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de Brito Cruz D, Schmidt PJ, Emelko MB. Drinking water QMRA and decision-making: Sensitivity of risk to common independence assumptions about model inputs. WATER RESEARCH 2024; 259:121877. [PMID: 38870891 DOI: 10.1016/j.watres.2024.121877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 05/31/2024] [Accepted: 06/02/2024] [Indexed: 06/15/2024]
Abstract
When assessing risk posed by waterborne pathogens in drinking water, it is common to use Monte Carlo simulations in Quantitative Microbial Risk Assessment (QMRA). This method accounts for the variables that affect risk and their different values in a given system. A common underlying assumption in such analyses is that all random variables are independent (i.e., one is not associated in any way with another). Although the independence assumption simplifies the analysis, it is not always correct. For example, treatment efficiency can depend on microbial concentrations if changes in microbial concentrations either affect treatment themselves or are associated with water quality changes that affect treatment (e.g., during/after climate shocks like extreme precipitation events or wildfires). Notably, the effects of erroneous assumptions of independence in QMRA have not been widely discussed. Due to the implications of drinking water safety decisions on public health protection, it is critical that risk models accurately reflect the context being studied to meaningfully support decision-making. This work illustrates how dependence between pathogen concentration and either treatment efficiency or water consumption can impact risk estimates using hypothetical scenarios of relevance to drinking water QMRA. It is shown that the mean and variance of risk estimates can change substantially with different degrees of correlation. Data from a water supply system in Calgary, Canada are also used to illustrate the effect of dependence on risk. Recognizing the difficulty of obtaining data to empirically assess dependence, a framework to guide evaluation of the effect of dependence is presented to enhance support for decision making. This work emphasizes the importance of acknowledging and discussing assumptions implicit to models.
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Affiliation(s)
- Dafne de Brito Cruz
- Department of Civil and Environmental Engineering, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada.
| | - Philip J Schmidt
- Department of Civil and Environmental Engineering, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada.
| | - Monica B Emelko
- Department of Civil and Environmental Engineering, University of Waterloo, 200 University Ave. W, Waterloo, Ontario N2L 3G1, Canada.
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Hadi M, Bashardoust P, Solaimany Aminabad M, Nazmara S, Rezvani Ghalhari M, Mesdaghinia A, Hemmati Borji S. Exposure assessment of nitrate and phenol derivatives in Tehran's water distribution system. JOURNAL OF WATER AND HEALTH 2024; 22:147-168. [PMID: 38295078 PMCID: wh_2023_133 DOI: 10.2166/wh.2023.133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
The presence of organic and inorganic contaminants in drinking water is a global concern. Nitrate and phenol derivatives are examples of pollutants that could be of anthropogenic origin. They are associated with numerous health risks, underscoring the importance of monitoring their presence in drinking water. This study aimed to measure nitrate and phenol derivatives, including 2,4-Dichlorophenol (2,4-DCP), Pentachlorophenol (PCP), 2,4,5-Trichlorophenol (2,4,5-TCP), 2-Chlorophenol (2-CP), 4-Chlorophenol (4-CP), and phenol, in Tehran's water distribution system (WDS). The pollutants in Tehran's WDS were significantly and positively correlated with precipitation. The Hazard Quotient (HQ) and the Excess Lifetime Cancer Risk (ELCR) of the detected pollutants were estimated. The results showed that the regional mean of nitrate and PCP in Tehran's WDS were 35.58±8.71mg L-1 and 76.14±16.93 ng L-1 lower than the guideline values of 50 mg L-1 and 1000 ng L-1, respectively. Some districts exhibited nitrate concentration exceeding the allowable limit by a factor of 1.2 to 2.3. Consequently, the nitrate intake in some districts constituted approximately 50% of the reference dose. While PCP as a phenol derivative with more health concerns was identified in Tehran's WDS, the likelihood of its health effects was determined to be negligible.
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Affiliation(s)
- Mahdi Hadi
- Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran E-mail: ;
| | - Parnia Bashardoust
- Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mehri Solaimany Aminabad
- Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran
| | - Shahrokh Nazmara
- Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran; Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Rezvani Ghalhari
- Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Alireza Mesdaghinia
- Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran; Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Saeedeh Hemmati Borji
- Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran
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Bhatt A, Dada AC, Prajapati SK, Arora P. Integrating life cycle assessment with quantitative microbial risk assessment for a holistic evaluation of sewage treatment plant. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 862:160842. [PMID: 36509266 DOI: 10.1016/j.scitotenv.2022.160842] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 11/12/2022] [Accepted: 12/07/2022] [Indexed: 06/17/2023]
Abstract
An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 kWh.day-1) contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.
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Affiliation(s)
- Ankita Bhatt
- Department of Hydro and Renewable Energy, Indian Institute of Technology Roorkee, Uttarakhand, India
| | | | - Sanjeev Kumar Prajapati
- Department of Hydro and Renewable Energy, Indian Institute of Technology Roorkee, Uttarakhand, India
| | - Pratham Arora
- Department of Hydro and Renewable Energy, Indian Institute of Technology Roorkee, Uttarakhand, India.
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Doménech E, Martorell S, Kombo-Mpindou GOM, Macián-Cervera J, Escuder-Bueno I. Risk assessment of Cryptosporidium intake in drinking water treatment plant by a combination of predictive models and event-tree and fault-tree techniques. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156500. [PMID: 35675884 DOI: 10.1016/j.scitotenv.2022.156500] [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: 01/31/2022] [Revised: 05/30/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
Risk-informed decision making permits a more effective water safety management. In this framework, this article introduces the rationale and proposes a new approach to carry out a quantitative risk assessment along the water chain, from river source to tap water, by integrating predictive modelling combined with event-tree and fault-tree techniques. The model developed by this approach could not only account for normal but also for abnormal process conditions in the water treatment plant, as well as assess the real impact of the applied safety controls, such as turbidity control. A sensitivity study was conducted to determine the effect of considering a typical drinking water treatment plant (DWTP), i.e. coagulation, sedimentation and filtration with two turbidity controls (on intake and after filtration) on the risk of infection due to exposure to Cryptosporidium in tap water. The results showed that, with the current effectiveness of turbidity reduction in the DWTP, the first control did not minimise the annual risk of Cryptosporidium infection (3.6E-04) and only limiting turbidity after filtration to below 0.01NTU provided a clear reduction in risk (7.7E-05) at the cost of rejecting 60 % of the water after the control. The lowest risk was found when turbidity reduction was set at 4 logs (8.48E-06), although this means that the effectiveness of turbidity reduction should be greatly improved. It was therefore concluded that supplementing the current treatment with alternative barriers such as UV or ozone disinfection and/or implementing direct control of Cryptosporidium concentration should be considered.
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Affiliation(s)
- E Doménech
- Instituto Universitario de Ingeniería de Alimentos para el Desarrollo, Department of Food Technology (DTA), Universitat Politècnica de València, Camino de Vera s/n, 46022, Valencia, Spain.
| | - S Martorell
- MEDASEGI Research Group, Department of Chemical and Nuclear Engineering, Universitat Politècnica de València, Camino de Vera s/n, 46022, Valencia, Spain.
| | - G O M Kombo-Mpindou
- Instituto de Ingeniería del Agua y Medio Ambiente (IIAMA), Universitat Politècnica de València, Camino de Vera s/n, 46022, Valencia, Spain.
| | - J Macián-Cervera
- Global Omnium, Gran Vïa Marqués del Turia, 19, 46005 València, Spain.
| | - I Escuder-Bueno
- Instituto de Ingeniería del Agua y Medio Ambiente (IIAMA), Universitat Politècnica de València, Camino de Vera s/n, 46022, Valencia, Spain.
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Byrne DM, Hamilton KA, Houser SA, Mubasira M, Katende D, Lohman HAC, Trimmer JT, Banadda N, Zerai A, Guest JS. Navigating Data Uncertainty and Modeling Assumptions in Quantitative Microbial Risk Assessment in an Informal Settlement in Kampala, Uganda. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:5463-5474. [PMID: 33750111 DOI: 10.1021/acs.est.0c05693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Decision-makers in developing communities often lack credible data to inform decisions related to water, sanitation, and hygiene. Quantitative microbial risk assessment (QMRA), which quantifies pathogen-related health risks across exposure routes, can be informative; however, the utility of QMRA for decision-making is often undermined by data gaps. This work integrates QMRA, uncertainty and sensitivity analyses, and household surveys in Bwaise, Kampala (Uganda) to characterize the implications of censored data management, identify sources of uncertainty, and incorporate risk perceptions to improve the suitability of QMRA for informal settlements or similar settings. In Bwaise, drinking water, hand rinse, and soil samples were collected from 45 households and supplemented with data from 844 surveys. Quantified pathogen (adenovirus, Campylobacter jejuni, and Shigella spp./EIEC) concentrations were used with QMRA to model infection risks from exposure through drinking water, hand-to-mouth contact, and soil ingestion. Health risks were most sensitive to pathogen data, hand-to-mouth contact frequency, and dose-response models (particularly C. jejuni). When managing censored data, results from upper limits of detection, half of limits of detection, and uniform distributions returned similar results, which deviated from lower limits of detection and maximum likelihood estimation imputation approaches. Finally, risk perceptions (e.g., it is unsafe to drink directly from a water source) were identified to inform risk management.
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Affiliation(s)
- Diana M Byrne
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, 3221 Newmark Civil Engineering Laboratory, Urbana, Illinois 61801, United States
| | - Kerry A Hamilton
- The School with Sustainable Engineering and the Built Environment and The Biodesign Institute Center for Environmental Health Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Stephanie A Houser
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, 3221 Newmark Civil Engineering Laboratory, Urbana, Illinois 61801, United States
| | - Muwonge Mubasira
- Community Integrated Development Initiatives, P.O. Box 764, Kampala, Uganda
| | - David Katende
- Community Integrated Development Initiatives, P.O. Box 764, Kampala, Uganda
| | - Hannah A C Lohman
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, 3221 Newmark Civil Engineering Laboratory, Urbana, Illinois 61801, United States
| | - John T Trimmer
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, 3221 Newmark Civil Engineering Laboratory, Urbana, Illinois 61801, United States
| | - Noble Banadda
- Department of Agricultural & Biosystems Engineering, Makerere University, P.O. Box 7062, Kampala, Uganda
| | - Assata Zerai
- Department of Sociology, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Jeremy S Guest
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, 3221 Newmark Civil Engineering Laboratory, Urbana, Illinois 61801, United States
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Cantoni B, Penserini L, Vries D, Dingemans MML, Bokkers BGH, Turolla A, Smeets PWMH, Antonelli M. Development of a quantitative chemical risk assessment (QCRA) procedure for contaminants of emerging concern in drinking water supply. WATER RESEARCH 2021; 194:116911. [PMID: 33607390 DOI: 10.1016/j.watres.2021.116911] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The uncertainties on the occurrence, fate and hazard of Contaminants of Emerging Concern (CECs) increasingly challenge drinking water (DW) utilities whether additional measures should be taken to reduce the health risk. This has led to the development and evaluation of risk-based approaches by the scientific community. DW guideline values are commonly derived based on deterministic chemical risk assessment (CRA). Here, we propose a new probabilistic procedure, that is a quantitative chemical risk assessment (QCRA), to assess potential health risk related to the occurrence of CECs in DW. The QCRA includes uncertainties in risk calculation in both exposure and hazard assessments. To quantify the health risk in terms of the benchmark quotient probabilistic distribution, the QCRA estimates the probabilistic distribution of CECs concentration in DW based on their concentration in source water and simulating the breakthrough curves of a granular activated carbon (GAC) treatment process. The model inputs and output uncertainties were evaluated by sensitivity and uncertainty analyses for each step of the risk assessment to identify the most relevant factors affecting risk estimation. Dominant factors resulted to be the concentration of CECs in water sources, GAC isotherm parameters and toxicological data. To stress the potential of this new QCRA approach, several case studies are considered with focus on bisphenol A as an example CEC and various GAC management options. QCRA quantifies the probabilistic risk, providing more insight compared to CRA. QCRA proved to be more effective in supporting the intervention prioritization for treatment optimization to pursue health risk minimization.
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Affiliation(s)
- Beatrice Cantoni
- Politecnico Milano, Department of Civil and Environmental Engineering (DICA) - Environmental Section, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Luca Penserini
- Politecnico Milano, Department of Civil and Environmental Engineering (DICA) - Environmental Section, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Dirk Vries
- KWR, Groningenhaven 7, 3433 PE Nieuwegein, The Netherlands
| | - Milou M L Dingemans
- KWR, Groningenhaven 7, 3433 PE Nieuwegein, The Netherlands; Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands
| | - Bas G H Bokkers
- National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
| | - Andrea Turolla
- Politecnico Milano, Department of Civil and Environmental Engineering (DICA) - Environmental Section, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | | | - Manuela Antonelli
- Politecnico Milano, Department of Civil and Environmental Engineering (DICA) - Environmental Section, Piazza Leonardo da Vinci 32, 20133 Milano, Italy.
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Owens CEL, Angles ML, Cox PT, Byleveld PM, Osborne NJ, Rahman MB. Implementation of quantitative microbial risk assessment (QMRA) for public drinking water supplies: Systematic review. WATER RESEARCH 2020; 174:115614. [PMID: 32087414 DOI: 10.1016/j.watres.2020.115614] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Revised: 02/02/2020] [Accepted: 02/10/2020] [Indexed: 05/04/2023]
Abstract
In the more than 15 years since its introduction, quantitative microbial risk assessment (QMRA) has become a widely used technique for assessing population health risk posed by waterborne pathogens. However, the variation in approaches taken for QMRA in relation to drinking water supply is not well understood. This systematic review identifies, categorises, and critically synthesises peer-reviewed and academic case studies of QMRA implementation for existing distributed public drinking water supplies. Thirty-nine English-language, peer-reviewed and academic studies published from 2003 to 2019 were identified. Key findings were synthesised in narrative form. The overall designs of the included studies varied widely, as did the assumptions used in risk calculation, especially in relation to pathogen dose. There was also substantial variation in the degree to which the use of location-specific data weighed with the use of assumptions when performing risk calculation. In general, the included studies' complexity did not appear to be associated with greater result certainty. Factors relating to pathogen dose were commonly influential on risk estimates whereas dose-response parameters tended to be of low relative influence. In two of the included studies, use of the 'susceptible fraction' factor was inconsistent with recognised guidance and potentially led to the underestimation of risk. While approaches and assumptions used in QMRA need not be standardised, improvement in the reporting of QMRA results and uncertainties would be beneficial. It is recommended that future authors consider the water supply QMRA reporting checklist developed for the current review. Consideration of the broad types of uncertainty relevant to QMRA is also recommended. Policy-makers should consider emergent discussion on acute microbial health-based targets when setting normative guidelines. The continued representation of QMRA case studies within peer-reviewed and academic literature would also enhance future implementation. Further research is needed on the optimisation of QMRA resourcing given the application context.
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Affiliation(s)
- Christopher E L Owens
- School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Kensington NSW 2052, Australia; Sydney Water Corporation, Parramatta NSW 2124, Australia.
| | - Mark L Angles
- Water Angles Consulting, Vaucluse NSW 2030, Australia
| | - Peter T Cox
- Sydney Water Corporation, Parramatta NSW 2124, Australia
| | | | - Nicholas J Osborne
- School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Kensington NSW 2052, Australia; School of Public Health, Faculty of Medicine, University of Queensland, Herston QLD 4006, Australia; European Centre for Environment and Human Health, University of Exeter, Royal Cornwall Hospital, Truro TR1 3HD, United Kingdom
| | - Md Bayzid Rahman
- School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Kensington NSW 2052, Australia
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