Abstract
Mpira Balaka, a full scale rural water supply project was constructed in Ntcheu, Malawi, in 1988 utilising Slow Sand Filtration (SSF) as the main treatment process and roughing filtration as the pretreatment method,following the promo- tion of this technology by various international institutions. During the rainy seasons, the treatment plant for Mpira Balaka failed to cope with the high raw water turbidity, resulting into very short filter run times and hence also to unavoidable distribution Of very turbid water to the rural communi- ties as a result Of by-passing the filters. Of the fifty or so existing rural projects in Malawi, Mpira-Balaka, the biggest rural project until then, was beset with unforeseen design, treatment and opera- tional problems. In an attempt to rectify the situation, a number of consultants Were called to advise the Water Department, eventually resulting in the modifica- tion Of the existing roughing filters to Downflow type. Since the suggestions put forward by the consultants and the manner in which the modifications were implemented was rather adhoc in nature, this paper Scien- tifically establishes the efficacy Of the modifications made to the roughing filters, and evaluates the treatment performance prior to, during and after the modifica- tion of the roughing filters. The study was conducted at the University of Dar es Salaam using data collected in Malawi. Notable improvements in some water quality parameters have been observed. The mean monthly turbidity removals through the system prior to, during and after the modifications were 37%, 54% Critical Evaluation of Effects of Changes Made to Roughing Yilters and 88%, respectively. During the same period the mean monthly faecal colifonn percentage removals observed were 77.8%, 80% and 90%, respectively. Mean SSF run times increased from 23 dCiys prior to the modification to 58 days after. The observed improvements in the overall plant performance are directly related to the modification in the design and construction of the Downflow Rough- ing Filters.
Recommended Citation
Zulu, C. (1993). CRITICAL EVALUATION OF THE EFFECTS OF CHANGES MADE TO ROUGHING FILTERS OF MPIRA-BALAKA PLANT ON ITS TREATMENT AND OPERATIONAL PERFORMANCE. Tanzania Journal of Engineering and Technology (TJET), 17(2), 21-46. https://doi.org/https://doi.org/10.52339/tjet.v17i2.151
Publisher Name
University of Dar es Salaam