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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/3506

Title: Optimization of the operational cost of water supply to the city of Accra
Authors: Lokko, Frederick Christian
Issue Date: 12-Sep-1988
Series/Report no.: 1939;
Abstract: The City of Accra is supplied with potable water from two sources; namely, the Kpong and the Weija Works. Raw water quality at Weija is poor. It has high turbidity and suspended solids content; and moreover, algal growth occurs in the impounded reservoir. For these reasons, full conventional treatment is undertaken at Weija to barely bring the quality of the product water within the WHO Quality Standards. At Kpong however, raw water quality is high for most of the year and therefore clarification by use of alum is not, necessary, and is hence not generally practised. Water treatment cost is therefore significantly lower at Kpong than at Weija since the cost of imported alum is largely saved at the former plant. On the other hand, transmission of treated water from Weija to Accra is by gravity over a relatively shorter distance, while from Kpong, potable water is pumped a relatively longer distance, to the City. Transmission cost of water from Weija is thus much lower than from Kpong. In order, to minimise the overall cost of water supply to the City of Accra, a Direct Search optimization technique is used in this work, to obtain optimal quantities of abstraction from each of the Kpong and Weija Works. Under the Accra-Tema Water Supply and Sewerage Master Plan, parallel pipelines will be laid from Kpong to Tema and Tema to Accra. Parallel raw water rising mains are also planned. The effect of a parallel transmission main from Kpong to Tema on the operational cost of water supply to Accra and also on the optimal quantities of abstraction is determined. It is found that for the existing system characteristics of the Accra-Tema Water Supply System, the cost of Water Supply to Accra from Weija is lower than from Kpong. It is also found that the introduction of a parallel pipeline from Kpong to Tema reduces the transmission cost of potable water from Kpong thus increasing the optimal percentage of abstraction from that source. Population and water demand forecasts which form the basis of the Accra-Tema Water Supply and Sewerage Development Master Plan of 1981, are reviewed in the light of more recent (1984) population census data. It is found that the population and therefore the demand projections used in the Master Plan are high. The proposed implementation schedule of works is therefore retarded such that the supply capacities of the Kpong and Weija plants correspond with the revised demands at all times during the planning period.
Description: A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Sanitary Engineering, 1988
URI: http://hdl.handle.net/123456789/3506
Appears in Collections:College of Engineering

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