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Water Transport, Retention, and Survival of Escherichia coli in Unsaturated Porous Media: A Comprehensive Review of Processes, Models, and Factors
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment research group)ORCID iD: 0000-0002-5290-5704
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment research group)
Makerere University, Department of Civil Engineering, Kampala, Uganda.
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment research group)
2015 (English)In: Critical reviews in environmental science and technology, ISSN 1064-3389, E-ISSN 1547-6537, Vol. 45, no 1Article, review/survey (Refereed) Published
Abstract [en]

The vadose zone can function as both a filter and a passage for bacteria. This review evaluates when and why either effect will apply based on available literature. It summarizes theories and experimental research that address the related, underlying bacterial attenuation processes, the applied macro-scale modeling approaches, and the influencing factors - including the cell, soil, solution and system characteristics. Results point to that the relative importance of each removal mechanism depends on the moisture content and the solution ionic strength. The limitations of available modeling approaches are discussed. It remains unclear in which contexts these are reliable for predictions. The temporal first-order kinetic Escherichia coli (E. coli) removal coefficient ranges three orders of magnitude, from 10(-4) to 10(-1)/min. Results suggest that this rate depends on the pore-water velocity. Spatial filtration of E. coli increases with slower flow and higher collector surface heterogeneity. It could be insignificant in the case of heavy and sudden infiltration and subsequent transport in preferential flow paths, induced, for example, by plant roots or cracks in clayey soils. Future research thus needs to address transport as an effect of extreme weather events such as droughts and subsequent floods.

Place, publisher, year, edition, pages
2015. Vol. 45, no 1
Keyword [en]
Unsaturated Attachment, Straining, Survival, Preferential transport, Escherichia coli, Subsurface modeling
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-138609DOI: 10.1080/10643389.2013.828363ISI: 000343312400001Scopus ID: 2-s2.0-84923350845OAI: oai:DiVA.org:kth-138609DiVA: diva2:681584
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Note

QC 20141114

Available from: 2013-12-20 Created: 2013-12-20 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Predicting the transport of Escherichia coli to groundwater
Open this publication in new window or tab >>Predicting the transport of Escherichia coli to groundwater
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Groundwater contamination with pathogens poses a health risk worldwide. Predictive modeling could provide decision support for risk analysis in this context. This study therefore aimed to improve predictive modeling of the transport of Escherichia coli (E. coli) to groundwater. Primarily, it included a review of the state-of-the-art of the underlying process, influencing factors and modeling approaches that relate to E. coli transport in the unsaturated zone. Subsequently, two recently developed models were innovatively applied to the context of microbial contamination. The Active Region Model was evaluated as an alternative to the traditional, uniform flow model (Richard’s equation) to describe bacterial transport in a wastewater treatment facility. It resulted in removal rates that were two orders of magnitude smaller than the traditional approach, more consistently with observations. The study moreover assessed the relevance of a spatial probit model to estimate the probability of groundwater source contamination with thermotolerant coliforms in a case study in Juba, South Sudan. A conventional probit regression model resulted in spatially auto-correlated residuals, pointing to that the spatial model was more accurate. The results of this approach indicated that the local topography and the near presence of areas with informal settlements (Tukul zones) were associated with contamination. Statistical analyses moreover suggested that the depth of cumulative, long-term antecedent rainfall and on-site hygiene were significant risk factors. The findings indicated that the contributing groundwater was contaminated in Juba, and that contamination could be both local and regional in extent. They are relevant for environments with similar climatic, hydrogeological and socioeconomic characteristics, which are common in Sub-Saharan Africa. The results indicated that it is important to consider spatial interactions in this subject area. There is a need for studies that assess the distance within which such interactions can occur, using both mechanistic and statistical methods. Lastly, the results in this study consistently emphasized the importance of flow patterns for E. coli transport. It is thus recommended that future studies evaluate how models of preferential flow and transport can incorporate microbial fate. The multidisciplinary nature of the subject calls for a systems approach and collaboration between disciplines.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. x, 34 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2015:04
National Category
Environmental Engineering
Identifiers
urn:nbn:se:kth:diva-168242 (URN)978-91-7595-618-3 (ISBN)
Public defence
2015-06-15, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20150529

Available from: 2015-05-29 Created: 2015-05-29 Last updated: 2015-05-29Bibliographically approved

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Engström, Emma

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