparison of low-pressure mercury lamps (LP) with medium-pressure mercury lamps (MP) with respect to energy consumption by the UV/H2O2 process, little is known so far. Although the absorbance of H2O2 at 254 nm is low, the results of this research show that the yield of hydroxyl radical formation (OHCT) with LP lamps is comparable or higher than with MP lamps. In a water matrix with a background absorbance due to organics and nitrate, H2O2 absorbs UV light very effectively at 254 nm. Generally, due to the contribution of direct photolysis, the degradation of pollutants is better with MP-UV/H2O2 than with LP-UV/H2O2 at the same UV fluence. Therefore, with LP-UV/H2O2 micro pollutants are predominantly degraded through reaction with OH radicals. However, due to the much higher efficiency of LP lamps in converting electrical energy to UV-C light, the energy required to achieve 90% degradation (EEO) of pesticides and pharmaceuticals can be significantly lower with LP-UV/H2O2 than with MP-UV/H2O2. Results of bench-scale tests show EEO data of the LP-UV/H2O2 process to be 30%–50% lower than for the MP-UV/H2O2 process. At these process conditions MS2 phage inactivation was found to be more than 8 logs for both MP-UV/H2O2 and LP-UV/H2O2.

에너지 절감형 평형수 처리장치 개발에 관한 연구 (I)

본 논문에서는 에너지 절감형 선박평형수 처리장치 개발을 위한 저압 자외선 램프의 적용에 대하여 연구하였다. 중압 및 저압 자외선 램프의 방사 에너지 분포를 분석하여 램프의 최적배치방안에 대해 제안하였다. 실험결과에 기초하여 저압 자외선 램프로 구성되는 살균 챔버를 제작하였다. 챔버의 정격 전력은 216 [W], 처리용량은 10 [㎥/h]이며, 이는 기존 중압 자외선 램프 2 [㎾] 2개로 처리되는 살균 챔버의 능력을 대처할 수 있다. 살균성능은 중압 자외선 램프에 비해 소비전력은 약 1/18이지만 미생물 94 [%], 동물성 플랑크톤 93 [%], 식물성 플랑크톤 94 [%]로 높게 나타났다.<BR> 따라서, 저압 자외선 램프의 적용으로 100 [㎥/h]이하의 소용량에서는 에너지절감형 선박평형수 처리시스템의 개발이 가능할 것으로 판단된다.

Effect of Host Cells on Low- and Medium-Pressure UV Inactivation of Adenoviruses

UV disinfection is highly effective against most pathogens, with the exception of the adenoviruses (AD). To date, many studies have focused on low-pressure (LP) UV inactivation of AD, but little is known about the effect of medium-pressure (MP) UV inactivation of AD. Despite numerous studies of LP UV inactivation of AD, extreme variabilities in the LP UV dose requirements of AD had been observed because of differing experimental conditions used, such as the types of cell lines used for AD enumeration. This study therefore investigates the effect of three different host cell lines (PLC/PRF/5, human embryonic kidney 293 [HEK293], and XP17BE) on the LP and MP UV dose requirements of AD serotype 5 (AD5), AD40, and AD41 under similar experimental settings. Results showed that for 4-log inactivation of AD, LP UV and MP UV doses needed to be in the ranges of 123 to 182 mJ/cm² and 65 to 90 mJ/cm², respectively, when HEK293 and PLC/PRF/5 cells were used for enumeration. The UV doses required for MP UV inactivation of AD were significantly lower than those required for LP UV inactivation (P value < 0.05). When different cell lines were used for enumeration, UV dose requirements for AD differed. AD were portrayed to be most susceptible to UV (LP UV doses of <57 mJ/cm² and MP UV doses of <42 mJ/cm² for 4-log AD inactivation) when the XP17BE cells were used as the host cell. The use of different cell lines for AD enumeration affected LP UV dose results more significantly than MP UV dose results (P value < 0.05). Cell line variability factors for LP UV disinfection (CL(LP)) and MP UV disinfection (CL(MP)) for AD5, AD40, and AD41 enumerated with HEK293, PLC/PRF/5, and XP17BE cells were in the ranges of 1.0 to 3.2 and 1.0 to 2.5, respectively.

The effect of UV/H2O2 treatment on biofilm formation potential

Greater Cincinnati Water Works (GCWW) evaluated the efficacy of ultraviolet light/hydrogen peroxide advanced oxidation (UV/H2O2) for reducing trace organic contaminants in natural water with varying water qualities. A year-long UV/H2O2 pilot study was conducted to examine a variety of seasonal and granular activated carbon (GAC) breakthrough conditions. The UV pilot-scale reactors were set to consistently achieve 80% atrazine degradation, allowing comparison of low pressure (LP) and medium pressure (MP) lamp technologies for by-product formation. Because hydroxyl radicals react non-selectively with organic compounds, unintended by-product formation occurred.Total assimilable organic carbon (AOC) concentration increased through the reactors from 14 to 33% on average, depending on water quality. Natural organic matter (NOM) contains the precursors for AOC production, so when post-GAC water (versus conventionally treated water) served as reactor influent, less AOC was produced. No appreciable difference in AOC concentration was observed between LP and MP UV reactors. The Spirillum strain NOX fraction of the AOC increased from 50 to 65% on average, depending on the quality of the water. The increase in this fraction of AOC occurred because oxidation of NOM yielded smaller more assimilable organic compounds such as organic acids that are necessary for NOX growth. The Pseudomonas fluorescens strain P17 AOC concentration increased only when conventionally treated plant water was used as pilot influent. This organism thrives in waters of differing organic energy sources, but does not thrive well in carboxylic acids alone. The CONV water had more overall TOC that could contribute to higher P17 AOC counts.Biofilm coupon studies indicated that biofilms with greater heterotrophic plate counts were observed in the granular activated carbon (GAC) effluent streams receiving UV/H2O2 pre-treatment. Biofilm coupon studies additionally indicated that the effluent stream of the GAC column proceeded by the MP reactor exhibited more viable biofilm than the other GAC effluent streams based on an ATP-bioluminescence method. The increased viability of the biofilm produced by the MP UV reactor is likely a result of the multiple UV wavelengths and higher energy input characteristic of this technology.

Reactivation of Giardia lamblia cysts after exposure to polychromatic UV light

In this study, we determined the ability of a promising alternative UV technology--a polychromatic emission from a medium-pressure UV (MP UV) technology--to inhibit the reactivation of UV-irradiated Giardia lamblia cysts. A UV-collimated beam apparatus was used to expose shallow suspensions of purified G. lamblia cysts in PBS (pH 7.2) or filtered drinking water to a low dose (1 mJ cm(-2)) of MP UV irradiation. After UV irradiation, samples were exposed to two repair conditions (light or dark) and two temperature conditions (25 °C or 37 °C for 2-4 h). The inactivation of G. lamblia cysts by MP UV was very extensive, and c. 3 log(10) inactivation was achieved with a dose of 1 mJ cm(-2) . Meanwhile, there was no apparent reactivation (neither in vivo nor in vitro) of UV-irradiated G. lamblia under the conditions tested. The results of this study indicated that, unlike the traditional low-pressure (LP) UV technology, an alternative UV technology (MP UV) could inhibit the reactivation of UV-irradiated G. lamblia cysts even when the cysts were exposed to low UV doses. It appears that alternative UV technology has some advantages over the traditional LP UV technology in drinking water disinfection because of their high level of inactivation against G. lamblia cysts and also effective inhibition of reactivation in UV-irradiated G. lamblia cysts.

Inactivation of human adenovirus by sequential disinfection with an alternative ultraviolet technology and monochloramine

In an effort to reduce human exposure to adenoviruses through drinking water, we determined the effectiveness of sequential disinfection with an alternative ultraviolet (UV) technology (medium-pressure (MP) UV) and monochloramine. The results of this study showed that MP UV was much more effective than traditional UV technology (low-pressure (LP) UV) against human adenovirus 2 (Ad2). Specifically, an inactivation of approximately 3 log10 was achieved by a dose of 40 mJ/cm2 of MP UV compared to ~1 log10 by the same dose of LP UV. However, because of the ineffective inactivation of Ad2 by monochloramine, a very high dose (40 mJ/cm2) of MP UV and a very large Ct99 value (approximately 1200 mg/L.min) was still needed to achieve a significant inactivation (e.g., 4 log10) of Ad2. Also, it appears that the inactivation of Ad2 by monochloramine is not enhanced by prior exposure to MP UV. Overall, the results of this study indicated that, in spite of the enhanced effectiveness of alternative UV technologies on human adenoviruses, sequential disinfection with an alternative UV technology (MP UV) and monochloramine still may not provide adequate inactivation of human adenoviruses - especially at high pH and low temperature - in drinking water treatment processes.

Pilot-scale studies of combined clarification, filtration, and ultraviolet radiation systems for disinfection of secondary municipal wastewater effluent

Disinfection of municipal wastewater effluent was evaluated using three alternatives, including: (1) low-pressure (LP) + medium-pressure (MP) UV lamps; (2) clarifier + LP + MP; and (3) pressurized sand filter + LP + MP. Total coliform (TC), fecal coliform (FC), fecal Streptococcus (FS), TSS, several physicochemical parameters, absorbtivity and UV transmittance (UVT; %) were tested. The UVT% for secondary, clarified and filtered effluents were 3.5, 34 and 50, respectively. A 15% photo-reactivation in secondary effluent disinfected by LP lamp was observed, while it was limited to 0.03% by the MP lamp after filtration. Filtration to a surface overflow rate (SOR) of 1050 L/m 2 h, followed by MP irradiation at a dose of 230 mW s/cm 2 was an effective alternative to reduce the TC, FC, and FS in the disinfected secondary effluent. Filtration + MP lamp met the standards of 1000 TC and 400 FC/100 mL for effluent discharge to receiving waters. This process can also inactivate FS, effecting a 6-log reduction. Among the evaluated alternatives, none of the other treatment systems performed as well as the pressurized sand filter + MP lamp, making this the best combination for post-treatment and disinfection of secondary effluent from a well-run wastewater treatment plant.

UV/H 2O 2 treatment of drinking water increases post-chlorination DBP formation

Ultraviolet (UV) irradiation has become popular as a primary disinfectant because it is very effective against Cryptosporidium and does not directly form regulated disinfection by-products. Higher UV doses and UV advanced oxidation (UV/H 2O 2) processes are under consideration for the treatment of trace organic pollutants (e.g. pharmaceuticals, personal care products). Despite the disinfection effectiveness of UV light, a secondary disinfectant capable of maintaining a distribution system residual is required to meet current U.S. regulation. This study investigated changes in disinfection by-product (DBP) formation attributed to UV or UV/H 2O 2 followed by application of free chlorine to quench hydrogen peroxide and provide residual disinfectant. At a UV dose of 1000 mJ/cm 2, trihalomethane (THM) yield increased by up to 4 μg/mg-C and 13 μg/mg-C when treated with low and medium pressure UV, respectively. With the addition of hydrogen peroxide, THM yield increased by up to 25 μg/mg-C (5 mg-H 2O 2/L) and 37 μg/mg-C (10 mg-H 2O 2/L). Although no changes in DBPs are expected during UV disinfection, application of UV advanced oxidation followed by chlorine addition was assessed with regard to impacts on DBP formation.

Evaluation of water treatment plant UV reactor efficiency against Cryptosporidium parvum oocyst infectivity in immunocompetent suckling mice

To assess the efficiency of a medium-pressure UV reactor under full-scale water treatment plant (WTP) conditions on the infectivity of Cryptosporidium parvum oocysts in an Naval Medical Research Institute (NMRI) suckling mice infectivity model. Six/seven-day-old mice were administered orally 2-10x10(4)Cryptosporidium parvum oocysts. Compared with nonirradiated oocysts, 40 mJ cm(-2) UV irradiation of ingested oocysts resulted 7 days later in a 3.4-4.0 log10 reduction in the counts of small intestine oocysts, using a fluorescent flow cytometry assay. Present data extend to industrial conditions previous observations of the efficiency of UV irradiation against Cryptosporidium parvum oocyst in vivo development. Present results suggest that in WTP conditions, a medium-pressure UV reactor is efficient in reducing the infectivity of Cryptosporidium parvum oocysts, one of the most resistant micro-organisms present in environmental waters.

Effects of bromide on UV/chlorine advanced oxidation process

High quantum yield (1.4 mol Es−1) of hydroxyl radicals (∙OH) from photolysis of chlorine under typical disinfection conditions indicates the potential of UV/chlorine coexposure in serving as both disinfection and advanced oxidation processes (AOP). In this study, photolysis of chlorine and bromine was explored in buffer and simulated natural water solutions under low-pressure UV (LPUV) and medium-pressure UV (MPUV) lamps. At pH 6.5 and 8.5, the quantum yields of bromine photolysis were 3.8 and 0.6 for MPUV, and 4.4 and 0.8 for LPUV, respectively. At pH 6.5, the photolysis of bromine was faster than that of chlorine under either MPUV or LPUV source, while at a higher pH of 8.5, the contrary was found. For all conditions tested, the presence of bromide did not significantly change the observed photolysis rate of total free halogen during the UV/chlorine process in the presence or absence of natural organic matter. Upon UV irradiation, chlorine always produces higher ∙OH concentration than bromine does. The presence of bromide results in considerable decrease of ∙OH concentration at pH 6.5, compared to that obtained from the UV/chlorine process in the absence of bromide.

PH induced polychromatic UV treatment for the removal of a mixture of SMX, OTC and CIP from water

Water and wastewater effluents contain a vast range of chemicals in mixtures that have different chemical structures and characteristics. This study presents a treatment technology for the removal of mixtures of antibiotic residues (sulfamethoxazole (SMX), oxytetracycline (OTC) and ciprofloxacin (CIP)) from contaminated water. The treatment combines pH modification of the water to an optimal value, followed by a photolytic treatment using direct polychromatic ultraviolet (UV) irradiation by medium pressure UV lamp. The pH adjustment of the treated water leads to structural modifications of the pollutant's molecule thus may enhance direct photolysis by UV light. Results showed that an increase of water pH from 5 to 7 leads to a decrease in degradation rate of SMX and an increase in degradation rate of OTC and CIP, when studied separately and not in a mixture. Thus, the optimal pH values for UV photodegradation in a mixture, involve initial photolysis at pH 5 and then gradually changing the pH from 5 to 7 during the UV exposure. For example, this resulted in 99% degradation of SMX at pH 5 and enhanced degradation of OTC and CIP from 54% and 26% to 91% and 96% respectively when pH was increased from 5 to 7. Thus the pH induced photolytic treatment has a potential in improving treatment of antibiotics in mixtures.

Inactivation of environmental mycobacteria by free chlorine and UV

The resistance of environmental mycobacteria (EM) against chlorine and ultraviolet (UV) was evaluated for determination of the Ct value and UV dose to inactivate EM. Chlorine disinfection experiments were done on Mycobacterium fortuitum in oxidant demand-free buffered water at the worst condition (pH 8.5, 4 °C) and normal condition (pH 7.0, 20 °C). The Ct value for 3 log inactivation of M. fortuitum was 600 times greater than that of Escherichia coli. UV experiments were performed for various species of Mycobacterium avium, M. fortuitum, Mycobacterium intracellulare, and Mycobacterium lentiflavum. A UV collimated beam device was used for irradiation of four species suspended in phosphate buffered saline with doses of 5, 10, 20, 50, and 100 mJ/cm 2. UV sensitivity of mycobacteria was species-specific. More than 3 log of M. avium, M. intracellulare, and M. lentiflavum could be inactivated at 20 mJ/cm 2, whereas M. fortuitum was so resistant that 3 log inactivation required a dose of more than 50 mJ/cm 2. Mycobacteria were found 2–10 times more resistant to UV than E. coli for 3 log inactivation. There was no significant difference in the inactivation of mycobacteria with either low-pressure or medium-pressure UV irradiation.

Anatoxin-a degradation by Advanced Oxidation Processes: Vacuum-UV at 172 nm, photolysis using medium pressure UV and UV/H2O2

Two Advanced Oxidation Processes, namely vacuum-ultraviolet (VUV) photolysis at 172nm and ultraviolet/hydrogen peroxide (UV/H2O2) were investigated for the degradation of anatoxin-a in aqueous solutions. Solutions of anatoxin-a-fumarate were treated with VUV light at 172nm with a UV dose of 200 mJ/cm2, where fumaric acid served as a reference compound for a competition kinetics analysis. The second-order rate constant for the reaction between anatoxin-a and the hydroxyl radical was found to be (5.2±0.3)×109M−1 s−1 and was independent of pH, temperature, and initial concentration of anatoxin-a. The direct photolysis of anatoxin-a using a medium pressure (MP) UV lamp was also investigated, in which case a UV dose of 1285 mJ/cm2 was required to degrade anatoxin-a by 88% and 50% at concentrations of 0.6mg/L and 1.8mg/L of toxin, respectively. Treatment of anatoxin-a with a low pressure (LP) UV lamp in the presence of 30mg/L of H2O2 was examined, where it was found that more than 70% of toxin could be degraded at a UV dose of 200 mJ/cm2. The degradation arises from the oxidation of the toxin by hydroxyl radicals. The addition of H2O2 clearly enhanced the degradation of anatoxin-a, up to a concentration of 40mg/L, after which addition of more H2O2 had little effect on the degradation kinetics of anatoxin-a. The effect of background constituents in the water on the degradation of anatoxin-a was also investigated using natural and synthetically produced model waters.

Enhanced effectiveness of medium-pressure ultraviolet lamps on human adenovirus 2 and its possible mechanism

There has been growing concern over human exposure to adenoviruses through drinking water due to their apparent high resistance to UV irradiation and the anticipated widespread use of ultraviolet (UV) disinfection in drinking water treatment processes. However, most inactivation studies on adenoviruses were performed using only one type of UV technology--low-pressure (LP) UV, and little is known about the effectiveness of different UV technologies such as medium- pressure (MP) UV or other polychromatic UV technologies. In this work, the kinetics and extent of inactivation of a human adenovirus (adenovirus 2 (Ad2)) by both monochromatic LP and polychromatic MP UV were evaluated to determine the effectiveness of these UV technologies on human adenoviruses. Inactivation of Ad2 by LP UV was very slow and only 0.87 and 2.17 log(10) inactivation was achieved with UV doses of 30 and 90 mJ/cm(2), respectively. However, inactivation of Ad2 by MP UV was much faster and 2.19 and 5.36 log(10) inactivation was observed with the same UV doses (30 and 90 mJ/cm(2), respectively). It appears that MP UV is more effective against Ad2 than LP UV and the enhanced effectiveness of MP UV on Ad2 is likely due to its ability to inhibit the repair process in UV-irradiated Ad2.

Demonstrating 4‐log adenovirus inactivation in a medium‐pressure UV disinfection reactor

Previous bench‐scale results demonstrated that polychromatic medium‐pressure (MP) ultraviolet (UV) disinfection could achieve 4‐log adenovirus inactivation at equivalent UV doses well below those required under the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). These findings were confirmed and extended to a full‐scale UV disinfection reactor using a live adenovirus challenge. The MP UV disinfection system was able to measure &gt; 4‐log adenovirus disinfection at an MS2 coliphage reduction equivalent dose (RED) of &lt; 100 mJ/cm2. The highest observed adenovirus‐based RED achieved, referenced to a low‐pressure (LP) UV dose‐response, was 233 mJ/cm2; the validated RED, including relevant validation factors, was equivalent to that required by the LT2ESWTR for 4‐log virus inactivation credit. These results proved that required virus disinfection doses can be validated and that MP UV is capable of meeting the 4‐log virus disinfection standard in the LT2ESWTR at a measurable and achievable UV dose substantially lower than that of LP UV technology.