Optimization of combined flotation and filtration at a large water treatment plant

Abstract: The Rietvlei water treatment plant has recently (1988) been upgraded and redesigned to accommodate dissolved air flotation and filtration (DAFF) in the same process unit. The reason for this drastic change was the eutrophication of the raw water which made conventional sedimentation before filtration impossible due to the high algal content of the water. Rietvlei is the first treatment plant in South Africa that makes permanent use of DAFF at full-scale. After operating for a number of years it was possible to identify areas where the operation of this process could possibly be improved. This study was directed at these areas and it was shown that flocculation conditions in the baffled flocculation channel can be satisfactory predicted with the use of the Bratby reactor and the Argaman/Kaufman flocculation model, flocculation can be significantly improved with the aid of a nonionic polyelectrolyte...M. Ing. (Civil Engineering