A Multi-Disciplinary Laboratory And Field Study In Drinking Water Quality: A Novel Technique For Assessing Suspended Solids Concentrations In The Floc Blanket, Analysis Of Floc Blanket Dynamics, And A Field Study Of Sources Of Waterborne Disease Transmission In The Ethiopian Highlands

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This dissertation contains results of investigations related to: (1) application of floc blankets in vertical-upflow sedimentation tanks for low-cost, gravity driven water treatment plants and (2) sources of waterborne disease transmission in the Ethiopian highlands. Floc blankets are fluidized beds of flocculated, suspended particles that can significantly enhance particle removal in vertical-upflow sedimentation tanks relative to the removals obtained in the absence of floc blankets. An experimental apparatus was built to evaluate floc blanket dynamics and mechanisms underlying floc blanket performance. Blanket dynamics are not well understood, but are important for understanding blanket formation and operational control in full-scale water treatment plants. Sequential image analysis provided suspended solids concentration and floc-water interface height (i.e., floc blanket height) through analysis of transmitted light intensity through a 1.3 cm thick section of a floc blanket. Suspended solids concentrations were calibrated to known kaolinite and aluminum hydroxide concentrations and then turbidity measurements were employed to validate image analysis of solids concentration in the floc blanket, as well as in the floc blanket supernatant. Analysis of consecutive images revealed distinct stages in floc blanket formation: thickening (increasing suspended solids concentration) absent a floc-water interface, thickening with an interface, and steady-state. Preliminary performance data suggest blanket performance is more significantly related to blanket suspended solids concentration than blanket height. Future investigators are recommended to study: inflow and bottom geometry conditions which impact re-suspension of particles, mechanisms of particle removal in the blanket, and the impact of natural organic matter (NOM) on blanket performance, formation, and stability. Bacterial counts and household surveys were performed in a town in the Ethiopian Highlands which experienced an acute watery diarrhea (AWD) outbreak in 2008. A multivariate regression model related to household self-reported incidence of diarrhea indicated that the incidence of diarrhea was related to sanitary disposal of feces from children under five, and locating hand washing stations near to household latrines. Significant risk factors (p-value < 0.05) associated with disease incidence varied by socio-economic status, in part, because water, sanitation and hygiene (WASH) behaviors were linked with socio-economic status. All source and household samples for fecal contamination failed World Health Organization (WHO) water quality standards. Analysis of water quality data and risk factors at the household level revealed that household water contamination was likely related to hand contact with water. Analysis of hand rinsing data (before and after hand washing) revealed a significantly higher reduction in microbial contamination when soap was utilized during hand washing (94% reduction with soap compared to 49% for washing with only water). Analysis of these results suggest that future interventions which focus on increasing the number of people who wash their hands with soap or improving household water quality will reduce waterborne disease incidence.

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Committee Chair

Lion, Leonard William
Lion, Leonard William

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Weber-Shirk, Monroe
Bisogni Jr, James John
Weber-Shirk, Monroe
Barrett, Christopher
Steenhuis, Tammo S
Holst-Warhaft, Gail Lillian

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Civil and Environmental Engineering

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Ph. D., Civil and Environmental Engineering

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Doctor of Philosophy

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dissertation or thesis

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