Enhanced Inactivation of <i>Bacillus subtilis</i> Spores during Solar Photolysis of Free Available Chlorine

Forsyth, Jenna E.; Zhou, Peiran; Mao, Quanxin; Asato, Shelby S.; Meschke, John Scott; Dodd, Michael C.

doi:10.1021/es401906x

Cited by 82 publications

(60 citation statements)

References 62 publications

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“…Therefore, NaClO solution with UV irradiation pretreatment appears to be an effective way to enhance NO removal efficiency and reduce the NaClO consumption. According to the comparison results of four different reaction conditions, the UV-enhanced mechanism may be explained by the following reactions [24,[27][28][29]:…”

Section: Comparison Of Different Reaction Conditionsmentioning

confidence: 99%

UV-Enhanced NaClO Oxidation of Nitric Oxide from Simulated Flue Gas

Yang

Han

Dong

et al. 2016

Journal of Chemistry

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A wet de-NOxtechnique based on an UV-enhanced NaClO oxidation process was investigated for simulated flue gas of a diesel engine using a bench-scale reaction chamber. The effects of UV irradiation time, initial pH value, and available chlorine concentration of NaClO solution were studied, respectively. The results showed that when the UV irradiation time was 17.5 min and the initial pH value of NaClO solution was 6, NO removal efficiency of UV/NaClO solution was increased by 19.6% compared with that of NaClO solution. Meanwhile, when the available chlorine concentration of NaClO solution decreased from 0.1 wt% to 0.05 wt%, the enhancement in NO removal efficiency of UV/NaClO solution increased from 19.6% to 24%, compared with that of NaClO solution. The reaction pathways of NaClO solution photolysis and NO removal by UV/NaClO process were preliminarily discussed. The results suggested that HOCl might be the most active species that released many UV-induced photooxidants through photolysis reactions, which played an important role in NO removal process.

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Section: Comparison Of Different Reaction Conditionsmentioning

confidence: 99%

UV-Enhanced NaClO Oxidation of Nitric Oxide from Simulated Flue Gas

Yang

Han

Dong

et al. 2016

Journal of Chemistry

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“…Applications of photo-Fenton processes to enhance microbial inactivation kinetics have been successfully demonstrated in a variety of natural water matrixes under eld conditions at scales ranging from 1 L water bottles up to 50 L. 254 An alternative approach to SODIS enhancement is the solar "photoactivation" of free available chlorine (HOCl/OCl À ) to yield cOH, RHS, and O 3 . 261 The production of cOH and O 3 during exposure of chlorine-containing solutions to natural sunlight under conditions typical of SODIS processes (e.g., pH 8, T ¼ 33 C) can accelerate inactivation of highly chlorine-resistant B.…”

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confidence: 99%

“…24,25 This approach could present interesting opportunities for improving the effectiveness of either chlorine-based disinfection or SODIS. 261,262 It is important to note that photoactivation of free available chlorine by UVB and UVA wavelengths may lead to elevated levels of disinfection byproducts. 263 Thus, the use of this approach would require careful selection of treatment conditions to minimize risks of byproduct exposure while maximizing inactivation of recalcitrant pathogens.…”

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confidence: 99%

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

Nelson

Boehm

Davies‐Colley

et al. 2018

Environ. Sci.: Processes Impacts

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201

221

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Health-relevant microorganisms present in natural surface waters and engineered treatment systems that are exposed to sunlight can be inactivated by a complex set of interacting mechanisms. The net impact of sunlight depends on the solar spectral irradiance, the susceptibility of the specific microorganism to each mechanism, and the water quality; inactivation rates can vary by orders of magnitude depending on the organism and environmental conditions. Natural organic matter (NOM) has a large influence, as it can attenuate radiation and thus decrease inactivation by endogenous mechanisms. Simultaneously NOM sensitizes the formation of reactive intermediates that can damage microorganisms via exogenous mechanisms. To accurately predict inactivation and design engineered systems that enhance solar inactivation, it is necessary to model these processes, although some details are not yet sufficiently well understood. In this critical review, we summarize the photo-physics, -chemistry, and -biology that underpin sunlight-mediated inactivation, as well as the targets of damage and cellular responses to sunlight exposure. Viruses that are not susceptible to exogenous inactivation are only inactivated if UVB wavelengths (280-320 nm) are present, such as in very clear, open waters or in containers that are transparent to UVB. Bacteria are susceptible to slightly longer wavelengths. Some viruses and bacteria (especially Gram-positive) are susceptible to exogenous inactivation, which can be initiated by visible as well as UV wavelengths. We review approaches to model sunlightmediated inactivation and illustrate how the environmental conditions can dramatically shift the inactivation rate of organisms. The implications of this mechanistic understanding of solar inactivation are discussed for a range of applications, including recreational water quality, natural treatment systems, solar disinfection of drinking water (SODIS), and enhanced inactivation via the use of sensitizers and photocatalysts. Finally, priorities for future research are identified that will further our understanding of the key role that sunlight disinfection plays in natural systems and the potential to enhance this process in engineered systems. Environmental signicanceThe manuscript provides a comprehensive synthesis of the current understanding of the mechanisms by which sunlight causes damage to microorganisms, ultimately leading to inactivation. This topic is important for understanding the fate and transport of microbiological contaminants in all sunlit surface waters, including fresh and marine ecosystems, as well as engineered treatment systems.

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“…For the assessment of bacterial viability and disinfection efficiency, cultivation-based plating methods have been extensively applied for quantifying the viability of laboratory-culturable indicator bacteria during various disinfection experiments (Forsyth et al, 2013;Gamage et al, 2013;Gerrity et al, 2012;Van Nevel et al, 2017). However, conventional plating methods cannot well detect the majority of autochthonous bacteria in water and wastewater, as many bacteria are not cultivable under specific conditions Van Nevel et al, 2017).…”

Section: ; Vonmentioning

confidence: 99%

“…After one hour, 20 mL of samples were filtered by 0.45 μm filter for chemical and spectroscopic analyses and the residual samples were taken for plating (E. coli experiments only) and FCM analyses immediately. Colony forming units (CFU) were measured by means of a spot-titer plating assay (Beck et al, 2009;Forsyth et al, 2013), which is characterized by dispensing 10-μL droplets of samples on the LB-agar plate (Text S2 and Fig. S2).…”

Section: Ozonation Experiments With Spiked E Coli or Autochthonous Bmentioning

confidence: 99%

Applying UV absorbance and fluorescence indices to estimate inactivation of bacteria and formation of bromate during ozonation of water and wastewater effluent

Cheng

Cai

et al. 2018

Water Research

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Ozone is an effective oxidant and disinfectant commonly used for elimination of micropollutants and inactivation of resistant microbes. However, undesirable oxidation/disinfection byproducts such as bromate might form during ozonation. In this study, the UV absorbance and fluorescence indices were applied as surrogate indicators for predicting the inactivation of bacteria and formation of bromate during ozonation of water and wastewater effluents. The inactivation efficiencies of lab-cultured Escherichia coli (E. coli) and autochthonous bacteria were measured by plating (for E. coli only) and flow cytometry with fluorescence staining. During ozonation of E. coli spiked into wastewater effluents (∼10 cell/mL), the priority of inactivation efficiency determined by different cell viability methods were in the order of CFU > membrane damage > DNA damage. Approximately, 99% membrane damage and/or 90% DNA damage are conservatively supposed as an indicator for sufficient bacterial inactivation as well as degradation of antibiotic resistance genes. The related required O dosing thresholds for sufficient inactivation of E. coli and autochthonous bacteria refer to ∼0.6 O/DOC (g/g), ∼50% decrease of UVA254, ∼60% decrease of UVA280, or ∼80% decrease of humic-like fluorescence. Within the range of 10-10 cell/mL, the bacterial concentration did not have significant effects on the required thresholds of the specific O doses or spectroscopic indicators required for bacterial inactivation. The addition of 50 mM tert-BuOH as ·OH scavenger increased the required specific ozone doses but decreased the losses of spectroscopic indicators necessary for sufficient bacterial inactivation, and also suggested that the membrane/DNA damages for bacterial inactivation were mainly attributed to the direct O attacks. The bromate concentration was determined using ion chromatography with MS/MS detection. The results showed that when O was dosed at the required thresholds for sufficient bacterial inactivation, bromate formation could usually be suppressed below 10 μg/L. The present work supports that it is possible to reach a balance between bacterial inactivation and bromate formation.

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Enhanced Inactivation of Bacillus subtilis Spores during Solar Photolysis of Free Available Chlorine

Cited by 82 publications

References 62 publications

UV-Enhanced NaClO Oxidation of Nitric Oxide from Simulated Flue Gas

UV-Enhanced NaClO Oxidation of Nitric Oxide from Simulated Flue Gas

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

Applying UV absorbance and fluorescence indices to estimate inactivation of bacteria and formation of bromate during ozonation of water and wastewater effluent

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