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Knappett PSK, Du J, Liu P, Horvath V, Mailloux BJ, Feighery J, van Geen A, Culligan PJ. Importance of Reversible Attachment in Predicting E. Coli Transport in Saturated Aquifers From Column Experiments. Adv Water Resour 2014; 63:120-130. [PMID: 24821993 PMCID: PMC4014781 DOI: 10.1016/j.advwatres.2013.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Drinking water wells indiscriminatingly placed adjacent to fecal contaminated surface water represents a significant but difficult to quantify health risk. Here we seek to understand mechanisms that limit the contamination extent by scaling up bacterial transport results from the laboratory to the field in a well constrained setting. Three pulses of E. coli originating during the early monsoon from a freshly excavated pond receiving latrine effluent in Bangladesh were monitored in 6 wells and modeled with a two-dimensional (2-D) flow and transport model conditioned with measured hydraulic heads. The modeling was performed assuming three different modes of interaction of E. coli with aquifer sands: 1) irreversible attachment only (best-fit ki=7.6 day-1); 2) reversible attachment only (ka=10.5 and kd=0.2 day-1); and 3) a combination of reversible and irreversible modes of attachment (ka=60, kd=7.6, ki=5.2 day-1). Only the third approach adequately reproduced the observed temporal and spatial distribution of E. coli, including a 4-log10 lateral removal distance of ∼9 m. In saturated column experiments, carried out using aquifer sand from the field site, a combination of reversible and irreversible attachment was also required to reproduce the observed breakthrough curves and E. coli retention profiles within the laboratory columns. Applying the laboratory-measured kinetic parameters to the 2-D calibrated flow model of the field site underestimates the observed 4-log10 lateral removal distance by less than a factor of two. This is promising for predicting field scale transport from laboratory experiments.
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Affiliation(s)
- P. S. K. Knappett
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964
| | - J. Du
- Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
| | - P. Liu
- Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
| | - V. Horvath
- Department of Environmental Science, Barnard College, New York, NY 10027
| | - B. J. Mailloux
- Department of Environmental Science, Barnard College, New York, NY 10027
| | - J. Feighery
- Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
| | - A. van Geen
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964
| | - P. J. Culligan
- Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027
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Feighery J, Mailloux BJ, Ferguson A, Ahmed KM, van Geen A, Culligan PJ. Transport of E. coli in Aquifer Sediments of Bangladesh: Implications for Widespread Microbial Contamination of Groundwater. Water Resour Res 2013; 49:3897-3911. [PMID: 24653543 PMCID: PMC3956056 DOI: 10.1002/wrcr.20289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Fecal bacteria are frequently found at much greater distances than would be predicted by laboratory studies, indicating that improved models that incorporate more complexity are might be needed to explain the widespread contamination of many shallow aquifers. In this study, laboratory measurements of breakthrough and retained bacteria in columns of intact and repacked sediment cores from Bangladesh were fit using a two-population model with separate reversible and irreversible attachment sites that also incorporated bacterial decay rates. Separate microcosms indicated an average first order decay rate of 0.03 log10 / day for free bacteria in both the liquid phase and bacteria attached to the solid phase. Although two-thirds of the column results could be well fit with a dual deposition site, single population model, fitting of one third of the results required a two-population model with a high irreversible attachment rate (between 5 and 60 hr-1) for one population of bacteria and a much lower rate (from 5 hr-1 to essentially zero) for the second. Inferred attachment rates for the reversible sites varied inversely with grain size (varying from 1 - 20 hr-1 for grain sizes between 0.1 and 0.3 mm) while reversible detachment rates were found to be nearly constant (approximately 0.5 hr-1). Field simulations based on the fitted two-population model parameters predict only a two-fold reduction in fecal source concentration over a distance of 10 m, determined primarily by the decay rate of the bacteria. The existence of a secondary population of bacteria with a low attachment rate might help explain the observed widespread contamination of tubewell water with E. coli at the field site where the cores were collected, as well as other similar sites.
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Affiliation(s)
- John Feighery
- Department of Earth and Environmental Engineering, Columbia University, New York, USA
| | - Brian J. Mailloux
- Department of Environmental Sciences, Barnard College, New York, USA
| | - A.S. Ferguson
- Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, USA
| | | | - Alexander van Geen
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA
| | - Patricia J. Culligan
- Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, USA
- corresponding author: Room 626 SW Mudd Building, 500 West 120 Street, New York, NY 10027, USA, tel: +1 212 854 3154;
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Ferguson AS, Layton AC, Mailloux BJ, Culligan PJ, Williams DE, Smartt AE, Sayler GS, Feighery J, McKay LD, Knappett PSK, Alexandrova E, Arbit T, Emch M, Escamilla V, Ahmed KM, Alam MJ, Streatfield PK, Yunus M, van Geen A. Comparison of fecal indicators with pathogenic bacteria and rotavirus in groundwater. Sci Total Environ 2012; 431:314-22. [PMID: 22705866 PMCID: PMC3587152 DOI: 10.1016/j.scitotenv.2012.05.060] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/16/2012] [Accepted: 05/17/2012] [Indexed: 04/15/2023]
Abstract
Groundwater is routinely analyzed for fecal indicators but direct comparisons of fecal indicators to the presence of bacterial and viral pathogens are rare. This study was conducted in rural Bangladesh where the human population density is high, sanitation is poor, and groundwater pumped from shallow tubewells is often contaminated with fecal bacteria. Five indicator microorganisms (E. coli, total coliform, F+RNA coliphage, Bacteroides and human-associated Bacteroides) and various environmental parameters were compared to the direct detection of waterborne pathogens by quantitative PCR in groundwater pumped from 50 tubewells. Rotavirus was detected in groundwater filtrate from the largest proportion of tubewells (40%), followed by Shigella (10%), Vibrio (10%), and pathogenic E. coli (8%). Spearman rank correlations and sensitivity-specificity calculations indicate that some, but not all, combinations of indicators and environmental parameters can predict the presence of pathogens. Culture-dependent fecal indicator bacteria measured on a single date did not predict total bacterial pathogens, but annually averaged monthly measurements of culturable E. coli did improve prediction for total bacterial pathogens. A qPCR-based E. coli assay was the best indicator for the bacterial pathogens. F+RNA coliphage were neither correlated nor sufficiently sensitive towards rotavirus, but were predictive of bacterial pathogens. Since groundwater cannot be excluded as a significant source of diarrheal disease in Bangladesh and neighboring countries with similar characteristics, the need to develop more effective methods for screening tubewells with respect to microbial contamination is necessary.
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Affiliation(s)
- Andrew S Ferguson
- Department of Civil Engineering and Engineering Mechanics, Columbia University, NY, USA.
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Wu J, van Geen A, Ahmed KM, Alam YAJ, Culligan PJ, Escamilla V, Feighery J, Ferguson AS, Knappett P, Mailloux BJ, McKay LD, Serre ML, Streatfield PK, Yunus M, Emch M. Increase in diarrheal disease associated with arsenic mitigation in Bangladesh. PLoS One 2011; 6:e29593. [PMID: 22216326 PMCID: PMC3247276 DOI: 10.1371/journal.pone.0029593] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 12/01/2011] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Millions of households throughout Bangladesh have been exposed to high levels of arsenic (As) causing various deadly diseases by drinking groundwater from shallow tubewells for the past 30 years. Well testing has been the most effective form of mitigation because it has induced massive switching from tubewells that are high (>50 µg/L) in As to neighboring wells that are low in As. A recent study has shown, however, that shallow low-As wells are more likely to be contaminated with the fecal indicator E. coli than shallow high-As wells, suggesting that well switching might lead to an increase in diarrheal disease. METHODS Approximately 60,000 episodes of childhood diarrhea were collected monthly by community health workers between 2000 and 2006 in 142 villages of Matlab, Bangladesh. In this cross-sectional study, associations between childhood diarrhea and As levels in tubewell water were evaluated using logistic regression models. RESULTS Adjusting for wealth, population density, and flood control by multivariate logistic regression, the model indicates an 11% (95% confidence intervals (CIs) of 4-19%) increase in the likelihood of diarrhea in children drinking from shallow wells with 10-50 µg/L As compared to shallow wells with >50 µg/L As. The same model indicates a 26% (95%CI: 9-42%) increase in diarrhea for children drinking from shallow wells with ≤10 µg/L As compared to shallow wells with >50 µg/L As. CONCLUSION Children drinking water from shallow low As wells had a higher prevalence of diarrhea than children drinking water from high As wells. This suggests that the health benefits of reducing As exposure may to some extent be countered by an increase in childhood diarrhea.
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Affiliation(s)
- Jianyong Wu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Alexander van Geen
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York, United States of America
| | | | - Yasuyuki Akita Jahangir Alam
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Geology, University of Dhaka, Dhaka, Bangladesh
| | - Patricia J. Culligan
- Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York, United States of America
| | - Veronica Escamilla
- Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - John Feighery
- Department of Earth and Environmental Engineering, Columbia University, New York, New York, United States of America
| | - Andrew S. Ferguson
- Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York, United States of America
| | - Peter Knappett
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Brian J. Mailloux
- Department of Environmental Sciences, Barnard College, New York, New York, United States of America
| | - Larry D. McKay
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Marc L. Serre
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | | | - Mohammad Yunus
- International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Michael Emch
- Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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van Geen A, Ahmed KM, Akita Y, Alam MJ, Culligan PJ, Emch M, Escamilla V, Feighery J, Ferguson AS, Knappett P, Layton AC, Mailloux BJ, McKay LD, Mey JL, Serre ML, Streatfield PK, Wu J, Yunus M. Fecal contamination of shallow tubewells in Bangladesh inversely related to arsenic. Environ Sci Technol 2011; 45:1199-205. [PMID: 21226536 PMCID: PMC3037737 DOI: 10.1021/es103192b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The health risks of As exposure due to the installation of millions of shallow tubewells in the Bengal Basin are known, but fecal contamination of shallow aquifers has not systematically been examined. This could be a source of concern in densely populated areas with poor sanitation because the hydraulic travel time from surface water bodies to shallow wells that are low in As was previously shown to be considerably shorter than for shallow wells that are high in As. In this study, 125 tubewells 6-36 m deep were sampled in duplicate for 18 months to quantify the presence of the fecal indicator Escherichia coli. On any given month, E. coli was detected at levels exceeding 1 most probable number per 100 mL in 19-64% of all shallow tubewells, with a higher proportion typically following periods of heavy rainfall. The frequency of E. coli detection averaged over a year was found to increase with population surrounding a well and decrease with the As content of a well, most likely because of downward transport of E. coli associated with local recharge. The health implications of higher fecal contamination of shallow tubewells, to which millions of households in Bangladesh have switched in order to reduce their exposure to As, need to be evaluated.
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Affiliation(s)
- Alexander van Geen
- Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
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