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Prevalence of microbiological contaminants in groundwater sources and risk factor assessment in Juba, South Sudan
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment)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)
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment)ORCID iD: 0000-0002-1640-8946
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. (Environmental Management and Assessment)
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2015 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 515-516, 181-187 p.Article in journal (Refereed) Published
Abstract [en]

In low-income regions, drinking water is often derived from groundwater sources, which might spread diarrheal disease if they are microbiologically polluted. This study aimed to investigate the occurrence of fecal contamination in 147 improved groundwater sources in Juba, South Sudan and to assess potential contributing risk factors, based on bivariate statistical analysis. Thermotolerant coliforms (TTCs) were detected in 66% of the investigated sources, including 95 boreholes, breaching the health-based recommendations for drinking water. A significant association (p<. 0.05) was determined between the presence of TTCs and the depth of cumulative, long-term prior precipitation (both within the previous five days and within the past month). No such link was found to short-term rainfall, the presence of latrines or damages in the borehole apron. However, the risk factor analysis further suggested, to a lesser degree, that the local topography and on-site hygiene were additionally significant. In summary, the analysis indicated that an important contamination mechanism was fecal pollution of the contributing groundwater, which was unlikely due to the presence of latrines; instead, infiltration from contaminated surface water was more probable. The reduction in fecal sources in the environment in Juba is thus recommended, for example, through constructing latrines or designating protection areas near water sources. The study results contribute to the understanding of microbiological contamination of groundwater sources in areas with low incomes and high population densities, tropical climates and weathered basement complex environments, which are common in urban sub-Saharan Africa.

Place, publisher, year, edition, pages
2015. Vol. 515-516, 181-187 p.
National Category
Environmental Sciences
Research subject
Land and Water Resources Engineering
Identifiers
URN: urn:nbn:se:kth:diva-159751DOI: 10.1016/j.scitotenv.2015.02.023ISI: 000352040700018Scopus ID: 2-s2.0-84923383854OAI: oai:DiVA.org:kth-159751DiVA: diva2:787302
Note

QC 20150519

Available from: 2015-02-09 Created: 2015-02-09 Last updated: 2017-12-04Bibliographically 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, EmmaMörtberg, Ulla

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