Filtering procedure e.g. for surface water uses filtering medium in which series of spiral recycling loops is created by suction

摘要

The procedure, using a filtering medium such as sand in a channel formed inside a tank (1) through which the liquid to be treated is passed. The untreated liquid (EB) is injected into the filtering medium at the inlet end (E) of the channel so that it travels in a series of recycling loops as it moves towards the outlet end, where the treated liquid (ET) is extracted. The loops are produced by suction applied to the undersurface of the filtering medium, drawing out the liquid so it can be re-injected at the top.