A laboratory evaluation of the treatment performance of annular horizontal flow roughing filters

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University of Dar es Salaam
The research with the Annular Horizontal-Flow Roughing Filter (HRF) design was meant to establish its potential and advantages as an alternative pretreatment prior to Slow Sand Filtration or as a sole filtration unit in rural water schemes in practice when compared with the conventional rectangular HRF design. The treatment performance was evaluated with respect to physical parameters such as the turbidity, filterability, settle ability, suspended solids, legibility, apparent colour and pH. The preliminary results of the laboratory tests conducted with filtration rates ranging from 0.5 to 2.0 m/h and gravel of 3 different fractions (4-32, 8-32, 16-62 mm) revealed that at filtration rate of 0.5 m/h, the maximum removal efficiencies of the filter with respect to the turbidity, apparent colour, and suspended solids are 76 %, 50 % and 50 %, respectively. The results agree favourably with the performance of the conventional rectangular HRF units. The treatment performance of the proposed annular shaped HRF design was evaluated. Comparison of the filtrate quality with the conventional rectangular HRF, WHO guidelines far drinking water and Tanzanian drinking water standards shows that the filtrate quality of the annular shaped HRF is within the acceptable limits and therefore, could be adopted as pretreatment prior to slow sand filter. However, detailed chemical, bacteriological and field tests are required in order to fully establish the potential and advantages of the design in practice.
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Filters and filtration, Water, Filtration
Mosuro, A. M (1992) A laboratory evaluation of the treatment performance of annular horizontal flow roughing filters,Masters dissertation, University of Dar es Salaam. Available at ( )