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Abstract:
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An investigation of the use of Upflow Gravel Bed Flocculator (UGBF) to flocculate colloidal particles caused by Kenya's laterite soil, i.e. red coffee soil, has been carried out. The theory part of the report has dealt with the basic theories of coagulation and flocculation. Basic literature on the subject has also been presented. Experiments that have been conducted have tried to establish whether UGBF could be an econimically viable alternative to the conventional goagulation- flocculation units. The efficiency of coagulaton-flocculation has been assessed bydetermining effluent turbidity, floc quality and flocsettlement properties. It has been established that graded media is more efficient in UGBF than uniform media. It has further been established that graded media is especially good media for use in the UGBF with uniform cross-section. An UGBF run of 81/2 hours was got when the flow through the cylindrical UGBF was 11,5 m/h. The level of turbidity varied between 126 and 400 NTU. For the case of tapering UGBF, it has been established that to get runs of adequate length, it is advisable to use media of sizes 6 - 13 mm throughout the bed. The flow should then be maintained between 9,0 and 14,4 m/h. UGBF could find a lot of use for rural water supply schemes. For these water supplies economy is of the utmost importance. UGBF is a relatively cheap unit to construct and operate. Its operation and maintenance costs are also quite low compared to other conventional units. This unit requires only a head of 1,5 - 2 m. It would find application in any area where the raw water has some head. Topography of the area could also be used in order to give the extra head required for UGBF. /Kir09 |