... the vertical flow velocity of liquid (both up and down) in the device will decrease as the area is increased and vice versa. In the upper part of the tank net downward motion of solids is reduced, but in the lower section it is increased - relative to a freely settling particle. What area of thickener will ensure a clarified overflow and how can it be reduced (to save space)? Feed Conditioning The surface properties of colloids may be exploited to assist separation, by adjusting conditions so that particle-particle interactions are net attractive. Many particles carry electrostatic charge in aqueous media in general the effects of this may be: 1. Suppressed/reduced by addition of electrolyte 2. Eliminated/exploited by adjustment of pH (or pX, of some other surface reactive ion X). 3. Overwhelmed by addition of polymers/polyelectrolytes. (usually termed flocculants) The size density and strength of the aggregate particles which form are strongly dependent on the conditioning process. For it ...

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