الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Raw water delivered to the Alexandria water treatment utilities via the drinking water canal has been characterised by high turbidity, high algal count and high bacteriological content. The bad quality of the raw water dictates the use of full scale coagulation, sedimentation, filtration and disinfection treatment plants in all water treatment utilities covering different sections of the city. The Alexandira General Water Authority has been using sludge blanket clarifiers designed and constructed by the french company, Degremont, for the last 20 years. In these clarifiers, upwards through a blanket. Every few water is circulated intermittently layer of sludge called the sludge minutes, a pulse of water is introduced in the clarifier. Therefore the sludge blanket will be in a homogeneous suspension. Some engineers in the company have observed that water did not suffer any impairment in’quality by omitting the pulse mode of the clarifiec, and operators in the Alexandria General Water Authority tend to omit the pulse mode to get a better yield of water. However, from the theoretical point of view, a few minutes of continuous upward flow will result in the formation of solid mass of compact sludge through which water will have made channels. Therfore, under continuous flow conditions, there will be no longer any effective contact between the particles in water traversing upwards in the clarifier and the sludge and the treated water quality will deteriorate. To verify this assumption, two of the operating pulsators in El-Manshia El-Gidida water treatment plant were investigated. Both received raw water from the same inlet. The pulse mode was operated in one of them and was omitted in the other. Water treated by the pulsators were subsequently treated by rapid sand filtration, one filter being connected to the pulsator, The other to the clarifier operating while omitting the pulse mode. Samples were collected from raw water, at the outlet of the pulsator, at the outlet of the pulsator operating without the pulse mode, at the outlet of the filters. These samples were analysed for turbidity, fixed suspended solids, volatile suspended solids, most probable number, plate count, algal count and residual aluminum. Results of the present investigation indicated that the sludge blanket clarifier whether acting with or without the pulse mode was effective in reducing all the parameters tested. However, the pulsator operating with the pulse mode was more efficient. The pulsator operating without the pulse mode eliminated 46 of raw water turbidity, 28 of raw water fixed suspended solids, 44 of raw water volatile suspended solids, 50 of raw water most probable number, 26 of raw water plate count, 47 of raw water algal count.