Importance of reversible attachment in predicting E. coli transport in saturated aquifers from column experiments |
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| Institution: | 1. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, United States;2. Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027, United States;3. Department of Environmental Science, Barnard College, New York, NY 10027, United States;1. B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, Nauky Ave., 47, 61103 Kharkiv, Ukraine;2. Institute of Organic Chemistry of Research Centre for Natural Sciences of the Hungarian Academy of Sciences, Magyar Tudosok Korutja, 2, Budapest H-1117, Hungary;3. Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA;1. School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ireland;2. Environmental Health and Sustainability Institute, Dublin Institute of Technology, Dublin, Ireland;3. Department of Biological Sciences, University of Limerick, Limerick, Ireland;4. Department of Chemical Sciences, University of Limerick, Limerick, Ireland;1. Independent Consultant, Cambridge, UK;2. International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh;3. Bangladesh Water Development Board, Green Road, Dhaka, Bangladesh;4. Dhaka University of Engineering and Technology, Shimultoly Road, Gazipur, Bangladesh;5. Department of Soil, Water & Environment, University of Dhaka, Dhaka, 1000, Bangladesh;6. WaterAid Bangladesh, House 97/B, Road No 25, Block A, Banani, Dhaka, 1213, Bangladesh;7. Department of Disease Control, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK;1. Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;2. University of Chinese Academy of Sciences, Beijing 100039, China;3. Center for Environmental Biotechnology, The University of Tennessee, Knoxville, TN 37996, USA;4. Department of Biosystems Engineering and Soil Science, The University of Tennessee, Knoxville, TN 37996, USA |
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| 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 Escherichia 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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| Keywords: | Microbial transport Reversible attachment Filtration theory Groundwater |
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