Impact of storm events on disinfection byproduct precursors in a drinking water source in the Northeastern United States.

Storm events play a crucial role in organic matter transport within watersheds and can increase the concentration and alter the composition of NOMs and DBP formation potential. To assess the impact that storm events can have on drinking water quality, samples were collected and analyzed across four storm events in the Neversink River, Catskill region, New York in 2019 and 2022. Source water natural organic matter (NOM) was characterized, and the change of NOM quality was evaluated due to storm impacts. During storm events, a high level of NOM mobilization is initiated by heavy precipitation causing overland flow and a rise in the water table. In this way, storms result in increased access to stored NOM pools that are generated during inter-storm periods. A significant correlation was observed between several organic water quality parameters such as UV absorbance (UV254), dissolved organic carbon (DOC) and chlorine demand. Precursors for the total trihalomethanes (TTHM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) exhibited comparable patterns with UV254, DOC, and chlorine demand for four storms. Despite the potential for increased dilution resulting from higher discharges, all organic water quality parameters, including yields of disinfection byproducts (i.e., DBP precursors), exhibited elevated concentrations during periods of higher flows. Three of the four storms showed hysteresis patterns with higher observed concentrations of organic constituents in the falling limb of the hydrographs. Precursors for the nitrogenous DBPs (N-DBPs) were proportional to the DOC for all four storms. The coefficient of determination (R2) for TTHM, DCAA, TCAA with UV254 is higher (R2 0.92-0.98) than corresponding correlations with DOC (R2 0.89-0.92). The R2 for UV254 showed the following hierarchy: DCAA≈TCAA>TTHM. Additionally, the R2 for DOC and specific ultraviolet absorbance (SUVA) had the following hierarchy: DCAA>TCAA>TTHM and TCAA>DCAA>TTHM respectively. A significant correlation between UV254 and DOC (R = 0.99) for all storms was observed. Chlorine demand also yielded a strong correlation (R = 0.91∼0.98) with UV254 and DOC. This research indicates that a significant and disproportionate export of NOM to source waters occurs during storm events compared to baseflow conditions. Consequently, it is recommended for drinking water treatment facilities to reassess chlorine dosages during these events. Treatment plants can employ UV254 as a tool to determine appropriate chlorine dosages, aiming to mitigate DBP formation in treated waters.

UV emitting glass: A promising strategy for biofilm inhibition on transparent surfaces.

Marine biofouling causes serious environmental problems and has adverse impacts on the maritime industry. Biofouling on windows and optical equipment reduces surface transparency, limiting their application for on-site monitoring or continuous measurement. This work illustrates that UV emitting glasses (UEGs) can prevent the establishment and growth of biofilm on the illuminated surfaces. Specifically, this paper describes how UEGs are enabled by innovatively modifying the surfaces of the glass with light scattering particles. Modification of glass surface with silica nanoparticles at a concentration 26.5 µg/cm2 resulted in over ten-fold increase in UV irradiance, while maintaining satisfactory visible and IR transparency metrics of over 99 %. The UEG reduced visible biological growth by 98 % and resulted in a decrease of 1.79 log in detected colony forming units when compared to the control during a 20 day submersion at Port Canaveral, Florida, United States. These findings serve as strong evidence that UV emitting glass should be explored as a promising approach for biofilm inhibition on transparent surfaces.

Germicidal glowsticks: Side-emitting optical fibers inhibit Pseudomonas aeruginosa and Escherichia coli on surfaces.

This paper investigates using UV-C side-emitting optical fibers (SEOFs) to prevent growth of pathogenic bacteria (Pseudomonas aeruginosa and Escherichia coli) on nutrient-rich surfaces. Attaching a SEOF to a single 265 nm light emitting diode (LED) increases irradiation area by >1000x and provides continuous low-irradiance of UV-C light to a large surface area. A zone-of-inhibition protocol was developed to quantify bacterial growth prevention on an agar plate around one SEOF. The inhibition zone increased linearly with irradiance time until achieving a maximum inhibition zone of 2.5 to 3 cm, which received ~ 4.3 mJ/cm2 of 265 nm light in 2 hours. The surviving lawn edge bacterial colonies did not develop UV resistance after two generations of exposure. The agar plate remained bio-available after UV exposure, and bacteria could be grown on pre-illuminated area in the absence of UV-C light. Whereas we previously demonstrated SEOFs can inactivate planktonic bacteria, herein we show the ability of SEOFs to prevent bacteria growth on surfaces. This is the first step towards developing technologies with multiple SEOFs to inhibit biofilm growth on surfaces, which is a ubiquitous challenge across multiple applications from membrane surfaces to surfaces in pipes or water storage systems.

Germicidal Ultraviolet Light Does Not Damage or Impede Performance of N95 Masks Upon Multiple Uses.

The COVID-19 pandemic is increasing the need for personal protective equipment (PPE) worldwide, including the demand for facial masks used by healthcare workers. Disinfecting and reusing these masks may offer benefits in the short term to meet urgent demand. Germicidal ultraviolet light provides a nonchemical, easily deployable technology capable of achieving inactivation of H1N1 virus on masks. Working with N95-rated masks and nonrated surgical masks, we demonstrated that neither 254 nor 265 nm UV-C irradiation at 1 and 10 J/cm2 had adverse effects on the masks' ability to remove aerosolized virus-sized particles. Additional testing showed no change in polymer structure, morphology, or surface hydrophobicity for multiple layers in the masks and no change in pressure drop or tensile strength of the mask materials. Results were similar when applying 254 nm low-pressure UV lamps and 265 nm light-emitting diodes. On the basis of the input from healthcare workers and our findings, a treatment system and operational manual were prepared to enable treatment and reuse of N95 facial masks. Knowledge gained during this study can inform techno-economic analyses for treating and reusing masks or lifecycle assessments of options to reduce the enormous waste production of single-use PPE used in the healthcare system, especially during pandemics.

Nanoparticle and Transparent Polymer Coatings Enable UV-C Side-Emission Optical Fibers for Inactivation of Escherichia coli in Water.

Pathogenic bacteria pose a health threat and operational challenge in drinking water. UV-C light-emitting diodes (UV-C LEDs) are becoming a competitive disinfection technology but are limited by their small irradiation area. Side-emitting optical fibers (SEOFs) can serve as a UV-C LED light delivery technology for reactors or tubing. Modifying the surfaces of conventional optical fibers with scattering centers allows for side emission of 265 nm radiation from an LED for microbial inactivation in water. Solid-material absorbance and flux measurements differentiated light absorption from scattering for all materials. Silica spheres >200 nm in diameter achieved higher scattering than smaller silica. A critical discovery was that treating the silica-coated optical fiber in a solution of high ionic strength increased UV-C side emission by greater than 6-fold. Additionally, the cladding polymer Cytop had negligible absorbance at 265 nm wavelength. A scalable four-step treatment process was developed to fabricate the novel SEOF. Attached to a 265 nm LED, the side-emitting optical fiber achieved 2.9 log inactivation of Escherichia coli at a delivery dose of 15 mJ/cm2. The results illustrate proof of concept that UV-C SEOFs can inactivate E. coli and should be further explored for delivering LED light into water.

Optical fiber-mediated photosynthesis for enhanced subsurface oxygen delivery.

Remediation of polluted groundwater often requires oxygen delivery into subsurface to sustain aerobic bacteria. Air sparging or injection of oxygen containing solutions (e.g., hydrogen peroxide) into the subsurface are common. In this study visible light was delivered into the subsurface using radially emitting optical fibers. Phototrophic organisms grew near the optical fiber in a saturated sand column. When applying light in on-off cycles, dissolved oxygen (DO) varied from super saturation levels of >15 mg DO/L in presence of light to under-saturation (<5 mg DO/L) in absence of light. Non-photosynthetic bacteria dominated at longer radial distances from the fiber, presumably supported by soluble microbial products produced by the photosynthetic microorganisms. The dissolved oxygen variations alter redox condition changes in response to light demonstrate the potential to biologically deliver oxygen into the subsurface and support a diverse microbial community. The ability to deliver oxygen and modulate redox conditions on diurnal cycles using solar light may provide a sustainable, long term strategy for increasing dissolved oxygen levels in subsurface environments and maintaining diverse biological communities.

Electrical energy per order and current efficiency for electrochemical oxidation of p-chlorobenzoic acid with boron-doped diamond anode.

Electrochemical oxidation (EO) is an advanced oxidation process for water treatment to mineralize organic contaminants. While proven to degrade a range of emerging pollutants in water, less attention has been given to quantify the effect of operational variables such applied current density and pollutant concentration on efficiency and energy requirements. Particular figures of merit were mineralization current efficiency (MCE) and electrical energy per order (EEO). Linear increases of applied current exponentially decreased the MCE due to the enhancement of undesired parasitic reactions that consumed generated hydroxyl radical. EEO values ranged from 39.3 to 331.8 kW h m-3 order-1. Increasing the applied current also enhanced the EEO due to the transition from kinetics limited by current to kinetics limited by mass transfer. Further increases in current did not influence the removal rate, but it raised the EEO requirement. The EEO requirement diminished when decreasing initial pollutant loading with the increase of the apparent kinetic rate because of the relative availability of oxidant per pollutant molecule in solution at a defined current. Oxidation by-products released were identified, and a plausible degradative pathway has been suggested.