A monthly evaluation of microbiological and chemical quality of bottled drinking water

Abstract

Use of bottled water has flourished in Sri Lanka, owing to its high demand, however, the quality of commercially available bottled drinking water is questionable. The objective of the current study was to assess the monthly variation of microbiological and chemical quality of bottled water. Three brands were selected, twenty-four bottles of each brand were collected for analysis. Microbiological and chemical analysis were carried out monthly. Though the shelf life of bottled drinking water is one year, the experiment was terminated in eight months as bacterial counts showed a steady decline with time as follows. The results indicated that Total Coliform [TC], Fecal Coliform [FC] and Heterotrophic Plate Count [HPC] bacteria decreased throughout the shelf life. There were significant differences in TC (P&lt;0.05) and FC (P&lt;0.01) between microorganisms initially present and after eight months of storage. Even though SLSI permitted levels for presumptive TC is less than zero cfu per 100ml, the average count of TC was 139 cfu per 100 ml at the end of the first month. According to national and international standards, the FC count should be zero per 100 ml for drinking water. However, at the first month some bottled water samples exceeded this limit for presumptive FC, with an average count of 32.5 cfu per 100 ml. For HPC bacteria, only one brand exceeded the WHO guidelines (50 cfu/ml). No algal species were detected. Fungal colonies showed a reduction in number over an eight-month duration. <em>Penicillium </em>sp. and <em>Aspergillus </em>sp. were dominant. Chemical parameters were within the permitted levels, except hardness in water samples. The result of this study reveals that the bottled water industry needs to be monitored closely and continuously by relevant authorities, intending to provide safe bottled water to the public.