Microbiological criteria of tap water passed through some storage water tanks in Greater Cairo

Shortage in drinking water supply led to an increase of pumping water to storage tanks and its redistribution to the consumers. The water quality may be changed according to the storage condition and to the deficiency in cleaning of those tanks. Water samples were taken from the tanks of Helwan and El-Giza governorates (Cairo, Egypt) and examined to evaluate microbial water quality. The results revealed that all water samples were free from total coliforms, faecal streptococci, sulphite reducing bacteria (clostridia), salmonellae groups and total vibrios. The total bacterial counts at 37°C and 22°C were 32 to 185 and 11 to 135 cfu*100ml-1, respectively. The total yeast and fungi counts were 9 to 66 and 4 to 35 cfu*100ml-1, respectively. Total counts of staphylococci (from 2 to 17 cfu*100ml-1), Pseudomonas aeruginosa (from 33 to 58 cfu*100ml-1), and coliphage (from 7 to 13 cfu*100ml-1) were also estimated. The free-living amoebae were detected in 75% of the examined storage water tank samples. According to the Egyptian standard for drinking water, most of the examined water samples were not acceptable for human consumption