Design Methods for Continuous Settling

These processes can be described most suxply by the Canq)-Hazen ideal conthraous sedimentation tank model iiich equates the residence times derived from the vertical settling motion of the particle and the horizontal plug flow movement brought about by the drag of the liquid. Thus for a residence time t the vertical equation is  

Since =/(x) the separation efficiencies can be estimated for a range of particle size 

Continuous Settling Dilute Systems. When apphed to continuous sedimentation the long tube test is used to model the settling of particles in an elemental vertical volume of liquid moving throu the length of the clarifier. The corresponding overflow rate Vc, of a continuous ideal basin is given by H/ta, where H is the sanq)le point depth. 

Since an overflow system is being designed the corrected concentrations must be averaged over the number of sample points above and including tbe one in question. For exanq)le, if the corrected concentrations measured at sarcple points 1, 2, 3, 4, and 5 (sample point 1 being uppermost) were c l, c 2, c 3, c 4 and c j the average concentrations at those points would be as follows  

Short Tube Test. If the separation is governed simply by overflow rate, i.e. by the settling rate of the particles, a sinqilified procedure using a short tube is enq)loyed, and this is especially suitable for classification and degritting applications. This test uses a plain transparent cylinder about 50 mm diameter and 1 m long with each end closed by a 

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Almost all the design methods for continuous gravity thickener in the zone settling region are based on the following equation (Coe and Clevenger 1916) ... 

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