Microbiological assessment of well water at different durations of storage.

Abstract

Water is the most universally used single necessity of life. To attain a safe water quality to various communities, an understanding of water microbiology and chemistry is therefore imperative. In this study, well water at different storage durations of 0, 2, 4, 6 and 8 weeks were assessed for bacteriological quality using standard microbiological techniques. Black barrel-shaped plastic containers (300 liter capacity) were used for different storage durations. Water samples at the different storage durations were collected from each corresponding containers. Sterile swabs were used to sample the sides and bottom of the storage containers to determine the prevalence of specific bacteria present in the samples. The results obtained showed that 0 week storage had the highest (100.00 CFU mL(-1)) coliform counts while the lowest (28 CFU mL(-1)) was obtained for 8 weeks of storage. Escherichia coli were not found in 4, 6 and 8 weeks old water. 0 and 2 weeks old water contained E. coli and the mean values were 1.80 x 10(4) +/- 0.03 and 1.43 x 10(4) +/- 0.01 CFU mL(-1), respectively (p < 0.05). Salmonella organisms were found in the 0 week old water but absent in the 2, 4, 6 and 8 weeks old water. Shigella count (62.33 x 10(2) +/- 45.30 CFU mL(-1)) was highest in 4 week old water while the lowest (11.0 x 10(3) +/- 1.00 CFU mL(-1)) was found in 6 week old water (p < 0.05). Zero week old water had the lowest significant (p < 0.05) value of 0.35 x 10(4) +/- 0.05 CFU mL(-1) for mesophilic bacteria and the highest value of 50.00 x 10(4) +/- 10.0 CFU mL(-1) was recorded in the 8 weeks old water. Sides and bottom samples were contaminated with coliforms, E. coli, Salmonella and Shigella organisms. It was concluded that the variously stored well water samples were contaminated with bacteria and the values obtained were above the recommended standards by the World Health Organization (WHO).