Surface Loading Rate
Overflow Rate & Particle Capture
Surface loading rate (overflow rate) — the classic clarifier design parameter and how inclined plates transform it.
Surface Loading Rate
Surface loading rate, also called overflow rate, is the upward flow velocity a particle must overcome to be captured. Any particle with a settling velocity greater than the surface loading rate is removed.
In a conventional clarifier, the surface loading rate is set by the tank plan area. Inclined plate settlers dramatically increase the effective settling area, allowing the same clarification at a fraction of the footprint.
Matching surface loading rate to the settling velocity distribution of the conditioned solids is the essence of clarifier design. Plate settlers achieve low effective overflow rates without large basins.
v_o = Q / A_effv_o = surface (overflow) loading rate; particles with settling velocity v_s ≥ v_o are captured.
Design Reference
Design Notes
Overflow = Capture
Lower overflow rate captures finer, slower-settling particles.
Plate Multiplication
Stacked plates cut effective overflow rate without larger tanks.
Uniform Distribution
Even flow across plates is essential to realize design overflow rate.
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