Lamella Settling Systems

Lamella settling systems use packs of parallel, inclined plates to obtain many times the settling surface of a conventional clarifier within the same footprint. In a system with a fixed settling velocity, separation efficiency is governed by the vertical distance a particle must travel to settle. In a conventional tank that distance is measured in metres; in the narrow channels between plates it falls to a few centimetres. The particle reaches the plate surface after a short path, then slides down the incline into the sludge zone. The result is a much higher hydraulic loading capacity for the same volume. In practice this is exploited in two ways. Where an existing plant needs more capacity, inserting lamella packs into the clarifier allows flow to be increased without building a new tank, removing both the capital cost and the construction time. On a new plant, the same performance is achieved in a markedly smaller area — decisive where land is expensive or the installation sits close to a residential area. Lamella systems are particularly efficient at separating flocs after chemical dosing. Flocs leaving the coagulation and flocculation stage are light and fragile and tend to break up over a long settling path; the short distance reduces that risk. They are widely used in surface water treatment, industrial pre-treatment and water reuse lines. In design, plate inclination, channel spacing and surface loading rate are determined together; configuring the sludge withdrawal system to prevent accumulation beneath the plates is critical to uninterrupted operation.