Previous laboratory scale studies indicate nanofiltration (NF) and UV-sulfite photochemical treatments as promising technologies for the removal and destruction, respectively, of per- and polyfluoroalkyl substances (PFASs) from contaminated water. This study reports on a field demonstration of a pilot-scale hybrid NF and UVsulfite treatment train for the remediation of 12 PFASs detected in groundwater impacted by aqueous filmforming foam (AFFF) at a U.S. Department of Defense installation. For most of the detected PFASs, NF rejection was consistently >= 95% over a 30-day field trial when operating at 90% total permeate recovery. Rejection of short-chain perfluorosulfonic acids (PFSAs) by NF decreased when recoveries increased from 90 to 97%; tests with a reverse osmosis (RO) membrane showed >= 99% rejection of all PFASs regardless of increasing recovery. UV treatment of the NF reject following 90% permeate recovery resulted in variable destruction of individual PFASs, with rates also being dependent on pH and the identity and concentration of UV photosensitizer. Rates of perfluorocarboxylic acid (PFCA) degradation were greater than those measured for PFSAs and perfluoroalkyl acid (PFAA) precursors and were independent of perfluoroalkyl chain length. In contrast, rates of PFSA degradation increased with increasing chain length. Consistent levels of PFAS degradation by UV-sulfite were observed during a 30-day demonstration experiment in NF reject water amended with 10 mM sulfite and adjusted to pH 11.2. Collectively, > 75% of the detected PFAS mass in the NF reject was destroyed after 4 h of UV treatment, increasing to > 90% after 8 h of treatment. An analysis of electrical energy inputs for the hybrid NF/UV-sulfite treatment train showed energy per order magnitude (EE/O) requirements ranging from <= 13.1 kWh/m3 for PFCAs and 14.1 kWh/m(3) for PFOS to values > 100 kWh/m(3) for more recalcitrant short-chain PFSA analogues. The UV reactor and water-cooling system were the major contributors to overall energy requirements and represent the greatest opportunities for improving efficiency of the technology.

Many installed UV systems operate inefficiently over time, which increases operation and maintenance (O&M) costs and can lead to microbial permit violations. A WateReuse Research Foundation (WRRF) project titled “UV Disinfection Knowledgebase for Reuse Applications” is evaluating these issues. The objectives of this project were to benchmark the performance of UV systems used in reuse applications, develop recommendations for UV implementation for nonand direct potable reuse, and develop troubleshooting tools that utilities can use to quantify and optimize UV system operation. Lessons learned from conversations with operators along with data collected during the UV system performance audits provides good recommendations for better UV implementation.

Ultraviolet (UV) reactors used for disinfecting water and wastewater must be validated and monitored over time. The validation process requires understanding the photochemical properties of the pathogens of concern and the challenge microorganisms used to represent them. Specifically for polychromatic UV systems, the organisms' dose responses to UV light and their sensitivity across the UV spectrum must be known. This research measured the UV spectral sensitivity, called action spectra, of Cryptosporidium parvum, and MS2, T1UV, Q Beta, T7, and T7m Coliphages, as well as Bacillus pumilus spores. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths at 10 nm intervals between 210 and 290 nm. Above 240 nm, all bacteria and viruses tested exhibited a relative peak sensitivity between 260 and 270 nm. Of the coliphage, MS2 exhibited the highest relative sensitivity below 240 nm, relative to its sensitivity at 254 nm, followed by Q Beta, T1UV, T7m and T7 coliphage. B. pumilus spores were more sensitive to UV light at 220 nm than any of the coliphage. These spectra are required for calculating action spectra correction factors for medium pressure UV system validation, for matching appropriate challenge microorganisms to pathogens, and for improving UV dose monitoring. Additionally, understanding the dose response of these organisms at multiple wavelengths can improve polychromatic UV dose calculations and enable prediction of pathogen inactivation from wavelength-specific disinfection technologies such as UV light emitting diodes (LEDs).

The use of bioassays to determine reduction equivalent doses delivered by UV reactors is recognized as an effective measure of UV disinfection systems. Low pressure (LP) UV delivered in controlled collimated beam systems provides dose response curves which are then compared against reactor performance to quantify the delivered dose. It is recognized that the appropriateness of monochromatic LP dose curves for validating polychromatic medium pressure depends on knowledge of the action spectra of the bioassay surrogate and the target pathogen. Further complicating the relationship between reduction equivalent doses (RED) generated during validation and effective dose delivered by a medium pressure UV system at an installation is the absorbance spectrum of the validation water versus that at the utility. Other factors that affect the dependability of bioassay results for medium pressure systems include quartz sleeve absorbance spectra and lamp spectral output. These latter factors can be resolved or corrected for, but not without knowledge of the action spectra of the microorganisms in question.

Ultraviolet (UV) disinfection relies on the principal that DNA exposure to UV irradiation leads to the formation of cytotoxic lesions resulting in the inactivation of microorganisms. Cyclobutane pyrimdine dimers (CPDs) account for the majority of DNA lesions upon UV exposure. Past research has demonstrated reversal of CPDs in extracted DNA formed at high UV-C wavelength irradiation (280 nm) upon subsequent irradiation at lower UVC wavelengths (230-240 nm). Medium-pressure (MP) UV lamps produce a polychromatic emission giving rise to the possibility that cellular DNA in a target pathogen may undergo simultaneous damage and repair when exposed to multiple wavelengths during the disinfection process, decreasing the efficiency of MP UV lamp disinfection. Culture techniques and a quantitative polymerase chain reaction (qPCR) assay were used to examine cell viability and DNA damage reversal. qPCR results indicated direct photoreversal of UV-induced DNA damage through sequential irradiations of 280 nm followed by 228 nm in Escherichia coli DNA. However, significant photoreversal was only observed after high initial doses and secondary doses of UV light. The doses where significant photoreversal took place were more than 10 times higher than those typically used in UV disinfection. Despite evidence of CPD photoreversal, bacterial growth assays showed no indication that sequential-wavelength irradiations result in higher survival rates than single-wavelength irradiations. (C) 2014 Elsevier Ltd. All rights reserved.

The emittance of new and aged amalgam low-pressure lamps used by a drinking water ultraviolet (UV) disinfection reactor was measured along the length and about the circumference. The new lamp had a non-uniform emittance along the length of the lamp with local maxima between the electrodes and the amalgam deposits. The aged lamps showed a reduction in emittance and a non-uniform output both along the length and about the circumference. The reduction and non-uniformity increased with lamp age and were most notable at the lamp ends, and the position of the maximum emittance moves to the lamp centre. Computer simulations of the UV reactor show that the position of the UV sensor that indicates UV dose delivery is crucial. The UV dose will be overpredicted if the UV sensor views a location that ages the least but underpredicted if the UV sensor views a location that ages the most.

Adenovirus is regarded as the most resistant pathogen to ultraviolet (UV) disinfection due to its demonstrated resistance to monochromatic, low-pressure (LP) UV irradiation at 254 nm. This resistance has resulted in high UV dose requirements for all viruses in regulations set by the United States Environmental Protection Agency. Polychromatic, medium-pressure (MP) UV irradiation has been shown to be much more effective than 254 nm, although the mechanisms of polychromatic UV inactivation are not completely understood. This research analyzes the wavelength-specific effects of UV light on adenovirus type 2 by analyzing in parallel the reduction in viral infectivity and damage to the viral genome. A tunable laser from the National Institute of Standards and Technology was used to isolate single UV wavelengths. Cell culture infectivity and PCR were employed to quantify the adenoviral inactivation rates using narrow bands of irradiation (<1 nm) at 10 nm intervals between 210 and 290 nm. The inactivation rate corresponding to adenoviral genome damage matched the inactivation rate of adenovirus infectivity at 253.7 nm, 270 nm, 280 nm, and 290 nm, suggesting that damage to the viral DNA was primarily responsible for loss of infectivity at those wavelengths. At 260 nm, more damage to the nucleic acid was observed than reduction in viral infectivity. At 240 nm and below, the reduction of viral infectivity was significantly greater than the reduction of DNA amplification, suggesting that UV damage to a viral component other than DNA contributed to the loss of infectivity at those wavelengths. Inactivation rates were used to develop a detailed spectral sensitivity or action spectrum of adenovirus 2. This research has significant implications for the water treatment industry with regard to polychromatic inactivation of viruses and the development of novel wavelength-specific UV disinfection technologies.

Three-dimensional laser-induced fluorescence (3DLIF) was applied to visualize and quantitatively analyze mixing in a lab-scale UV reactor consisting of one lamp sleeve placed perpendicular to flow. The recirculation zone and the von Karman vortex shedding that commonly occur in flows around bluff bodies were successfully visualized. Multiple flow paths were analyzed by injecting the dye at various heights with respect to the lamp sleeve. A major difference in these pathways was the amount of dye that traveled close to the sleeve, i.e., a zone of higher residence time and higher UV exposure. Paths away from the center height had higher velocities and hence minimal influence by the presence of sleeve. Approach length was also characterized in order to increase the probability of microbes entering the region around the UV lamp. The 3DLIF technique developed in this study is expected to provide new insight on UV dose delivery useful for the design and optimization of UV reactors.

INTRODUCTION The UV Disinfection Guidance Manual (UVDGM) provides test protocols for validating dose delivery and monitoring by UV reactors. Validation involves measuring the dose delivery of the UV reactor under various test conditions of flow, water UV transmittance, and lamp output, and verifying the ability of the reactors monitoring system to indicate that dose delivery. The test conditions should span the operating range of these variables expected at the water treatment plant (WTP) where the reactor will be installed (USEPA, 2003).