Quantification of Bacteria in Domestic Water Storage Tanks in Sharjah

Abstract

Maintaining the microbiological quality of water is an important means of preventing water-bornediseases. The aim of the present study was to use the Membrane Filter (MF) method to examine the level of coliforms (Escherichia coli)and total bacteria in water storage tanks fitted in different homes in Sharjah. The MF method can determine the presence or absence of bacteria within only 24 hours. A volume of 100ml of water sample is filtered through bacterial retaining membrane; the membrane is then transferred to a selective media and incubated for 24h at 37ᵒC to enable the growth of the bacteria. On the growing plates, Total Bacterial Count (TBC) shows as yellow colonies, Total coliforms (TC)shows as dark red colonies and E. colishows as dark blue colonies. Eleven houses were sampled for along a period of six weeks. Samples were collected from two storage tank levels (ground level and roof top level) located in each house. The results showed that, although none of the samples contained E. coli, they did contain other coliforms. The absence of E.coli indicate no fecal contamination by animal and/or human, on the other hand, other Coliform bacteria were present in water which are usually introduced by the environment such as Klebsiella, Enterobacter spp., and Serratia. These isolates pose a health risk if they reach the human system. More than half of the samples collected (72.7%) showed a high TBC (>10CFU/100ml), which suggests further investigation is needed to examine the sources of contamination to the storage tanks. The bacterial contaminants found in the storage tanks usually come from the environment which may indicate the presence of other contaminants like chemical contaminants that are also found in the environment and entered via the same route to the storage tanks. The results of this study suggest the adoption of a cleaning system for the water tank at least twice a year to prevent accumulation of contaminants. In addition, the results suggest that chemical contaminants might be present in the water, therefore, chemical analysis is recommended.