الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Now with modern civilization and high buildings era, roof tanks are used to store drinking water in high percentage of such buildings for augmentation in demand hours. In a previous study acarried out in Alexandria in 1985, indicator bacteria have been demonstrated in 85 of tanks water. Hence the idea of investigating such water for presence of sane pathogenic bacteria. This study was carried out on a total of 330 water samples collected from tanks of different~type5 (barrel, steel plates, cement and fiber glass) . Water samples were also collected from the first floors -supplied directly from the main pipes- of thirty of the buildings using the abcrve tanks. All samples were examined for their pH, residual chlorine and turbidity, as well as Ps. aeruginosa and Staph. ~~ MPN which was determined by the multiple tube method and Salmonella and Shigella isolation using the qualitative metRod. The results of this study revealed the following: Out of the 330 water samples collected from tanks, 88 (26.6670) were ~ositive for Ps. aeruginos8 by the multiple tube method, detailed ~ [22 (25) fr~n barrel tanks, 25 (28.40) from steel plate, 33 (37.570) from cement and 8 (9.09) from fiber glass). Also Ps. aeruginosa was isolated fra.1\ 107 (32.42’70) samples by the qualitative method used for the isolati.on of Salmonella and Shigella, detailed as (24 (22.42’70) from barrel, 32 (29.90’70) from steel plate, (40 (37.38) from cement and 11 (l0.28) from fiber glass). Staph. aureus was isolated from 30 (9.09’70) samples, detailed as (8 (26.66’70) fro~ barrel, 11 (36.66’70) from steel plate, la (33.3310) from cement and 1 (3.3310) from fiber glass).. E.. typhimurium was isolated from 2 (0.6010) samples (from cement tanks). No~e of the studied samples showed Shigella. Out of the 30 water samples that were collected from the main water supply, only 2 samples were p03itive for r~. aeru~inosa and none showed Staph. aureus. Moat of the barrel, steel plate and cement tanks were uncovered while most of fiber glass tanks were covered. The highest MPN reached by Ps. aeru~inosa was >9oo/lOOml and this was found in a steel plate tank while the highest MPN of Ps. aeruginosa in fiber glass tanks was only 2-lo/1ooml. Regarding Staph. aureus, the highest MPN was 2l-30YloOml and this was found ,in both steel plate and cement tanks. Only one sample”from a fiber glas~ tank was positive for Staph. aureus and showed a MPN of 2-lo/looml. ~. tvphtmurium was isolated from two cement tanks that were uncovered and there was birds in their vicinities. ) The studied water samples showed a pH ranging between 7.0&7.8 and a turbidity ranging between < 5& >5 T. U. The residual chlorine of water from tanks ranged between <°.1& >1.0 mg’L and that of the main water supply ranged between 0. 1& > 1. ° mg’L. In conclusion, it was expected that water stored in cement and steel plate tanks w~Jld be of a better quality than that stored in barrel tanks. This study showed that there was no difference between these three types and the best type of the studied tanks was the fiber glass concerning bacterial contamination. Also, this study shoNed that birds play a significant role in contamination of tank’s water and absence of cover had a bad effect on the quality of such water.