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7.27
CLARIFICATION
Discharge flumes
k-
Flow distribution orifices
Ik Feed box
Overflow box j-~
Floccul_ation tank

Flash mix
tank

~--~ :~ ........ Coagulant
~i ~'~ ~ ~L ~ ......
Overflow , ~ ~,~ ~
(effluent) aid

Feed
(influent)

Underflow
(sludge)
FIGURE 7.16 Plate settlers. (Courtesy of Parkson Corporation.)

Inlet Design. Inlet flow distribution is critical for efficient performance of plate settlers.
In fact, the approach to distribution is a major difference between manufacturers. Some
manufacturers feed the plates from side channels to prevent interference between the in-
coming flow and the falling settled solids. In one case the flow to each plate is controlled
by head loss through an influent orifice. In another, flow is distributed from the side chan-
nel through slots and controlled by head loss taken through control orifices as flow leaves
the plates.
A third approach provides a large space below the plates, similar to tube settler de-
sign, to minimize velocities and to design the plate outlet to induce sufficient head loss
to ensure good flow distribution. The designer should evaluate each approach as it relates
to the water to be treated and decide if one is more advantageous than another.