A method of air scouring an immersed membrane is described in this specification. The method comprises a step of adjusting one or more aeration parameters during a permeation cycle, or between a permeation cycle and a back pulse or relaxation cycle, or between successive cycles. The method may be used with a gas delivery device described in this specification in which a supply of gas is provided to a manifold with multiple ports connected to multiple conduits. The method may further comprise bringing a flow of pressurized gas into a tank to near or below the bottom of a membrane module. At about this elevation, the flow of pressurized gas is split into multiple flows of pressurized gas. Each of the multiple flows of pressurized gas is directed to a different lateral position and then released as bubbles.

An immersed hollow fiber membrane module according to an embodiment of the present disclosure includes a hollow fiber membrane bundle formed by fixing a plurality of hollow fiber membranes by a potting agent, and a module supporting unit provided at one side of the hollow fiber membrane bundle to support the hollow fiber membrane bundle, the module supporting unit having an air cleaning time delaying portion configured to delay or intermittently maintain an air cleaning time for air introduced therein and discharged out.

Methods for cleaning water filtration membranes by treatment with a DNase containing cleaning composition. Optionally the composition also comprises a biocidal and/or other enzymes such as proteases. The DNAse may be derived from Aspergillus oryzae or from Bacillus licheniformis.

A hollow fiber membrane filtration device includes a hollow fiber membrane module including a vessel having a treated water outlet and a concentrated water outlet; a plurality of hollow fiber membranes each of which separates raw water into permeated water and concentrated water, and is vertically disposed in the vessel; an upper end fixing member that fixes upper end parts of the hollow fiber membranes and is disposed at an upper part in the vessel; a permeated water chamber that is formed on an upper side of the upper end fixing member and communicates with an interior of each of the hollow fiber membranes; and a water conduit through which the raw water is supplied into the vessel. The water conduit vertically extends on a lower side of the upper end fixing member, and a plurality of ejection holes is provided on a side peripheral surface to eject raw water.

A water treatment control system includes an aerobic tank in which aerobic treatment is carried out, an aerobic tank aeration device that aerates to-be-treated water in the aerobic tank, a membrane filtration tank including a separation membrane that filters the to-be-treated water treated in the aerobic tank, a membrane filtration tank measurement instrument that measures the ammonia concentration of the to-be-treated water in the membrane filtration tank, as a membrane filtration tank ammonia concentration measurement value, and an aerobic tank aeration air volume calculation device that sets the aerobic tank aeration air volume of the aerobic tank aeration device on the basis of the membrane filtration tank ammonia concentration measurement value.

A conventional media filter such as a gravity sand filter is converted into a membrane filter. The media is removed and replaced by immersed membrane modules. Transmembrane pressure is created by a static head pressure differential, without a suction pump, thereby creating a membrane gravity filter (MGF). Preferred operating parameters include transmembrane pressure of 5-20 kPa, 1-3 backwashes per day, and a flux of 10-20 L/m.sup.2/h. The membranes are dosed with chlorine or another oxidant, preferably at 700 minutes*mg/L as Cl.sub.2 equivalent per week or less. The small oxidant does is believed to provide a porous biofilm or fouling layer without substantially removing the layer. The media filter may be modified so that backwash wastewater is removed from near the bottom of the tank rather than through backwash troughs above the membrane modules. Membrane integrity testing may be done while the tank is emptied after a backwash.

An external circulation-type hollow fiber membrane module which has a high processing capacity and which is capable of inhibiting a to-be-treated liquid within a case from flowing through a short path and efficiently bringing the liquid into contact with a hollow fiber membrane in whichever direction of a vertical direction, a horizontal direction, etc., the liquid flows. An external circulation-type hollow fiber membrane module is provided with: a hollow fiber membrane bundle; a case; and a short-path prevention body that blocks flowing of a to-be-treated liquid in a gap between the hollow fiber membrane bundle and the case, wherein a first end of the hollow fiber membrane bundle is fixed in the case, and the short-path prevention body is provided to the downstream side of a first port which is a liquid flow-in port in the case so as to project from the inner surface of the case.

A filtration apparatus according to an aspect of the present invention includes a plurality of filtration modules each including a plurality of hollow fiber membranes aligned so as to extend in an up-and-down direction, a bar-like upper holding member configured to secure upper ends of the hollow fiber membranes, and a bar-like lower holding member configured to secure lower ends of the hollow fiber membranes; a cleaning module configured to supply bubbles from below the filtration modules; a frame including a plurality of vertical frame members disposed to extend in the up-and-down direction and a plurality of lateral frame members disposed to extend in lateral directions, the frame being configured to hold the filtration modules and the cleaning module; and a plurality of lower guide rails configured to engage with the lower holding members and disposed between opposite faces of the lateral frame members, wherein at least part of the cleaning module is suspended from the frame.

A method of cleaning a membrane surface immersed in a liquid medium with a fluid flow, including the steps of providing a randomly generated intermittent or pulsed fluid flow along the membrane surface to dislodge fouling materials therefrom. A membrane module is also disclosed comprising a plurality of porous membranes (6) or a set of membrane modules (5) and a device (11) for providing a generally randomly generated, pulsed fluid flow such that, in use, said fluid flow moves past the surfaces of said membranes (6) to dislodge fouling materials therefrom.

An aeration device configured to be fitted to a membrane filtration module having membranes mounted therein. The aeration device comprises a sleeve configured to at least partially surround the membrane filtration module. The sleeve has one end adapted to engage with the membrane filtration module and another end adapted to engage with a filtrate collection conduit or manifold.