Lamella Clarifier Theory of Operation

Lamella pack in a Lamella Clarifier is consisting of a series of closely spaced flat plates inclined at an angle 45-60° from horizontal. Wastewater with insoluble solids enters the plate pack and flows between the plates. The path length, plate spacing, and angle of the plate are the usual engineering variables.

As the water flows between pairs of plates, the heavy solids with a specific gravity larger than the surrounding water will settle onto the top surface of the lower plate, and slide down the inclined surface to be collected into sludge hopper. Clear, near solids-free water then exits the top of the plate area and flows over an adjustable weir.

The settling pattern of a discrete particle in a rectangular basin is that, as the particle settles, it is carried forward by the velocity of the liquid flow through the basin. Thus, if V_f is the velocity of fluid, V_s the settling velocity of the particle, L the length of the basin, and d its depth, then a particle at the influent will settle to the bottom of the basin only if:

L/V_f=T=d/V_s
Then, we can get: V_f = V_s*L/d

Therefore, the flow velocity at which a basin can operate successfully is directly proportional to the length of the basin, and inversely proportional to the depth. This scenario applies to horizontal plates as well as rectangular basins. In horizontal plates, a particle must fall a few centimeters. In a rectangular basin, a particle may must fall 1-2 meters. The more even the flow the more efficient the settling process. Horizontal plate settlers are spaced 50-100 millimeters apart; therefore, the particle only needs to travel vertically 50-100 millimeters.