Effects of Sunlight Exposure on the Quality Parameters of Bottled Water

This study was conducted to determine the physicochemical, heavy metal and microbiological effect of sunlight exposure on bottled water quality. Nine brands of bottled water commonly produced and sold in Benin City were exposed to sunlight for 0 day, 14 days and 28 days and evaluated for physicochemical parameters (pH, EC, TDS, alkalinity, hardness, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^- ), heavy metals levels (Pb, Cd, Zn, As) and microbial content using standard methods. Results obtained showed that 96.30% of the pH values were below the WHO (6.5-8.5), SON (6.5-8.5) and NIS (7.5) standards, a gradual decline in the values was also observed with increasing sunlight exposure. Other physicochemical parameters were within the established standards with steady increments in the values with increasing sunlight exposure, except for alkalinity which declined consistently due to increase in the acidity levels of the water samples. There was a general increase in the Zn concentration for all bottled water brands from 0 day to 28 days, except for brand C which remained the same, while Pb, Cd, As level were not detected. Interestingly, a gradual decrease of the microbial population (total coliform) of the bottled water with increasing exposure to sunlight was observed. In all, the varying exposure to sunlight did not result in statistical significant changes (P< 0.05) in the water quality.

Keywords
Bottled water; sunlight exposure; physicochemical parameters; heavy metals; microbial content.