Turbine flocculators

Propeller or turbine blade flocculators are difficult to assess from a theoretical standpoint as they vary greatly in form and efficiency. An example of successful taper flocculation using turbine agitators is described by Bernhardt and Schell, for the formation of ferric hydroxide floes for phosphorus removal of the water supplying the Wahnbachtal reservoir. The practical approach to such propeUer/turbine flocculators is to make torque... 

Rotary vertical shaft turbine units as shown in Figure 10 and other rotary or reciprocating equipment are other examples. Tapered flocculation may be obtained by varying reel or paddle size on horizontal common shaft units or by varying speed on units with separate shafts and drives. In applications other than coagulation with alum or iron salts, flocculation parameters may be quite different. Lime precipitates are granular and benefit little from prolonged flocculation. 

Equipment typically consists of concentric circular compartments for mixing, flocculation and settling. Velocity gradients in the mixing and flocculation compartments are developed by turbine pumping within the unit and by velocity dissipation at baffles. For ideal flexibihty it is desirable to independently control the intensity of mixing and sludge scraper drive speed in the different compartments. 

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