Liquid-solid segregation

TABLE 3.3-1 Relative CapiUl Costs of Liquid-Liquid Separators 

As for gas-liquid and gas-solid systems, the liquid depth must be sufficiently great to minimize the suspending eflects of tuibuient liquid flow. As discussed in Secthm 3.2, the particles will not be resuspended provided the flow velocity is less than about 20 times the tenninal velocity. To be conservative the flow velocity should be 10 times the particle tenninal velocity. Thus, the flow area (Ar) is given 1  

For an example of 10 im particles of specific gravity = 3, Are tenninal velocity is 0.033 ft/s. To separate these particles and all laiger particles from a water stream of 1(X) fl /min (833 gal/min), the basin dimensions are calculated as follows  

In actual practice the effects of turbulence and other nonunifbrm flow characteristics would necessitate making the basin at least 19 ft long. 

Slurries exhibiting Type II behavior are sufficiently thick and flocculent that the solids tend to settle as a mass, giving a rather sharp line of demarcation between the clear liquid overflow and the settling solids. For such systems the design is normally controlled by the thickening capability of the basin, although the basin design must be adequate to provide sufficient overflow area to clarify the liquid overflow. 

Open-trough separators (API type) Plate separator devices 

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Fig. 4 Profiles of a species diffusing from the bulk liquid towards segregated biophase, (a) Biofilm on an impervious particle, (b) Aggregated cells or entrapped cells beads (c) Biofilm on a porous particle. qP dye concentration on the solid phase...

Segregation effects at the liquid-solid interface are controlled by the equilibrium distribution coefficient, k q, which is defined as the ratio of the solidus and the liquidus concentrations in atomic fractions ... 

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