Accelerated Ultraviolet Treatment of Carbamazepine and NDMA in Water under 222 nm Irradiation.

Krypton chloride (KrCl*) excimer ultraviolet (UV) light may provide advantages for contaminant degradation compared to conventional low-pressure (LP) UV. Direct and indirect photolysis as well as UV/hydrogen peroxide-driven advanced oxidation (AOP) of two chemical contaminants were investigated in laboratory grade water (LGW) and treated secondary effluent (SE) for LPUV and filtered KrCl* excimer lamps emitting at 254 and 222 nm, respectively. Carbamazepine (CBZ) and N-nitrosodimethylamine (NDMA) were chosen because of their unique molar absorption coefficient profiles, quantum yields (QYs) at 254 nm, and reaction rate constants with hydroxyl radical. Quantum yields and molar absorption coefficients at 222 nm for both CBZ and NDMA were determined, with measured molar absorption coefficients of 26 422 and 8170 M-1 cm-1, respectively, and QYs of 1.95 × 10-2 and 6.68 × 10-1 mol Einstein-1, respectively. The 222 nm irradiation of CBZ in SE improved degradation compared to that in LGW, likely through promotion of in situ radical formation. AOP conditions improved degradation of CBZ in LGW for both UV LP and KrCl* sources but did not improve NDMA decay. In SE, photolysis of CBZ resulted in decay similar to that of AOP, likely due to the in situ generation of radicals. Overall, the KrCl* 222 nm source significantly improves contaminant degradation compared to that of 254 nm LPUV.

Rapid Inactivation of Fungal Spores in Drinking Water by Far-UVC Photolysis of Free Chlorine.

Effective and affordable disinfection technology is one key to achieving Sustainable Development Goal 6. In this work, we develop a process by integrating Far-UVC irradiation at 222 nm with free chlorine (UV222/chlorine) for rapid inactivation of the chlorine-resistant and opportunistic Aspergillus niger spores in drinking water. The UV222/chlorine process achieves a 5.0-log inactivation of the A. niger spores at a chlorine dosage of 3.0 mg L-1 and a UV fluence of 30 mJ cm-2 in deionized water, tap water, and surface water. The inactivation rate constant of the spores by the UV222/chlorine process is 0.55 min-1, which is 4.6-fold, 5.5-fold, and 1.8-fold, respectively, higher than those of the UV222 alone, chlorination alone, and the conventional UV254/chlorine process under comparable conditions. The more efficient inactivation by the UV222/chlorine process is mainly attributed to the enhanced generation of reactive chlorine species (e.g., 6.7 × 10-15 M of Cl•) instead of hydroxyl radicals from UV222 photolysis of chlorine, which is verified through both experiments and a kinetic model. We further demonstrate that UV222 photolysis damages the membrane integrity and benefits the penetration of chlorine and radicals into cells for inactivation. The merits of the UV222/chlorine process over the UV254/chlorine process also include the more effective inhibition of the photoreactivation of the spores after disinfection and the lower formation of chlorinated disinfection byproducts and toxicity.

Improving the Reliability of Water Service Delivery in Rural Kenya through Professionalized Maintenance: A System Dynamics Perspective.

Reliable water service delivery continues to be a complex global issue that is particularly challenging in rural communities. Despite billions of dollars of infrastructure interventions, sustainable water services remain out of reach for millions of people. Professionalized maintenance services have emerged as a service provision strategy to supplement the community-based rural water management approach. This study applies system dynamics modeling to assess the potential impact of scaling up professionalized maintenance services on piped water systems in Kitui County, Kenya. The study results show that over a 10 year simulation, calibrated with 21 months of empirical data and based on a range of key assumptions, delivery of professionalized maintenance services across the county may increase countywide functionality rates from 54% to over 83%, leading to a 67% increase in water production. Furthermore, the increase in preventive maintenance activities and proactive repairs can lead to less frequent major breakdowns and reduction in county government spending on major repairs by over 60%. However, current service fee income from communities accounts for 8% of the total cost of service, necessitating substantial sustained external financing or government subsidies to be financially viable at scale.

Field study of early implementation of UV sources and their relative effectiveness for public health and safety.

The emergence of COVID-19 and its corresponding public health burden has prompted industries to rapidly implement traditional and novel control strategies to mitigate the likelihood of SARS-CoV-2 transmission, generating a surge of interest and application of ultraviolet germicidal irradiation (UVGI) sources as disinfection systems. With this increased attention the need to evaluate the efficacy and safety of these types of devices is paramount. A field study of the early implementation of UVGI devices was conducted at the Space Needle located in Seattle, Washington. Six devices were evaluated, including four low-pressure (LP) mercury-vapor lamp devices for air and surface sanitation not designed for human exposure and two krypton chloride (KrCl*) excimer lamp devices to be operated on and around humans. Emission spectra and ultraviolet (UV) irradiance at different locations from the UV devices were measured and germicidal effectiveness against SARS-CoV-2 was estimated. The human safety of KrCl* excimer devices was also evaluated based on measured irradiance and estimated exposure durations. Our results show all LP devices emitted UV radiation primarily at 254 nm as expected. Both KrCl* excimers emitted far UVC irradiation at 222 nm as advertised but also emitted at longer, more hazardous wavelengths (228 to 262 nm). All LP devices emitted strong UVC irradiance, which was estimated to achieve three log reduction of SARS-CoV-2 within 10 sec of exposure at reasonable working distances. KrCl* excimers, however, emitted much lower irradiance than needed for effective disinfection of SARS-CoV-2 (>90% inactivation) within the typical exposure times. UV fluence from KrCl* excimer devices for employees was below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs) under the reported device usage and work shifts. However, photosensitive individuals, human susceptibility, or exposure to multiple UV sources throughout a worker's day, were not accounted for in this study. Caution should be used when determining the acceptability of UV exposure to workers in this occupational setting and future work should focus on UVGI sources in public settings.

UV Inactivation of SARS-CoV-2 across the UVC Spectrum: KrCl* Excimer, Mercury-Vapor, and Light-Emitting-Diode (LED) Sources.

Effective disinfection technology to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can help reduce viral transmission during the ongoing COVID-19 global pandemic and in the future. UV devices emitting UVC irradiation (200 to 280 nm) have proven to be effective for virus disinfection, but limited information is available for SARS-CoV-2 due to the safety requirements of testing, which is limited to biosafety level 3 (BSL3) laboratories. In this study, inactivation of SARS-CoV-2 in thin-film buffered aqueous solution (pH 7.4) was determined across UVC irradiation wavelengths of 222 to 282 nm from krypton chloride (KrCl*) excimers, a low-pressure mercury-vapor lamp, and two UVC light-emitting diodes. Our results show that all tested UVC devices can effectively inactivate SARS-CoV-2, among which the KrCl* excimer had the best disinfection performance (i.e., highest inactivation rate). The inactivation rate constants of SARS-CoV-2 across wavelengths are similar to those for murine hepatitis virus (MHV) from our previous investigation, suggesting that MHV can serve as a reliable surrogate of SARS-CoV-2 with a lower BSL requirement (BSL2) during UV disinfection tests. This study provides fundamental information on UVC's action on SARS-CoV-2 and guidance for achieving reliable disinfection performance with UVC devices. IMPORTANCE UV light is an effective tool to help stem the spread of respiratory viruses and protect public health in commercial, public, transportation, and health care settings. For effective use of UV, there is a need to determine the efficiency of different UV wavelengths in killing pathogens, specifically SARS-CoV-2, to support efforts to control the ongoing COVID-19 global pandemic and future coronavirus-caused respiratory virus pandemics. We found that SARS-CoV-2 can be inactivated effectively using a broad range of UVC wavelengths, and 222 nm provided the best disinfection performance. Interestingly, 222-nm irradiation has been found to be safe for human exposure up to thresholds that are beyond those effective for inactivating viruses. Therefore, applying UV light from KrCl* excimers in public spaces can effectively help reduce viral aerosol or surface-based transmissions.

Household Water, Sanitation, and Hygiene Practices Impact Pathogen Exposure in Remote, Rural, Unpiped Communities.

Household water, sanitation and hygiene (WASH) practices in remote, rural, and unpiped communities are likely to impact exposure to pathogens beyond the fecal-oral transmission routes that are typically prioritized in WASH interventions. We studied 43 homes in two remote, rural, unpiped communities in Alaska to evaluate seasonal water haul, water sources, water quality, and water reuse, as well as greywater and human waste disposal over 1 year. Hauled quantities of water reportedly ranged from 3.0 to 5.4 gallons per capita per day (gpcd) depending on the community and season. Natural, untreated water sources contributed 0.5-1.1 gpcd to household water availability. Reported quantities of water hauled were significantly correlated with total water storage capacity in the home. Total coliforms were detected in 30-60% of stored household water samples from treated and untreated sources, and total coliform counts were significantly higher in specific sources and during specific seasons. Exposure to pathogens during periods of low water access, from untreated water reuse, from greywater disposal and from human waste disposal are important pathways of disease transmission in these remote, rural, unpiped communities. We discuss intermediate steps that can be taken at the household and community levels to interrupt exposure pathways before piped infrastructure is installed. This model of examining specific household practices to determine transmission routes can be applied to other remote communities or unique conditions to aid in the recommendation of targeted WASH interventions.

Thinking Outside the Treatment Plant: UV for Water Distribution System Disinfection.

This work critically evaluates the current paradigm of water distribution system management and juxtaposes that with the potential benefits of employing UV irradiation, which we hope will catalyze a judicial re-evaluation of the current practices in water distribution system management and spur critical research and a new way of thinking about secondary disinfection across the extent of distribution systems. Given the recent advances in UV technology and the efficacy of UV disinfection against all pathogen classes, we now see UV applications for disinfection in many aspects of consumers lives: in water coolers, dishwashers, coffee makers, and disinfection of personal items like gym bags, water bottles, and toothbrushes. Public and regulatory concern over water quality and pathogens, especially the recent interest in building plumbing, calls out for new approaches to disinfection and distribution system management. We envision a new model for secondary disinfection in water distribution systems utilizing emerging germicidal UV LED-based disinfection. UV irradiation in water treatment can achieve high levels of disinfection of all pathogens and minimize or eliminate the formation of regulated disinfection byproducts. So why is UV not considered as a secondary disinfectant for distribution systems? In this Account, we lay out the logic as to the benefits and practicality of adding distributed UV treatment to assist in protection of distribution systems and protect water quality for human exposure. The possible locations of UV irradiation in distribution systems are envisioned, potentially including UV booster stations along the distribution network, UV in storage tanks or their inlet/outlets, LEDs distributed along pipe walls, small point of use/entry treatment systems for buildings/homes/taps, or submersible swimming or rolling UV LED drones to reach problem pipes and provide a "shock" treatment or provide sterilization after main breaks or repairs. The benefits of UV applications in water also include high effectiveness against chlorine-resistant protozoa, no added disinfection byproducts, and compatibility of adding of UV to existing secondary disinfection strategies for enhanced protection. Potential challenges and research needs are described, such as use of UV-compatible pipe materials, implementation of sensors to monitor distributed LEDs, management of waste heat from the rear surface of the LED, and understanding the potential for regrowth of opportunistic microorganisms. Another notable challenge is the relatively stagnant regulatory environment in some countries to develop frameworks for evaluation and acceptance of UV technology in distribution systems that require a chemical secondary disinfectant. Rapid advances in UV LED research has propelled the growth of this field, but needs still remain, including understanding behavior of biofilms in pipes under UV irradiation, including any beneficial effects that may be lost, the potential for fouling of LED emission surfaces and monitoring points, and provision of a distributed power network to run the LEDs. Regulators may want specific monitoring approaches and advances in real-time monitoring of microbial viability, and engineers may need to develop new approaches to overall management.

Standardization of a UV LED Peak Wavelength, Emission Spectrum, and Irradiance Measurement and Comparison Protocol.

Standard protocols for the measurement of irradiance, peak wavelength, and emission spectra have not yet been established for UV LED devices. This lack of standardization creates an uneven field for comparison between products. A detailed protocol was developed and tested in 14 facilities spanning manufacturers of UV LEDs and devices and research institutions in seven different countries. This protocol includes equipment calibration specifications, methods for the measurement and comparison calculations of irradiance and emission spectra, methods for the determination of peak wavelength, quality control and quality assurance steps, and industry-wide tolerances to error for each type of measurement. Measurements of the same source by operators using different equipment resulted in 2-10× the error found when measurement equipment provided as part of the study was used by each participant. The data were used to identify outliers, determine prediction intervals, and define acceptable tolerances to error. With this protocol, manufacturers have a means to report their UV LED specifications with verifiable quality control and quality assurance steps. The protocol and data generated from this study will create more confidence in the industry and standardize the comparison of UV LEDs by consumers, researchers, designers, and regulators.

Rainwater catchments in rural Alaska have the potential to produce high-quality water and high quantities of water for household use.

Rainwater collection is a common source of household water in developed and developing communities where treated on-site water is not available. Although rainwater catchment has been practiced for generations in rural Alaska communities, there are little data available on the quality and quantity of rainwater resources. Forty-eight rainwater samples were collected from nine communities in Alaska over 2 years. Samples were tested for physical water quality parameters, metals, and bacteria. Characteristics of household catchments were recorded. Rainwater quantity in two communities was evaluated. Overall, high-quality water was observed in rain catchments, with average total organic carbon (TOC) and turbidity being lower than or equal to those values in other published rainwater studies. pH was consistently low. Over 80% of samples were below the United States limits for metals and met international microbiological water quality standards. However, variation was observed between households, communities, indoor/outdoor bacteria samples, covered/uncovered storage containers, and over time. The quantity of rainwater available for catchment could supply 17-40% of annual household water and is projected to increase in future decades according to Alaska climate models. Best practices are recommended for rural Alaska communities to maintain the naturally high quality of rainwater and take advantage of large quantities of rainwater available on-site.

Identification of Proprietary Amino Ethoxylates in Hydraulic Fracturing Wastewater Using Liquid Chromatography/Time-of-Flight Mass Spectrometry with Solid-Phase Extraction.

This work describes the discovery of amino-poly(ethylene glycol)s, amino-poly(ethylene glycol) carboxylates, and amino-poly(ethylene glycol) amines in 20 produced water samples from hydraulic fracturing in the western United States. These compounds, with masses in the range of m/ z 120-986, were identified using solid-phase extraction and liquid chromatography/quadrupole time-of-flight mass spectrometry. The polymeric sorbent, Oasis HLB, gave good recovery for all three ethoxylated surfactants and desalted the samples, which significantly reduced suppression of the mass spectral signal allowing detection and identification. The Kendrick mass defect, mass spectra, fragmentation pathways, and pure standards were used for confirmation. Finally, because these compounds are not explicitly listed in FracFocus reports, rather they are categorized as a proprietary surfactant blend; their identification is an important step in understanding the chemistry, treatment, and possible toxicity of hydraulic fracturing wastewater.

Wavelength-Dependent Damage to Adenoviral Proteins Across the Germicidal UV Spectrum.

Adenovirus, a waterborne pathogen responsible for causing bronchitis, pneumonia, and gastrointestinal infections, is highly resistant to UV disinfection and therefore drives the virus disinfection regulations set by the U.S. Environmental Protection Agency. Polychromatic UV irradiation has been shown to be more effective at inactivating adenovirus and other viruses than traditional monochromatic irradiation emitted at 254 nm; the enhanced efficacy has been attributed to UV-induced damage to viral proteins. This research shows UV-induced damage to adenoviral proteins across the germicidal UV spectrum at wavelength intervals between 200 and 300 nm. A deuterium lamp with bandpass filters and UV light-emitting diodes (UV LEDs) isolated wavelengths in approximate 10 nm intervals. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and image densitometry were used to detect signatures for the hexon, penton, fiber, minor capsid, and core proteins. The greatest loss of protein signature, indicating damage to viral proteins, occurred below 240 nm. Hexon and penton proteins exposed to a dose of 28 mJ/cm2 emitted at 214 nm were approximately 4 times as sensitive and fiber proteins approximately 3 times as sensitive as those exposed to a dose of 50 mJ/cm2 emitted at 254 nm. At 220 nm, a dose of 38 mJ/cm2 reduced the hexon and penton protein quantities to approximately 33% and 31% of the original amounts, respectively. In contrast, a much higher dose of 400 mJ/cm2 emitted at 261 and 278 nm reduced the original protein quantity to between 66-89% and 80-93%, respectively. No significant damage was seen with a dose of 400 mJ/cm2 at 254 nm. This research directly correlates enhanced inactivation at low wavelengths with adenoviral protein damage at those wavelengths, adding fundamental insight into the mechanisms of inactivation of polychromatic germicidal UV irradiation for improving UV water disinfection.

Life Cycle Environmental Impacts of Disinfection Technologies Used in Small Drinking Water Systems.

Small drinking water systems serve a fifth of the U.S. population and rely heavily on disinfection. While chlorine disinfection is common, there is interest in minimizing chemical addition, especially due to carcinogenic disinfection byproducts and chlorine-resistant pathogens, by using ultraviolet technologies; however, the relative, broader environmental impacts of these technologies are not well established, especially in the context of small (<10 000 people) water systems. The objective of this study was to identify environmental trade-offs between chlorine and ultraviolet disinfection via comparative life cycle assessment. The functional unit was the production of 1 m3 of drinking water to U.S. STANDARDS: Treatment included cartridge filtration followed by either chlorine disinfection or ultraviolet disinfection with chlorine residual addition. Environmental performance was evaluated for various chlorine contact zone materials (plastic, concrete, steel), ultraviolet validation factors (1.2 to 4.4), and electricity sources (renewable; U.S. average, high, and low impact grids). Performance was also evaluated when filtration and chlorine residual were not required. From a life cycle assessment perspective, replacing chlorine with UV was preferred only in a limited number of cases (i.e., high pumping pressure but filtration is not required). In all others, chlorine was environmentally preferred, although some contact zone materials and energy sources had an impact on the comparison. Utilities can use these data to inform their disinfection technology selection and operation to minimize environmental and human health impacts.

Fecal sludge as a fuel: characterization, cofire limits, and evaluation of quality improvement measures.

In many low-income cities, a high proportion of fecal sludge, the excreta and blackwater collected from onsite sanitation systems such as pit latrines, is not safely managed. This constitutes a major danger to environmental and human health. The water, sanitation, and hygiene sector has recognized that valorization of treated fecal sludge could offset the upfront cost of treatment by using it as a fuel source. The few quantitative studies on fecal sludge fuel published to date have focused on heating value, moisture, ash fraction, and heavy metals. However, other factors impacting fuel utility, specifically ash speciation, have not been adequately quantified for fecal sludge. This study contributes to closing that gap and shows the value of more detailed quantification. It first characterizes fecal sludge samples from Colorado and Uganda, confirms that the fuel is better if cofired with other biomass, and outlines a framework for determining safe cofire ratios. Second, the study evaluates two methods for improving fecal sludge as a fuel: carbonization and ash leaching. Carbonization of fecal sludge did not improve fuel quality, but leaching showed promise in ash reduction.

Organic Chemical Characterization and Mass Balance of a Hydraulically Fractured Well: From Fracturing Fluid to Produced Water over 405 Days.

A long-term field study (405 days) of a hydraulically fractured well from the Niobrara Formation in the Denver-Julesburg Basin was completed. Characterization of organic chemicals used in hydraulic fracturing and their changes through time, from the preinjected fracturing fluid to the produced water, was conducted. The characterization consisted of a mass balance by dissolved organic carbon (DOC), volatile organic analysis by gas chromatography/mass spectrometry, and nonvolatile organic analysis by liquid chromatography/mass spectrometry. DOC decreased from 1500 mg/L in initial flowback to 200 mg/L in the final produced water. Only ∼11% of the injected DOC returned by the end of the study, with this 11% representing a maximum fraction returned since the formation itself contributes DOC. Furthermore, the majority of returning DOC was of the hydrophilic fraction (60-85%). Volatile organic compound analysis revealed substantial concentrations of individual BTEX compounds (0.1-11 mg/L) over the 405-day study. Nonvolatile organic compounds identified were polyethylene glycols (PEGs), polypropylene glycols (PPG), linear alkyl-ethoxylates, and triisopropanolamine (TIPA). The distribution of PEGs, PPGs, and TIPA and their ubiquitous presence in our samples and the literature illustrate their potential as organic tracers for treatment operations or in the event of an environmental spill.

Simultaneous atrazine degradation and E. coli inactivation by simulated solar photo-Fenton-like process using persulfate.

This work evaluated the feasibility of a photo-Fenton-like process using persulfate (PS) and ferrous iron (Fe2+) under simulated solar radiation for degrading the herbicide atrazine (ATZ, 6-Chloro-N-ethyl-N'-isopropyl-1,3,5-triazine-2,4-diamine) and inactivating E. coli. Milli Q water, lake water, and diluted wastewater effluents were spiked both simultaneously and separately with ATZ (4 mg/L) and E. coli (105 CFU/mL), and exposed to treatment. A method for determining the average irradiance throughout the water media in the UV(A+B) range of the Xe lamp emission was developed for bench-scale experiments. These values were used to calculate the UV(A+B) fluences and the solar UV(A+B) energy doses per unit of volume (QUV(A+B), kJ/L). The obtained kinetic data were presented versus energy dose. Treatment of lake water at near-neutral pH was ineffective via the photo-Fenton-like process, attaining only 20% ATZ removal and 1-log reduction of E. coli. In Milli Q water and wastewater, the complete degradation of ATZ in the absence of bacteria was observed at an average energy dose of 1.5 kJ/L (60 min), while in the presence of cells the degradation efficiency was ∼60%. When ATZ was present, E. coli inactivation was also affected in Milli Q water, with 1.4-log reduction (93%) at a dose of 1.6 kJ/L (60 min), whereas in wastewater complete inactivation was achieved at a lower dose of 1.3 kJ/L (45 min). The energy requirements on a QUV(A+B) basis for simultaneous 90% ATZ removal and 99.99% E. coli inactivation in Milli Q water and wastewater were shown to be less than 10 kJ/L. This suggests the solar/PS/Fe2+ system is promising for simultaneous treatment and disinfection of wastewater effluents.

Integrative Advanced Oxidation and Biofiltration for Treating Pharmaceuticals in Wastewater.

Advanced oxidation of active pharmaceutical ingredients (APIs) in wastewater produces transformation products (TPs) that are often more biodegradable than the parent compounds. Secondary effluent from a wastewater treatment plant was treated using UV-based advanced oxidation (LPUV/H2O2 and MPUV/NO3) followed by biological aerated filtration (BAF), and different APIs and their transformation products were monitored. The advanced oxidation processes degraded the APIs by 55-87% (LPUV/H2O2) and 58-95% (MPUV/NO3), while minor loss of APIs was achieved in the downstream BAF system. Eleven TPs were detected following oxidation of carbamazepine (5) and iopromide (6); three key TPs were biodegraded in the BAF system. The other TPs remained relatively constant in the BAF. The decrease in UV absorbance (UVA254) of the effluent in the BAF system was linearly correlated to the degradation of the APIs (for the MPUV/NO3-BAF), and can be applied to monitor the biotransformation of APIs in biological-based systems.

Comparison of UV-Induced Inactivation and RNA Damage in MS2 Phage across the Germicidal UV Spectrum.

Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength. The bacteriophage was exposed to monochromatic UV irradiation from a tunable laser at wavelengths of between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (reverse transcription-quantitative PCR) was performed to measure genomic damage for comparison with genomic damage at 253.7 nm. The results indicate that the rates of RNA damage closely mirror the loss of viral infectivity across the germicidal UV spectrum. This demonstrates that genomic damage is the dominant cause of MS2 inactivation from exposure to germicidal UV irradiation. These findings contrast those for adenovirus, for which MS2 is used as a viral surrogate for validating polychromatic UV reactors.

Application of metabolite profiling tools and time-of-flight mass spectrometry in the identification of transformation products of iopromide and iopamidol during advanced oxidation.

The efficiency of wastewater treatment systems in removing pharmaceuticals is often assessed on the basis of the decrease in the concentration of the parent compound. However, what is perceived as "removal" during treatment may not necessarily mean mineralization of the pharmaceutical compound but simply conversion into different transformation products (TPs). Using liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (LC-QToF-MS), we demonstrated conversion of iopromide in wastewater to at least 14 TPs after an advanced oxidation process (AOP) using UV (fluence = 1500 mJ/cm(2)) and H2O2 (10 mg/L). Due to the complexity of the wastewater matrix, the initial experiments were performed using a high concentration (10 mg/L) of iopromide in order to facilitate the identification of TPs. Despite the high concentration of iopromide used, cursory inspection of UV and mass spectra only revealed four TPs in the chromatograms of the post-AOP samples. However, the use of METLIN database and statistics-based profiling tools commonly used in metabolomics proved effective in discriminating between background signals and TPs derived from iopromide. High-resolution mass data allowed one to predict molecular formulas of putative TPs with errors below 5 ppm relative to the observed m/z. Tandem mass spectrometry (MS/MS) data and isotope pattern comparisons provided necessary information that allowed one to elucidate the structure of iopromide TPs. The presence of the proposed iopromide TPs was determined in unspiked wastewater from a municipal wastewater treatment plant, but no iopromide and TPs were detected. Using analogous structural modifications and oxidation that results from the AOP treatment of iopromide, the potential TPs of iopamidol (a structurally similar compound to iopromide) were predicted. The same mass fragmentation pattern observed in iopromide TPs was applied to the predicted iopamidol TPs. LC-QToF-MS revealed the presence of two iopamidol TPs in unspiked AOP-treated wastewater.

Reactivation of Giardia lamblia cysts after exposure to low-pressure UV irradiation.

In this study, we determined the repair capabilities of Giardia lamblia cysts when they were exposed to low-pressure (LP) UV and then 4 different repair conditions. A UV collimated beam apparatus was used to expose shallow suspensions of G. lamblia cysts in buffered reagent water (PBS, pH 7.2) to various doses of LP UV irradiation. After UV irradiation, samples were exposed to 4 repair conditions (light and dark repair conditions with 2 temperatures (25 °C and 37 °C) for each condition). The inactivation of G. lamblia cysts by LP UV was very extensive (∼ 5 log10) even with a low dose of LP UV (1 mJ/cm(2)). More importantly, there was significant restoration of infectivity in G. lamblia cysts when they were exposed to a low dose of LP UV and then to all the repair conditions tested. Overall, the results of this study indicate that G. lamblia cysts do have the ability to repair their UV-damaged DNA when they are exposed to low doses of LP UV irradiation. This is the first study to report the presence of repair in UV-irradiated G. lamblia cysts.