The biological and chemical water quality of retail bottled water brands: a case of Dodoma, Tanzania

Abstract

Purpose Ensuring high water quality is crucial for safeguarding public health, as contaminated water can pose significant risks to consumers’ well-being. This study aims to evaluate the microbiological and chemical quality of bottled water brands commonly consumed in Dodoma, Tanzania. Design/methodology/approach A total of 36 samples from 12 brands were collected between January and March 2023 and analyzed for microbiological and general water quality parameters. Findings Microbial analysis found that 42% of brands tested positive for coliform bacteria, while opportunistic pathogens Aeromonas hydrophila and Pseudomonas aeruginosa were detected in 25% and 17% of samples, respectively. For chemical composition, 42% of brands exceeded the World Health Organization guideline value of 1.5 mg/L for fluoride. However, no other parameters exceeded national drinking water standards. Statistical analysis revealed significantly higher measured fluoride levels compared to values declared on product labels (paired t-test, p = 0.003). A moderate positive correlation between fluoride and conductivity (r = 0.52, p = 0.045) indicated possible geological influences on water chemistry. Research limitations/implications To enhance the study’s comprehensiveness, exploring temporal and spatial variations among water brands, including samples from typically clean environments such as supermarkets, could have been beneficial in identifying underlying factors. Additionally, investigating the entire manufacturing process, from production to end-user, could have provided insights into unforeseen deviations in quality. Furthermore, the use of pour plating techniques at 37°C for microbial analysis, while suitable for resource-limited settings, may not have fully captured coliform diversity compared to membrane filtration and differential temperature incubation as per standard methods. This could partly explain the detection of heterotrophs without higher coliform counts in some samples. Practical implications This study provides baseline data on the bacteriological and inorganic chemical quality of bottled water in Dodoma. Detectable microbial contaminants and significant exceedances of fluoride guidelines in some products raise public health concerns. Originality/value While existing studies focus on bottled water quality at production facilities, this research highlights the overlooked risks at retail points, where consumers are directly affected.