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Title: Status of Water Quality during the Dry Season in the Addis Ababa Water Supply System
???metadata.dc.contributor.*???: Dr. Mekibib Dawit
Almaz, Shitie
Keywords: Addis Ababa;pollution;water quality;water treatment
Issue Date: Jun-2011
Publisher: aau
Abstract: The water quality and pollution status of the water supply system of the city of Addis Ababa has been studied along three main distribution lines representing Gefersa and Legedadi reservoirs and the Akaki well field starting from raw water until it reaches the end user (tap water). The water quality parameters considered include physical, chemical and bacteriological characteristics. Electrical conductivity, pH, temperature, FCR and turbidity were measured in situ. BOD, COD, TC, FC, Na, K, Ca, Mg, total iron, Mn, NO3 -, PO4-P, Cl-, HCO3 -, CO- 3, SO4 2-, OH- alkalinity and total alkalinity were determined in the laboratory. A total of 69 water samples were collected for laboratory analysis. In each distribution system samples were collected at four sites (raw water, sample immediately after first treatment, selected site along the distribution line and finally from end users tap water). The result displays interesting water quality changes along the distribution line. The reservoir raw water is distinctly different from the groundwater in terms of total ionic concentration. The latter has higher ionic concentration and nitrate content. The raw water of Legedadi shows high phosphate content, 416.93 mg/L, probably associated with high fertilizer usage in its catchment. The very low phosphate content ranged from 0.61 to 11.43 mg/L in the tap and intermediate reservoir sites indicate the effectiveness of the treatment system with coagulation. With regard to bacteriological analysis, the primary data shows that the water is safe for drinking. However, secondary records show occasional traces of in the piped water probably related to the mix of the water with sewerage system in older leaking pipes. The Biological Oxygen Demand and Chemical Oxygen Demand analysis shows that there is some organic pollution. The range of free chlorine residue was 0.08 - 0.91 mg/L and this assessment indicates that the added chlorine is not effective everywhere. This can be seen from the detection of total coliforms in the piped water. The major anion and cation analysis revealed that all the values are within the WHO permissible limit for drinking. However, occasional high total iron may lead in few places to consumer complaints. Calcium and bicarbonate are the main cation and anion, respectively. The three lines studied may not entirely represent the conditions of the Addis Ababa water supply system. It is recommended that more water sampling and analysis is required to have a clear picture and trace the source of specific pollution.
Description: A Thesis submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Environmental Science
Appears in Collections:Thesis - Environmental Science

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