PROCEDE ET DISPOSITIF DE NETTOYAGE DES FILTRES D'UNE INSTALLATION DE FILTRATION DE LIQUIDES

An improved apparatus for the cleaning of filter beds of a filtration apparatus which comprises a plurality of filter units, each of the units having an upper influent zone, a filter bed, and a lower filtrate zone, and including means for pumping liquid from all of the filtrate zones at a given pumping rate. In accordance with the invention, during the service cycle, liquid is pumped by the pump means from the filtrate zones to service, so that it passes through the filter bed in a downflow direction. When one of the filter units requires backwashing, the pump means is employed to pump liquid simultaneously from the filtrate zones of a majority of the filter units, so that the backwash rate is greater than the normal downflow rate through the filter unit. As an alternative to backwashing a minority of the filter unit with liquid from the majority of the units, or in addition thereto, the increased backwashing rate can be provided by increasing the pumping rate beyond the given rate during the backwashing by using booster pump means.