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

James Mihelcic, Ph.D.

Co-Major Professor

Katherine Alfredo, Ph.D.

Committee Member

Mauricio Arias, Ph.D.

Keywords

3-AFC, Disinfection, Drinking Water, Sustainable Development Goals, Taste Perceptions

Abstract

More than two billion people globally still lack access to safely managed drinking water (WHO & UNICEF, 2021). Although gains in access to water service over the past two decades have been large, universal access to safe and affordable drinking water (SDG 6, target 6.1) is not on track to be achieved. In Panama, safely managed drinking water access has not been measured. However, the data on basic water access illustrates the large disparities between rural and urban areas of Panama. While 98% of urban Panamanian households have basic access to water, only 86% of rural Panamanian households, and 54% of households in the Comarca Ngäbe-Buglé have basic access (WHO & UNICEF, 2021).

Improving from basic water access to safely managed water access usually necessitates consistent water treatment. In the Comarca Ngäbe-Buglé, chlorination is the most popular form of water treatment (24% of households) but is still not well adopted (World Bank Group, 2018). This study examines and compares free chlorine taste and acceptability thresholds of rural Indigenous Ngäbe Panamanians and rural Latino Panamanians to study if taste aversion may be a limiting factor in chlorination of community systems in rural Panama. The 3-Alternative Forced Choice Test (3-AFC) methodology was used to determine best-estimate individual and group taste and acceptability thresholds. 146 participants from nine different communities participated fully in the taste experiment and subsequent questions about the taste of the water they were sampling between May 27, 2021 and September 18, 2021.

Study results show that mean and median thresholds for the Indigenous Ngäbe study participants were lower than Latino participants, but statistically insignificant. Taste thresholds were 0.87 mg/L Cl2 for Indigenous Ngäbe participants (n = 82) and were 1.64 mg/L Cl2 for Latino participants (n = 64). Full data median taste thresholds measured 1.01 mg/L Cl2, and median acceptability thresholds were 3.45 mg/L Cl2. Indigenous Ngäbe participants rejected chlorinated samples at more than three times the rate of Latino participants. At concentrations higher than 0.6 mg/L Cl2, Indigenous Ngäbe participants significantly rejected samples as a function of free chlorination level.

Linear regression results indicate that smokers had significantly higher taste thresholds than non-smokers. Age, sex, use of chlorine in the household, and difficulty of access were not significantly statistically linked to taste thresholds. A multivariate logistical model shows that Indigenous Ngäbe participants were significantly more likely to have taste thresholds less than 1.0 mg/L Cl2 than Latino participants.

The results of this research illustrate opportunities to support rural communities in Panama in managing the treatment of their own water supplies by identifying chlorine taste threshold concentrations for two sub-national groups. Knowledge of chlorine taste and acceptability thresholds and how they vary within Panama can inform officials how to best recommend safe and acceptable chlorine dosage guidelines.

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