Operating diagnostics on a flocculator-settling tank using fluent CFD software

FLUENT CFD software was used to form an understanding of a periodic dysfunc tion at a drinking water production plant at a site in North Africa. The st ructure involved is a circular, 27-metre diameter, flocculator-settling tan k, supplied with surface water taken from the nearby river. The following d ysfunction was observed on the structure in question. In summer, during the hottest time of the day, a cloud of flocs would sometimes rise to the surf ace, appearing in the centre of the settling zone. The cloud then progresse d slowly to the outer zone of the tank, where a proportion of the total sus pended solids (TSS) would overflow, impairing the quality of the treated wa ter. The CFD simulations enabled us to understand the precise mechanisms in operation when the phenomenon is observed. (C) 1999 IAWQ Published by Else vier Science Ltd. All rights reserved.