Immersed screen and method of operation

Abstract

A static screen has a plurality of screening bodies and a plurality of aeration devices downstream of the screening bodies. Each aeration device is associated with a set of one or more of the screening bodies. Each aeration device may be a pulsing aerator. The pulsing aerators do not all release air at the same time. Each screening body works through periods of dead end filtration separated by backwashing events. The backwashing events comprise introducing a slug or pulse of air into the bottom of the screening body. Flow through the static screen continues at all times because the screening bodies are not all backwashed at the same time. The static screen may be used to remove trash from water flowing to an immersed membrane unit. Alternatively, the static screen may be used to provide primary wastewater treatment.

Description

technical field [0001] The invention relates to a filter screen for filtering water, a method for operating the filter screen and a method for using the filter screen for water treatment. Background technique [0002] International Patent Publication No. WO 2007 / 131151 describes a static screen for use upstream of submerged membrane modules in membrane bioreactors. In some embodiments, the screen comprises a set of vertically oriented cylindrical filter bodies mounted in a storage tank. The filter body is open at its lower end and is connected to a collecting pipe near the bottom of the tank. The filtered water is collected in the collection pipe and can then be transported through the tank wall to feed the membrane modules. The aerator is located below the collecting pipe. In one process, air bubbles in the aerator are provided continuously at a low rate to discourage solids from settling on the filter. The air blow rate is periodically increased to reduce the density o...

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