| Summary: | Chemical treatment is the most often method used in water treatment in the Czech republic. It is based on dosage of destabilisation reagent into raw water, formation of separable aggregates and their separation by sand filtration. Waterworks optimalisation is predominantly carried out by change of the chemical parameters, typically by change of destabilisation reagent dose. Physical parameters in water treatment like the magnitude of the velocity gradient and period of its duration are undervalued commonly, although they have crucial effect on quality of the aggregates. Character of the aggregates (size, density, compactness) influence their separability. This study aims at evaluation of influence of the magnitude of the velocity gradient on quality of suspension formed. Infuence of stirring intensity was performed on the pilot plant situated in the Želivka waterworks, which is fed from Švihov reservoir. The pilot plant worked at two modes: 1) slow stirring by perforated baffles and 2) fast stirring by fluidised layer of granular material. Fast stirring was either aggregational (served only as stirring element), or separational (separation of aggregates proceed already in the fluidised layer) Infuence of the magnitude of velocity gradient was evaluated by aggregation test. Seperation effectivity...
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