Graduation Year

2023

Document Type

Thesis

Degree

M.S.E.V.

Degree Name

MS in Environmental Engr. (M.S.E.V.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Katherine Alfredo, Ph.D.

Committee Member

James Mihelcic, Ph.D.

Committee Member

Maya Trotz, Ph.D.

Keywords

disinfectant residual, L. pneumophila, opportunistic premise plumbing pathogens, Small Island Developing States, water scarcity

Abstract

There have been many initiatives to combat the global phenomenon of water scarcity. Potable water storage tanks have become widely known among water insecure countries and communities to provide adequate water quantity and quality for consumer use. Despite ubiquitous use in many low- and middle-income communities (LMIC), knowledge of microbial activity inside potable water storage tanks is limited. Barbados is a Small Island Developing State (SIDS), labeled as a high income country, and also water scarce. The Barbados Water Authority (BWA) has adapted potable water storage tanks for hundreds of residents as a solution to water quantity and water quality issues. In the summer of 2022, a collection of eight old (>1 year) and new (<1 year) potable water storage tanks across Barbados were sampled throughout the day for chemical compliance of nitrate and total chlorine residual, as well as microbial presence and activity that includes total coliforms, Escherichia coli (E. coli), and Legionella pneumophila (L. pneumophila). All tanks sampled had nitrate concentrations below regulated thresholds. Chlorine residuals, however, were often too low in tanks with concentrations below the WHO drinking water guideline of 0.2 mg/L minimum. Many tanks tested positive for total coliforms (5) and E. coli (3). There was no statistical significance regarding the time at which samples were collected for total coliforms or E. coli, but there was a statistical significance of coliform contamination based on tank age, as total coliform was more prevalent in new tank whereas E. coli was more prevalent in old tanks. Conditions of the water inside the tanks were optimal for L. pneumophila to grow as temperatures for all sampled water were within the bacteria’s growth range (25-45°C) and exhibited insufficient chlorine residuals. However, despite these optimal conditions, three of the eight tanks tested positive for L. pneumophila suggesting growth unique within each tank. It is recommended that more sampling take place to include old and new tanks to evaluate key drivers for microbial growth within these tanks. Once this is understood, development of operational and maintenance plans to mitigate microbial growth are possible for both the BWA and tank owners.

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