Graduation Year

2022

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Jeffrey Cunningham, Ph.D.

Co-Major Professor

James Mihelcic, Ph.D.

Committee Member

Sarina Ergas, Ph.D.

Keywords

Biofilm, Diarrheal Diseases, Disinfection, Pathogen, Safe Water System, Sûr’ Eau

Abstract

As of 2020, diarrheal diseases were the leading cause of death in Madagascar. A major cause of diarrheal illness is contaminated water, and one crucial aspect of preventing contaminated water is safe household storage. Bacterial regrowth between point-of-collection and household storage has been well established in literature. A frequently implicated source of regrowth is the storage container’s biofilm, which is a community of varying bacteria enclosed in a “slimy” extracellular polymeric substance that forms on surfaces in wet environments and anchors bacteria to those surfaces. The overall goal of this thesis was to quantify and control bacterial regrowth in household storage containers in eastern coastal Madagascar. Previous literature has looked at biofilm cleaning methods in laboratory settings, or in field settings with methods that were not necessarily locally available or affordable. This thesis research is novel in that it seeks to fill in a knowledge gap around locally available and economically viable cleaning methods for reducing biofilms in real-world, uncleaned jerricans.

The major research objectives were to (1) quantify regrowth between source and storage, (2) determine if there is a correlation between bacterial regrowth and water source and/or between bacterial regrowth and type of household storage container, (3) test the hypothesis that biofilms are a source of regrowth in jerricans (HDPE 20 L vessels used to collect and transport water), and (4) test the efficacy of locally available cleaning methods on jerrican biofilms in Toamasina, Madagascar.

Water samples were collected from collection sources and storage containers at 10 households. Water sources included shallow self-supply groundwater pumps, called paompy tany, and tap water provided by the national utility service, JIRAMA. Household storage containers included five open and five closed vessels. At each household, samples were taken twice over a two-week period from both the point of collection and storage containers in sterilized Whirl-paks containing sodium thiosulfate. Samples were immediately taken to the laboratory of USF’s local partner (Ranontsika) and were tested for Enterococcus, total coliforms, Escherichia coli, Pseudomonas aeruginosa, and Clostridium perfringens via standard membrane filtration procedures to quantify bacterial regrowth. Following this two-week period, the jerricans showing contamination were collected from households and tested in the laboratory to determine if biofilms on the jerricans were sources of contamination. Finally, a total of 12 jerricans were collected to test the efficacy of locally available and financially viable cleaning methods. The 12 jerricans were split into four groups, each with three jerricans of varying dirt levels based on visual inspection. The four cleaning methods were soapy water, Manadio Rano (sodium hypochlorite), baking soda and vinegar, and no cleaning (negative control group).

All households showed evidence of bacterial water quality degradation between source and storage on at least one sampling occasion, which is consistent with literature and indicates bacterial regrowth is a significant phenomenon in Toamasina, Madagascar. Of the four jerricans used to test for biofilms, all showed at least one of the fecal bacteria, indicating that jerrican biofilms are a source of regrowth in the Toamasina community. Of the cleaning methods, Manadio Rano proved to be the most effective, with an average removal rate of 90% for Enterococcus and 76% for total coliforms. Manadio Rano was also the most affordable cleaning method, costing about 420 Malagasy ariary or 0.10 US dollars on a per-cleaning basis. For four of the five fecal indicators measured, there were no statistically significant differences in bacterial regrowth between storage container type (open or closed). This differs from previous literature, which had shown that closed storage containers were better than open containers at preventing bacterial regrowth. This difference in findings was likely in part due to the poor quality of household jerricans sampled in the community, which were visibly dirty and confirmed for biofilms. This was an important finding indicating that closed containers may only be safer than open storage containers if they are free of biofilms.

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