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Chiyenge M, Silverman AI. Effect of pH on endogenous sunlight inactivation rates of laboratory strain and wastewater sourced E. coli and enterococci. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2022; 24:2167-2177. [PMID: 36226678 DOI: 10.1039/d2em00227b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Understanding the influence of environmental factors like pH on solar disinfection in sunlight-dependent wastewater treatment systems can aid in improving their design. Previous research found pH to influence the solar disinfection rates of bacteria in water containing exogenous photosensitizers that facilitate photo-oxidative inactivation. However, limited research has been conducted on the role of external pH on endogenous solar inactivation processes that occur independent of exogenous photosensitizers. As such, we studied the inactivation rates of laboratory-cultured and wastewater-sourced E. coli and enterococci in sensitizer-free matrices with pH ranging from 4 to 10 under full-spectrum and UVB-filtered simulated sunlight. Elevated solar inactivation rates were observed at pH 4 for all bacterial populations evaluated, and at pH 10 for laboratory-cultured and wastewater-sourced E. coli. Dark inactivation was observed at the pH extremes for some bacteria, but did not contribute significantly to the increased inactivation rates observed under simulated sunlight at these pH, except for laboratory-cultured E. coli at pH 10. UVB light was found to play an important role in sunlight inactivation, albeit the contribution of UVB light to solar inactivation observed for Enterococcus spp. diminished at pH 4 and 5, suggesting that indirect endogenous inactivation pathways facilitated by longer wavelength light were enhanced under acidic conditions. Our findings demonstrate that external pH affects the kinetics of endogenous sunlight inactivation processes, and the results have potential to be integrated into models for predicting inactivation kinetics in sunlight-mediated treatment systems that operate over a range of pH conditions.
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Affiliation(s)
- Mwale Chiyenge
- Department of Civil and Urban Engineering, Tandon School of Engineering, New York University, 6 Metrotech Center, Brooklyn, NY 11201, USA.
| | - Andrea I Silverman
- Department of Civil and Urban Engineering, Tandon School of Engineering, New York University, 6 Metrotech Center, Brooklyn, NY 11201, USA.
- School of Global Public Health, New York University, New York, NY 10003, USA
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2
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Chambonniere P, Bronlund JE, Guieysse B. Study from microcosms and mesocosms reveals Escherichia coli removal in high rate algae ponds during domestic wastewater treatment is primarily caused by dark decay. PLoS One 2022; 17:e0265576. [PMID: 35298558 PMCID: PMC8929646 DOI: 10.1371/journal.pone.0265576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 03/03/2022] [Indexed: 11/24/2022] Open
Abstract
While high rate algal ponds (HRAPs) can provide efficient pathogen removal from wastewater, the mechanisms involved remain unclear. To address this knowledge gap, the mechanisms potentially causing Escherichia coli (E. coli) removal during microalgae-based wastewater treatment were successively assessed using laboratory microcosms designed to isolate known mechanisms, and bench scale assays performed in real HRAP broth. During laboratory assays, E. coli decay was only significantly increased by alkaline pH (above temperature-dependent thresholds) due to pH induced toxicity, and direct sunlight exposure via UV-B damage and/or endogenous photo-oxidation. Bench assays confirmed alkaline pH toxicity caused significant decay but sunlight-mediated decay was not significant, likely due to light attenuation in the HRAP broth. Bench assays also evidenced the existence of uncharacterized ‘dark’ decay mechanism(s) not observed in laboratory microcosms. To numerically evaluate the contribution of each mechanism and the uncertainty associated, E. coli decay was modelled assuming dark decay, alkaline pH induced toxicity, and direct sunlight-mediated decay were independent mechanisms. The simulations confirmed E. coli decay was mainly caused by dark decay during bench assays (48.2–89.5% estimated contribution to overall decay at the 95% confidence level), followed by alkaline-pH induced toxicity (8.3–46.5%), and sunlight-mediated decay (0.0–21.9%).
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Affiliation(s)
- Paul Chambonniere
- Department of Chemical and Bioprocess Engineering, School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
- * E-mail:
| | - John E. Bronlund
- Department of Chemical and Bioprocess Engineering, School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
| | - Benoit Guieysse
- Department of Chemical and Bioprocess Engineering, School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand
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3
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Dunn FB, Silverman AI. Sunlight Photolysis of Extracellular and Intracellular Antibiotic Resistance Genes tetA and sul2 in Photosensitizer-Free Water. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:11019-11028. [PMID: 34346694 DOI: 10.1021/acs.est.1c00732] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Antibiotic resistance genes (ARGs; the genetic material in bacteria that encode for resistance to antibiotics) have been found in the aquatic environment, raising concerns of an environmental transmission route. In an effort to contribute to models predicting the fate of ARGs in the environment-to design control measures, predict health risks, inform ARG surveillance activities, and prioritize policy interventions-and given the importance of sunlight in damaging DNA, we evaluated the sunlight photolysis kinetics of antibiotic-resistant bacteria (ARB) and ARGs under laboratory conditions, focusing on Escherichia coli SMS-3-5 and its ARGs tetA and sul2. Experiments were conducted in the absence of photosensitizers, and ARG decay rates were quantified by quantitative polymerase chain reaction (qPCR) with short and long amplicon targets. Long amplicon qPCR targets quantified greater photolysis rate constants, due to greater ARG coverage. After a lag phase, intracellular ARG had faster decay rates than extracellular ARG, likely due to the contribution of intracellular indirect photolysis processes. Furthermore, all ARG decay rates were significantly slower than those of E. coli. Decay rate constants and quantum yields are presented as foundational work in the development of models to describe the persistence of ARGs in sunlit, environmental waters.
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Affiliation(s)
- Fiona B Dunn
- Department of Civil and Urban Engineering, Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
| | - Andrea I Silverman
- Department of Civil and Urban Engineering, Tandon School of Engineering, New York University, Brooklyn, New York 11201, United States
- School of Global Public Health, New York University, New York, New York 10003, United States
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Loeb SK, Jennings WC, Wigginton KR, Boehm AB. Sunlight Inactivation of Human Norovirus and Bacteriophage MS2 Using a Genome-Wide PCR-Based Approach and Enzyme Pretreatment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:8783-8792. [PMID: 34101449 DOI: 10.1021/acs.est.1c01575] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Human norovirus (hNoV) is an important etiology of gastrointestinal illness and can be transmitted via ingestion of contaminated water. Currently impractical to culture, hNoV detection is reliant on real-time polymerase chain reaction (RT-PCR)-based methods. This approach cannot distinguish between infective and inactivated viruses because intact regions of the RNA genome can amplify even if the damage is present in other regions of the genome or because intact genetic material is not contained within an infectious virion. Herein, we employ a multiple long-amplicon RT-qPCR extrapolation approach to assay genome-wide damage and an enzymatic pretreatment to study the impact of simulated sunlight on the infectivity of hNoV in clear, sensitizer-free water. Using MS2 coliphage as an internal control, the genome-wide damage extrapolation approach, previously successfully applied for UV-254 inactivation, vastly overestimated sunlight inactivation, suggesting key differences in photoinactivation under different spectral conditions. hNoV genomic RNA was more susceptible to simulated sunlight degradation per base compared to MS2 genomic RNA, while enzymatic pretreatment indicated that hNoV experienced more capsid damage than MS2. This work provides practical and mechanistic insight into the endogenous sunlight inactivation of single-stranded RNA bacteriophage MS2, a widely used surrogate, and hNoV GII.4 Sydney, an important health-relevant virus, in clear sensitizer-free water.
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Affiliation(s)
- Stephanie K Loeb
- Department of Civil & Environmental Engineering, Stanford University, Stanford, California 94305, United States
- Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt), Stanford, California 94305, United States
| | - Wiley C Jennings
- Department of Civil & Environmental Engineering, Stanford University, Stanford, California 94305, United States
| | - Krista Rule Wigginton
- Department of Civil & Environmental Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alexandria B Boehm
- Department of Civil & Environmental Engineering, Stanford University, Stanford, California 94305, United States
- Engineering Research Center (ERC) for Re-inventing the Nation's Urban Water Infrastructure (ReNUWIt), Stanford, California 94305, United States
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5
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Dahl NW, Woodfield PL, Simpson BAF, Stratton HM, Lemckert CJ. Effect of turbulence, dispersion, and stratification on Escherichia coli disinfection in a subtropical maturation pond. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 288:112470. [PMID: 33823449 DOI: 10.1016/j.jenvman.2021.112470] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 03/12/2021] [Accepted: 03/22/2021] [Indexed: 06/12/2023]
Abstract
Sunlight disinfection is important for treatment of wastewater within maturation ponds. This study analyses the movement of Escherichi coli within a slice of a maturation pond, being affected by stratification, sunlight attenuation and mixing driven by wind shear and natural convection using computational fluid dynamics (CFD). Since the exposure to ultraviolet light is most effective in the near-surface region of the pond, natural convective mixing mechanisms to transport the pathogens from the lower parts of the pond are critical for disinfection efficacy. Different turbulence models are considered for closure of the momentum conservation equations and compared with a laminar flow simulation and a completely stirred tank reactor (CSTR) model. The effect of turbulence and stratification is shown to be significant for thermal and velocity distributions, and predictions of E. coli die-off. Greater volume-averaged E. coli die-off was predicted by the computationally convenient CSTR model than the CFD turbulence and laminar models. The simulation results are compared with experimental data and show that complete vertical mixing occurs in a diurnal pattern aiding die-off in sunlight-attenuating water. Practical applications of the model can assist in management strategies for maturation ponds such as off-take locations/times and evaluating seasonal variations in sunlight disinfection.
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Affiliation(s)
- Nick W Dahl
- School of Engineering & Built Environment, Griffith University, Gold Coast, 4222, Australia.
| | - Peter L Woodfield
- School of Engineering & Built Environment, Griffith University, Gold Coast, 4222, Australia.
| | - Ben A F Simpson
- School of Science & Technology, Nottingham Trent University, UK.
| | - Helen M Stratton
- School of Engineering & Built Environment, Griffith University, Gold Coast, 4222, Australia.
| | - Charles J Lemckert
- School of Design and the Built Environment, University of Canberra, 2617, Australia.
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García-Gil Á, García-Muñoz RA, McGuigan KG, Marugán J. Solar Water Disinfection to Produce Safe Drinking Water: A Review of Parameters, Enhancements, and Modelling Approaches to Make SODIS Faster and Safer. Molecules 2021; 26:molecules26113431. [PMID: 34198857 PMCID: PMC8201346 DOI: 10.3390/molecules26113431] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 01/16/2023] Open
Abstract
Solar water disinfection (SODIS) is one the cheapest and most suitable treatments to produce safe drinking water at the household level in resource-poor settings. This review introduces the main parameters that influence the SODIS process and how new enhancements and modelling approaches can overcome some of the current drawbacks that limit its widespread adoption. Increasing the container volume can decrease the recontamination risk caused by handling several 2 L bottles. Using container materials other than polyethylene terephthalate (PET) significantly increases the efficiency of inactivation of viruses and protozoa. In addition, an overestimation of the solar exposure time is usually recommended since the process success is often influenced by many factors beyond the control of the SODIS-user. The development of accurate kinetic models is crucial for ensuring the production of safe drinking water. This work attempts to review the relevant knowledge about the impact of the SODIS variables and the techniques used to develop kinetic models described in the literature. In addition to the type and concentration of pathogens in the untreated water, an ideal kinetic model should consider all critical factors affecting the efficiency of the process, such as intensity, spectral distribution of the solar radiation, container-wall transmission spectra, ageing of the SODIS reactor material, and chemical composition of the water, since the substances in the water can play a critical role as radiation attenuators and/or sensitisers triggering the inactivation process.
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Affiliation(s)
- Ángela García-Gil
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, Móstoles, 28933 Madrid, Spain; (Á.G.-G.); (R.A.G.-M.)
| | - Rafael A. García-Muñoz
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, Móstoles, 28933 Madrid, Spain; (Á.G.-G.); (R.A.G.-M.)
| | - Kevin G. McGuigan
- Department of Physiology & Medical Physics, RCSI University of Medicine and Health Sciences, DO2 YN77 Dublin, Ireland;
| | - Javier Marugán
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, Móstoles, 28933 Madrid, Spain; (Á.G.-G.); (R.A.G.-M.)
- Correspondence:
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Safaie A, Weiskerger CJ, Nguyen TD, Acrey B, Zepp RG, Molina M, Cyterski M, Whelan G, Pachepsky YA, Phanikumar MS. Modeling the photoinactivation and transport of somatic and F-specific coliphages at a Great Lakes beach. JOURNAL OF ENVIRONMENTAL QUALITY 2020; 49:1612-1623. [PMID: 33150652 PMCID: PMC7859910 DOI: 10.1002/jeq2.20153] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/20/2020] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
Fecal indicator organisms (FIOs), such as Escherichia coli and enterococci, are often used as surrogates of contamination in the context of beach management; however, bacteriophages may be more reliable indicators than FIO due to their similarity to viral pathogens in terms of size and persistence in the environment. In the past, mechanistic modeling of environmental contamination has focused on FIOs, with virus and bacteriophage modeling efforts remaining limited. In this paper, we describe the development and application of a fate and transport model of somatic and F-specific coliphages for the Washington Park beach in Lake Michigan, which is affected by riverine outputs from the nearby Trail Creek. A three-dimensional model of coliphage transport and photoinactivation was tested and compared with a previously reported E. coli fate and transport model. The light-based inactivation of the phages was modeled using organism-specific action spectra. Results indicate that the coliphage models outperformed the E. coli model in terms of reliably predicting observed E. coli/coliphage concentrations at the beach. This is possibly due to the presence of additional E. coli sources that were not accounted for in the modeling. The coliphage models can be used to test hypotheses about potential sources and their behavior and for predictive modeling.
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Affiliation(s)
- Ammar Safaie
- Department of Civil & Environmental Engineering, Michigan State University, East Lansing, MI 48824
| | - Chelsea J. Weiskerger
- Department of Civil & Environmental Engineering, Michigan State University, East Lansing, MI 48824
| | - Tuan D. Nguyen
- Department of Civil & Environmental Engineering, Michigan State University, East Lansing, MI 48824
- Mekong River Commission, Vientiane
| | - Brad Acrey
- Office of Research and Development, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, GA 30605
| | - Richard G. Zepp
- Office of Research and Development, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, GA 30605
| | - Marirosa Molina
- Office of Research and Development, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, GA 30605
| | - Michael Cyterski
- Office of Research and Development, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, GA 30605
| | - Gene Whelan
- Office of Research and Development, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, GA 30605
| | - Yakov A. Pachepsky
- USDA–ARS, Environmental Microbial and Food Safety Lab, Beltsville, MD 20705
| | - Mantha S. Phanikumar
- Department of Civil & Environmental Engineering, Michigan State University, East Lansing, MI 48824
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García-Gil Á, Pablos C, García-Muñoz RA, McGuigan KG, Marugán J. Material selection and prediction of solar irradiance in plastic devices for application of solar water disinfection (SODIS) to inactivate viruses, bacteria and protozoa. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 730:139126. [PMID: 32416507 DOI: 10.1016/j.scitotenv.2020.139126] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 04/10/2020] [Accepted: 04/28/2020] [Indexed: 06/11/2023]
Abstract
Solar water disinfection (SODIS) is a simple, inexpensive and sustainable Household Water Treatment (HWT) that is appropriate for low-income countries or emergency situations. Usually, SODIS involves solar exposure of water contained in transparent polyethylene terephthalate (PET) bottles for a minimum of 6 h. Sunlight, especially UVB radiation, has been demonstrated to photoinactivate bacteria, viruses and protozoa. In this work, an in-depth study of the optical and mechanical properties, weathering and production prices of polymeric materials has been carried out to identify potential candidate materials for manufacturing SODIS devices. Three materials were ruled out (polystyrene (PS), polyvinyl chloride (PVC) and polyethylene (PE)) and four materials were initially selected for study: polymethylmethacrylate (PMMA), polypropylene (PP), polycarbonate (PC) and polyethylene terephthalate (PET). These plastics transmit sufficient solar radiation to kill waterborne pathogens with production costs compensated by their durability under solar exposure. A predictive model has been developed to quantitatively estimate the radiation available for SODIS inside the device as a function of the material and thickness. This tool has two applications: to evaluate design parameters such as thickness, and to estimate experimental requirements such as solar exposure time. In this work, this model evaluated scenarios involving different plastic materials, device thicknesses, and pathogens (Escherichia coli bacterium, MS2 virus and Cryptosporidium parvum protozoon). The developed Solar UV Calculator model is freely available and can be also applied to other customized materials and conditions.
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Affiliation(s)
- Ángela García-Gil
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain
| | - Cristina Pablos
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain
| | - Rafael A García-Muñoz
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain
| | - Kevin G McGuigan
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland (RCSI), Dublin 2, Ireland
| | - Javier Marugán
- Department of Chemical and Environmental Technology (ESCET), Universidad Rey Juan Carlos, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain.
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Zhou NA, Fagnant-Sperati CS, Komen E, Mwangi B, Mukubi J, Nyangao J, Hassan J, Chepkurui A, Maina C, van Zyl WB, Matsapola PN, Wolfaardt M, Ngwana FB, Jeffries-Miles S, Coulliette-Salmond A, Peñaranda S, Shirai JH, Kossik AL, Beck NK, Wilmouth R, Boyle DS, Burns CC, Taylor MB, Borus P, Meschke JS. Feasibility of the Bag-Mediated Filtration System for Environmental Surveillance of Poliovirus in Kenya. FOOD AND ENVIRONMENTAL VIROLOGY 2020; 12:35-47. [PMID: 31679104 PMCID: PMC7052051 DOI: 10.1007/s12560-019-09412-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 10/15/2019] [Indexed: 05/24/2023]
Abstract
The bag-mediated filtration system (BMFS) was developed to facilitate poliovirus (PV) environmental surveillance, a supplement to acute flaccid paralysis surveillance in PV eradication efforts. From April to September 2015, environmental samples were collected from four sites in Nairobi, Kenya, and processed using two collection/concentration methodologies: BMFS (> 3 L filtered) and grab sample (1 L collected; 0.5 L concentrated) with two-phase separation. BMFS and two-phase samples were analyzed for PV by the standard World Health Organization poliovirus isolation algorithm followed by intratypic differentiation. BMFS samples were also analyzed by a cell culture independent real-time reverse transcription polymerase chain reaction (rRT-PCR) and an alternative cell culture method (integrated cell culture-rRT-PCR with PLC/PRF/5, L20B, and BGM cell lines). Sabin polioviruses were detected in a majority of samples using BMFS (37/42) and two-phase separation (32/42). There was statistically more frequent detection of Sabin-like PV type 3 in samples concentrated with BMFS (22/42) than by two-phase separation (14/42, p = 0.035), possibly due to greater effective volume assayed (870 mL vs. 150 mL). Despite this effective volume assayed, there was no statistical difference in Sabin-like PV type 1 and Sabin-like PV type 2 detection between these methods (9/42 vs. 8/42, p = 0.80 and 27/42 vs. 32/42, p = 0.18, respectively). This study demonstrated that BMFS can be used for PV environmental surveillance and established a feasible study design for future research.
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Affiliation(s)
- Nicolette A Zhou
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA
| | - Christine S Fagnant-Sperati
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA
| | - Evans Komen
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - Benlick Mwangi
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - Johnstone Mukubi
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - James Nyangao
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - Joanne Hassan
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - Agnes Chepkurui
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - Caroline Maina
- Kenya Ministry of Health, Afya House, Cathedral Road, P.O. Box 30016, Nairobi, 00100, Kenya
| | - Walda B van Zyl
- Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia, 0007, South Africa
| | - Peter N Matsapola
- Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia, 0007, South Africa
| | - Marianne Wolfaardt
- Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia, 0007, South Africa
| | - Fhatuwani B Ngwana
- Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia, 0007, South Africa
| | - Stacey Jeffries-Miles
- IHRC, Inc. (contracting agency to the Division of Viral Diseases, Centers for Diseases Control and Prevention, Atlanta, GA 30329, USA), 2 Ravinia Drive, Suite 1200, Atlanta, GA, 30329, USA
| | - Angela Coulliette-Salmond
- Division of Viral Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop H17-6, Atlanta, GA, 30329, USA
| | - Silvia Peñaranda
- Division of Viral Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop H17-6, Atlanta, GA, 30329, USA
| | - Jeffry H Shirai
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA
| | - Alexandra L Kossik
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA
| | - Nicola K Beck
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA
| | - Robyn Wilmouth
- PATH, 2201 Westlake Ave, Suite 200, Seattle, WA, 98121, USA
| | - David S Boyle
- PATH, 2201 Westlake Ave, Suite 200, Seattle, WA, 98121, USA
| | - Cara C Burns
- Division of Viral Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop H17-6, Atlanta, GA, 30329, USA
| | - Maureen B Taylor
- Department of Medical Virology, Faculty of Health Sciences, University of Pretoria, Private Bag X323, Arcadia, 0007, South Africa
| | - Peter Borus
- Centre for Viral Research, Kenya Medical Research Institute, Mbagathi Road, P.O. Box 54628, Nairobi, 00200, Kenya
| | - John Scott Meschke
- Department of Environmental and Occupational Health Sciences, University of Washington, 4225 Roosevelt Way NE, Suite 100, Seattle, WA, 98105, USA.
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Wenk J, Nguyen MT, Nelson KL. Natural Photosensitizers in Constructed Unit Process Wetlands: Photochemical Characterization and Inactivation of Pathogen Indicator Organisms. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:7724-7735. [PMID: 31149822 DOI: 10.1021/acs.est.9b01180] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Dissolved organic matter (DOM) is a natural photosensitizer that contributes to the inactivation of microbial pathogens. In constructed treatment wetlands with open water areas DOM can promote sunlight disinfection of wastewater effluent, but a better understanding of DOM spectroscopic and photochemical properties and how they are impacted by different unit process wetlands is needed to inform design. The goals of this study were: (1) to investigate whether DOM isolates realistically represent the photochemistry of the source DOM in its original water and (2) to observe how changes of DOM along a treatment wetland affect its photochemistry, including pathogen inactivation. A pilot scale unit process wetland was studied that consisted of three different cells (open water, cattail, and bulrush) fed by secondary wastewater effluent. DOM was isolated using solid-phase extraction (SPE), photochemically characterized, and compared to the original water samples and standard DOMs. For MS2 coliphage, a virus indicator, the most efficient photosensitizer was the wastewater DOM isolated from the influent of the wetland, while for the bacterial indicator Enterococcus faecalis, inactivation results were comparable across wetland isolates. SPE resulted in isolation of 47% to 59% of whole water DOM and enriched for colored DOM. Singlet oxygen precursors were efficiently isolated, while some excited triplet state precursors remained in the extraction discharge. DOM processing indicators such as SUVA254, SUVA280, and spectral slopes including E2/ E3 ratios were reflected in the isolates. Photoinactivation of MS2 was significantly lower in both the reconstituted water samples and isolates compared to the original water sample, possibly due to disturbance of the trans-molecular integrity of DOM molecules by SPE that affects distance between MS2 and DOM sites with locally higher singlet oxygen production. For E. faecalis, results were similar in original water samples and isolates. Higher sorption of DOM to E. faecalis was roughly correlated with higher photoinactivation rates. To enhance sunlight disinfection in unit process wetlands, there is no advantage to placing open water cells after vegetated cells, as passage through the vegetated cells led to increased light absorption and lower singlet oxygen and triplet-state quantum yields and steady state concentrations.
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Affiliation(s)
- Jannis Wenk
- Department of Civil & Environmental Engineering , University of California , Berkeley , California 94720-1710 , United States
- Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt) Engineering Research Center (ERC) , University of California , Berkeley , California 94720-1710 , United States
| | - Mi T Nguyen
- Department of Civil & Environmental Engineering , University of California , Berkeley , California 94720-1710 , United States
- Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt) Engineering Research Center (ERC) , University of California , Berkeley , California 94720-1710 , United States
| | - Kara L Nelson
- Department of Civil & Environmental Engineering , University of California , Berkeley , California 94720-1710 , United States
- Re-Inventing the Nation's Urban Water Infrastructure (ReNUWIt) Engineering Research Center (ERC) , University of California , Berkeley , California 94720-1710 , United States
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Silverman AI, Tay N, Machairas N. Comparison of biological weighting functions used to model endogenous sunlight inactivation rates of MS2 coliphage. WATER RESEARCH 2019; 151:439-446. [PMID: 30639729 DOI: 10.1016/j.watres.2018.12.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 12/05/2018] [Accepted: 12/06/2018] [Indexed: 05/20/2023]
Abstract
Sunlight inactivation is important for disinfection of viruses in sunlit waters. As such, attempts have been made to predict the endogenous photoinactivation rate of bacteriophage MS2 using biological weighting functions, which describe microorganism sensitivity to sunlight inactivation as a function of wavelength. In this study, four biological weighting function models were compared to assess their ability to predict endogenous inactivation rates (kendo) of MS2. Previously-published and newly-collected datasets consisting of an incident irradiance spectrum (used as an input to the model) and a measured inactivation rate (kobs) were used for model validation and comparison. kendo values predicted by each model were compared with measured kobs to evaluate the ability of each biological weighting function to predict endogenous sunlight inactivation rates. A model previously developed by Mattle et al. (Env. Sci. Technol. 49, 334-342) over-predicted inactivation rates, whereas the other three models - a model from Fisher et al. (Env. Sci. Technol. 45, 9249-9255), a new model developed in this study, and a modification of the model by Mattle et al. (developed as part of this study) - were better able to estimate inactivation rates. The biological relevance of the spectral shape of each biological weighting function is discussed.
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Affiliation(s)
- Andrea I Silverman
- New York University, Tandon School of Engineering, Department of Civil & Urban Engineering, Brooklyn, NY, 11201, USA; New York University, College of Global Public Health, New York, NY, 10003, USA.
| | - Nerissa Tay
- New York University, Tandon School of Engineering, Department of Civil & Urban Engineering, Brooklyn, NY, 11201, USA
| | - Nikolaos Machairas
- New York University, Tandon School of Engineering, Department of Civil & Urban Engineering, Brooklyn, NY, 11201, USA
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12
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Sulzberger B, Austin AT, Cory RM, Zepp RG, Paul ND. Solar UV radiation in a changing world: roles of cryosphere-land-water-atmosphere interfaces in global biogeochemical cycles. Photochem Photobiol Sci 2019; 18:747-774. [PMID: 30810562 PMCID: PMC7418111 DOI: 10.1039/c8pp90063a] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 12/19/2018] [Indexed: 12/29/2022]
Abstract
Global change influences biogeochemical cycles within and between environmental compartments (i.e., the cryosphere, terrestrial and aquatic ecosystems, and the atmosphere). A major effect of global change on carbon cycling is altered exposure of natural organic matter (NOM) to solar radiation, particularly solar UV radiation. In terrestrial and aquatic ecosystems, NOM is degraded by UV and visible radiation, resulting in the emission of carbon dioxide (CO2) and carbon monoxide, as well as a range of products that can be more easily degraded by microbes (photofacilitation). On land, droughts and land-use change can reduce plant cover causing an increase in exposure of plant litter to solar radiation. The altered transport of soil organic matter from terrestrial to aquatic ecosystems also can enhance exposure of NOM to solar radiation. An increase in emission of CO2 from terrestrial and aquatic ecosystems due to the effects of global warming, such as droughts and thawing of permafrost soils, fuels a positive feedback on global warming. This is also the case for greenhouse gases other than CO2, including methane and nitrous oxide, that are emitted from terrestrial and aquatic ecosystems. These trace gases also have indirect or direct impacts on stratospheric ozone concentrations. The interactive effects of UV radiation and climate change greatly alter the fate of synthetic and biological contaminants. Contaminants are degraded or inactivated by direct and indirect photochemical reactions. The balance between direct and indirect photodegradation or photoinactivation of contaminants is likely to change with future changes in stratospheric ozone, and with changes in runoff of coloured dissolved organic matter due to climate and land-use changes.
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Affiliation(s)
- B Sulzberger
- Eawag: Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, Switzerland.
| | - A T Austin
- Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA) and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Agronomía, Universidad de Buenos Aires en las afiliations, Buenos Aires, Argentina
| | - R M Cory
- University of Michigan, Earth & Environmental Science, Ann Arbor, Michigan, USA
| | - R G Zepp
- United States Environmental Protection Agency, Athens, Georgia, USA
| | - N D Paul
- Lancaster Environment Centre, Lancaster University, LA1 4YQ, UK
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13
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McClary JS, Ramos NA, Boehm AB. Photoinactivation of uncultured, indigenous enterococci. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2019; 21:104-112. [PMID: 30525134 DOI: 10.1039/c8em00443a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Enterococci are used to monitor recreational water quality worldwide, so understanding their fate and transport in the environment is essential to the protection of human health. As such, researchers have documented enterococci inactivation under various exposure conditions and in diverse water matrices. However, the majority of studies have been performed using lab-cultured bacteria, which are distinct from indigenous, uncultured bacteria found in the environment. Here we investigate the photoinactivation of indigenous, uncultured enterococci from a range of sources, including wastewater treatment plants (WWTPs), marine beaches, urban streams, and a wastewater-influenced pond. We concentrated indigenous enterococci from their sources using filtration and centrifugation, placed them in a clear buffer solution, and then exposed them to simulated sunlight to measure their photoinactivation rates. First order decay rate constants (k) of indigenous, uncultured enterococci spanned an order of magnitude, from 0.3 to 2.3 m2 kJUVB-1. k values of indigenous enterococci from WWTPs tended to be larger than those from surface waters. The k value of lab-cultured Enterococcus faecalis was larger than those of indigenous, uncultured enterococci from most sources. Negative associations between the fraction of pigmented enterococci and sunlight susceptibility were observed. This work suggests that caution should be taken when extending results on bacterial photoinactivation obtained using lab-cultured bacteria to environmental bacteria, and that enterococci pigmentation may be a useful metric for estimating photoinactivation rate constants.
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Affiliation(s)
- Jill S McClary
- Civil & Environmental Engineering, Stanford University, Stanford, CA, USA.
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14
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Shoults DC, Ashbolt NJ. Decreased efficacy of UV inactivation of Staphylococcus aureus after multiple exposure and growth cycles. Int J Hyg Environ Health 2019; 222:111-116. [DOI: 10.1016/j.ijheh.2018.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 08/14/2018] [Accepted: 08/14/2018] [Indexed: 10/28/2022]
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15
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Madronich S, Björn LO, McKenzie RL. Solar UV radiation and microbial life in the atmosphere. Photochem Photobiol Sci 2018; 17:1918-1931. [PMID: 29978175 DOI: 10.1039/c7pp00407a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Many microorganisms are alive while suspended in the atmosphere, and some seem to be metabolically active during their time there. One of the most important factors threatening their life and activity is solar ultraviolet (UV) radiation. Quantitative understanding of the spatial and temporal survival patterns in the atmosphere, and of the ultimate deposition of microbes to the surface, is limited by a number factors some of which are discussed here. These include consideration of appropriate spectral sensitivity functions for biological damage (e.g. inactivation), and the estimation of UV radiation impingent on a microorganism suspended in the atmosphere. We show that for several bacteria (E. coli, S. typhimurium, and P. acnes) the inactivation rates correlate well with irradiances weighted by the DNA damage spectrum in the UV-B spectral range, but when these organisms show significant UV-A (or visible) sensitivities, the correlations become clearly non-linear. The existence of these correlations enables the use of a single spectrum (here DNA damage) as a proxy for sensitivity spectra of other biological effects, but with some caution when the correlations are strongly non-linear. The radiative quantity relevant to the UV exposure of a suspended particle is the fluence rate at an altitude above ground, while down-welling irradiance at ground-level is the quantity most commonly measured or estimated in satellite-derived climatologies. Using a radiative transfer model that computes both quantities, we developed a simple parameterization to exploit the much larger irradiance data bases to estimate fluence rates, and present the first fluence-rate based climatology of DNA-damaging UV radiation in the atmosphere. The estimation of fluence rates in the presence of clouds remains a particularly challenging problem. Here we note that both reductions and enhancements in the UV radiation field are possible, depending mainly on cloud optical geometry and prevailing solar zenith angles. These complex effects need to be included in model simulations of the atmospheric life cycle of the organisms.
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16
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Scoullos IM, Lopez Vazquez CM, van de Vossenberg J, Hammond M, Brdjanovic D. Effect of Artificial Solar Radiation on the Die-Off of Pathogen Indicator Organisms in Urban Floods. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH 2018; 13:107-116. [PMID: 30873212 PMCID: PMC6383957 DOI: 10.1007/s41742-018-0160-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 10/04/2018] [Accepted: 11/12/2018] [Indexed: 05/26/2023]
Abstract
In the last decade, flooding has caused the death of over 60,000 people and affected over 900 million people globally. This is expected to increase as a result of climate change, increased populations and urbanisation. Floods can cause infections due to the release of water-borne pathogenic microorganisms from surcharged combined sewers and other sources of fecal contamination. This research contributes to a better understanding of how the occurrence of water-borne pathogens in contaminated shallow water bodies is affected by different environmental conditions. The inactivation of fecal indicator bacteria Escherichia coli was studied in an open stirred reactor, under controlled exposure to simulated sunlight, mimicking the effect of different latitudes and seasons, and different concentrations of total suspended solids (TSS) corresponding to different levels of dilution and runoff. While attachment of bacteria on the solid particles did not take place, the decay rate coefficient, k (d-1), was found to depend on light intensity, I (W m-2), and duration of exposure to sunlight, T (h d-1), in a linear way (k = k D+ 0.03·I and k = k D+ 0.65·T, respectively) and on the concentration of TSS (mg L-1), in an inversely proportional exponential way (k = k D+ 14.57·e-0.02·[TSS] ). The first-order inactivation rate coefficient in dark conditions, k D= 0.37 d-1, represents the effect of stresses other than light. This study suggests that given the sunlight conditions during an urban flood, and the concentration of indicator organisms and TSS, the above equations can give an estimate of the fate of selected pathogens, allowing rapid implementation of appropriate measures to mitigate public health risks.
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Affiliation(s)
- I. M. Scoullos
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands
| | - C. M. Lopez Vazquez
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands
| | - J. van de Vossenberg
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands
| | - M. Hammond
- Environment and Natural Resources Global Practice, World Bank Group, Washington, DC USA
| | - D. Brdjanovic
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
- Department of Environmental Engineering and Water Technology, IHE Delft Institute for Water Education, P.O. Box 3015, 2601 DA Delft, The Netherlands
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17
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Zepp RG, Cyterski M, Wong K, Georgacopoulos O, Acrey B, Whelan G, Parmar R, Molina M. Biological Weighting Functions for Evaluating the Role of Sunlight-Induced Inactivation of Coliphages at Selected Beaches and Nearby Tributaries. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:13068-13076. [PMID: 30395707 PMCID: PMC7086407 DOI: 10.1021/acs.est.8b02191] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Coliphages can indicate contamination of recreational waters and previous studies show that sunlight is important in altering densities of coliphages, other indicator microorganisms, and pathogens in aquatic environments. Here, we report on laboratory studies of light-induced inactivation of two coliphage groups-male-specific (F+) and somatic coliphage-under various conditions in phosphate-buffered water (PBW). Strains isolated from wastewater treatment facilities and laboratory strains (MS2 and phiX174 coliphages) were evaluated. Inactivation rates were determined in a series of irradiations using simulated solar radiation passed through light filters that blocked different parts of the ultraviolet spectral region. Inactivation rates and spectral irradiance from these experiments were then analyzed to develop biological weighting functions (BWFs) for the light-induced inactivation. BWFs were used to model the inactivation of coliphages over a range of conditions in aquatic environments that included two beach sites in Lake Michigan and one in Lake Erie. For example, modeled effects of sunlight attenuation, using UV absorption data from the three Great Lakes beach sites, inferred that direct photoinactivation rate constants, averaged over a one-meter water column in swimmable areas, were reduced 2- to 5-fold, compared to near-surface rate constants.
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Affiliation(s)
- Richard G Zepp
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Michael Cyterski
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Kelvin Wong
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Ourania Georgacopoulos
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Brad Acrey
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Gene Whelan
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Rajbir Parmar
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
| | - Marirosa Molina
- U.S. Environmental Protection Agency, National Exposure Research Laboratory , 960 College Station Road , Athens , Georgia 30605 , United States
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18
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Uyguner Demirel CS, Birben NC, Bekbolet M. A comprehensive review on the use of second generation TiO 2 photocatalysts: Microorganism inactivation. CHEMOSPHERE 2018; 211:420-448. [PMID: 30077938 DOI: 10.1016/j.chemosphere.2018.07.121] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 07/04/2018] [Accepted: 07/21/2018] [Indexed: 05/12/2023]
Abstract
Photocatalytic disinfection practices have been applied for decades and attract current interest along with the developments in synthesis of novel photocatalysts. A survey based investigation was performed for elucidation of photocatalytic treatment details as well as disinfection mechanism of microorganisms. The present work brings significant information on the utilization of second generation TiO2 photocatalysts for inactivation of microorganisms typically using E. coli as the model microorganism. Special interest was devoted to the role of organic matrix either generated during treatment or as a natural component. Studies on photocatalytic disinfection were extensively reviewed and evaluated with respect to basic operational parameters related to photocatalysis, and types and properties of microorganisms investigated. Degradation mechanism and behavior of microorganisms towards reactive oxygen species during disinfection and organic matrix effects were also addressed. For successful utilization and effective assessment of visible light active photocatalysts, standard protocols for disinfection activity testing have to be set. Further improvement of the efficiency of these materials would be promising for future applications in water treatment processes.
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Affiliation(s)
| | - Nazmiye Cemre Birben
- Bogazici University, Institute of Environmental Sciences, 34342, Bebek, Istanbul, Turkey.
| | - Miray Bekbolet
- Bogazici University, Institute of Environmental Sciences, 34342, Bebek, Istanbul, Turkey.
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19
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Nelson KL, Boehm AB, Davies-Colley RJ, Dodd MC, Kohn T, Linden KG, Liu Y, Maraccini PA, McNeill K, Mitch WA, Nguyen TH, Parker KM, Rodriguez RA, Sassoubre LM, Silverman AI, Wigginton KR, Zepp RG. Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2018; 20:1089-1122. [PMID: 30047962 PMCID: PMC7064263 DOI: 10.1039/c8em00047f] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
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 sunlight-mediated 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.
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Affiliation(s)
- Kara L Nelson
- Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
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Climate change-induced increases in precipitation are reducing the potential for solar ultraviolet radiation to inactivate pathogens in surface waters. Sci Rep 2017; 7:13033. [PMID: 29026153 PMCID: PMC5638896 DOI: 10.1038/s41598-017-13392-2] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 09/22/2017] [Indexed: 11/09/2022] Open
Abstract
Climate change is accelerating the release of dissolved organic matter (DOM) to inland and coastal waters through increases in precipitation, thawing of permafrost, and changes in vegetation. Our modeling approach suggests that the selective absorption of ultraviolet radiation (UV) by DOM decreases the valuable ecosystem service wherein sunlight inactivates waterborne pathogens. Here we highlight the sensitivity of waterborne pathogens of humans and wildlife to solar UV, and use the DNA action spectrum to model how differences in water transparency and incident sunlight alter the ability of UV to inactivate waterborne pathogens. A case study demonstrates how heavy precipitation events can reduce the solar inactivation potential in Lake Michigan, which provides drinking water to over 10 million people. These data suggest that widespread increases in DOM and consequent browning of surface waters reduce the potential for solar UV inactivation of pathogens, and increase exposure to infectious diseases in humans and wildlife.
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21
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Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure. Appl Environ Microbiol 2017. [PMID: 28646114 DOI: 10.1128/aem.01052-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sunlight influences microbial water quality of surface waters. Previous studies have investigated photoinactivation mechanisms and cellular photostress responses of fecal indicator bacteria (FIB), including Escherichia coli and enterococci, but further work is needed to characterize photostress responses of bacterial pathogens. Here we investigate the photoinactivation of Staphylococcus aureus (strain Newman), a pigmented, waterborne pathogen of emerging concern. We measured photodecay using standard culture-based assays and cellular membrane integrity and investigated photostress response by measuring the relative number of mRNA transcripts of select oxidative stress, DNA repair, and metabolism genes. Photoinactivation experiments were performed in both oxic and anoxic systems to further investigate the role of oxygen-mediated and non-oxygen-mediated photoinactivation mechanisms. S. aureus lost culturability much faster in oxic systems than in anoxic systems, indicating an important role for oxygen in photodecay mechanisms. S. aureus cell membranes were damaged by sunlight exposure in anoxic systems but not in oxic systems, as measured by cell membrane permeability to propidium iodide. After sunlight exposure, S. aureus increased expression of a gene coding for methionine sulfoxide reductase after 12 h of sunlight exposure in the oxic system and after 6 h of sunlight exposure in the anoxic system, suggesting that methionine sulfoxide reductase is an important enzyme for defense against both oxygen-dependent and oxygen-independent photostresses. This research highlights the importance of oxygen in bacterial photoinactivation in environmentally relevant systems and the complexity of the bacterial photostress response with respect to cell structure and transcriptional regulation.IMPORTANCEStaphylococcus aureus is a pathogenic bacterium that causes gastrointestinal, respiratory, and skin infections. In severe cases, S. aureus infection can lead to life-threatening diseases, including pneumonia and sepsis. Cases of community-acquired S. aureus infection have been increasing in recent years, pointing to the importance of considering S. aureus transmission pathways outside the hospital environment. Associations have been observed between recreational water contact and staphylococcal skin infections, suggesting that recreational waters may be an important environmental transmission pathway for S. aureus However, prediction of human health risk in recreational waters is hindered by incomplete knowledge of pathogen sources, fate, and transport in this environment. This study is an in-depth investigation of the inactivation of a representative strain of S. aureus by sunlight exposure, one of the most important factors controlling the fate of microbial contaminants in clear waters, which will improve our ability to predict water quality changes and human health risk in recreational waters.
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