Browsing by Author "Zulu, Christopher Kaminga"

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    Critical examination of the current design, treatment and operational performance of the downflow roughing filters of Mpira Balaka plant.
    (University of Dar es Salaam, 1993) Zulu, Christopher Kaminga
    Mpira Balaka, a full scale rural water supply project was constructed in Ntcheu in 1988 utilising slow sand filtration as the main treatment process and roughing filtration as the pretreatment method, following the promotion of this technology. During the first rainy season, and indeed all the rainy seasons after this, the treatment plant failed to cope with the raw water quality, resulting into unavoidable distribution of very turbid water to the rural communities. Of the fifty or so existing rural projects in Malawi, Mpira Balaka, the biggest rural project so far, was beset with unforeseen problems. In an attempt to rectify the situation in time before the rural communities who dig the pipeline trenches on self-help basis get demotivated, a number of consultants were called to render their services, eventually resulting in the modification of the roughing filters. Noting that the suggestions put forward and the manner in which the modifications were implemented was rather adhoc in nature, this research tries to determine the efficacy of the modifications made to the roughing filters, evaluate treatment performance prior to during and after the modification of the roughing filter. This study was conducted at the University of Dar es Salaam using data collected from independent laboratories. The data was grouped in three periods in relation to state of the roughing filters: prior to, during and after modification of the roughing filters. The modifications of the roughing filters effectively commenced and finished in April 1991 and March 1992, respectively. The periods before April 1991 and after March 1992, are considered prior to, and after the modification of the roughing filters, respectively. On assessing the available treatment and operational data, this study has shown there are notable improvements in the removal of some parameters. The mean monthly turbidity removals from between the raw water and the slow sand filtrate prior to, during and after the modifications were 37%, 54 % and 88%, respectively. Prior to, during and after the modification of the roughing filters, the mean coliform percentage removals were 77.8%, 80% and 90%, respectively. Slow sand filter run times increased from 22 days prior to the modification to 58 days after. The observed improvements in the overall plant performance were directly related to the design and construction of the DRF.