Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: A method of chemically cleaning normally immersed suction driven filtering membranes involves backwashing a chemical cleaner through the membranes while the tank is empty in repeated pulses in which the chemical cleaner is pumped to the membranes separated by waiting periods in which chemical cleaner is not pumped to the membranes. The duration and frequency of the pulses is preferably chosen to provide an appropriate contact time of the chemical, preferably without allowing the membranes to dry between pulses and without using excessive amounts of chemical. In other aspects, such membranes preferably used for filtering water to produce potable water in a batch process are backwashed with a chemical cleaner substantially at the same time as the tank is being drained. The chemical cleaner is optionally supplied in pulses.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: A process for supplying bubbles to a membrane module and cleaning an aerator producing the bubbles includes, in repeated cycles, steps of producing bubbles from an aerator and reducing pressure in the aerator such that water in the tank enters the aerator.

Abstract: A method of cleaning ultrafiltration or microfiltration membranes reduces the rate of decline in the permeability of the membranes so that intensive recovery cleaning is required less frequently. In one aspect, cleaning events using a chemical cleaner are started before the membranes foul significantly and are repeated between 1 and 7 times per week. The product of the concentration of the chemical cleaner expressed as an equivalent concentration of NaOCl and the duration of all cleaning events is between 2,000 minutes·mg/l and 30,000 minutes·mg/l per week. When performed in situ, each cleaning event comprises (a) stopping permeation and any agitation of the membranes, (b) backwashing the membranes with a chemical cleaner in repeated pulses and (c) resuming agitation, if any, and permeation. The pulses last for between 10 seconds and 100 seconds and there is a time between pulses between 50 seconds and 6 minutes. Each cleaning event typically involves between 5 and 20 pulses.

Abstract: An assembly of potted filtering hollow fiber membranes has at least one bundle of permeating hollow fiber membranes that is potted in a block of potting material, and a cushioning wall extending along at least a portion of the axial length of the membranes adjacent the potting material and around at least a portion of the perimeter of the bundle. The cushioning wall can have a fixed edge adjacent the resin, and the wall can extend away from the resin in a direction generally parallel to the axis of the hollow fiber membranes. Walls of various structures including soft solid materials, non-permeating membranes and fabrics are described.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: An element of immersed, suction driven, filtering membranes has a plurality of hollow fiber membranes suspended between upper and lower headers. The lower header is movable between a first position in which the fibers are substantially elongated and second position in which the two headers are closer to each other by between 1 and 4% of the un-potted length of the membranes. The weight of the lower header is sufficient to keep the lower header in the first position in substantially quiescent water while allowing the lower header to rise to the second position in upwardly flowing water. Aerators are mounted generally below the elements and supply scouring bubbles to each element at a higher rate and then at a rate less than one half of the higher rate in repeated cycles. The cycles are preferably between 10 seconds and 60 seconds in duration. The lower header rises to the second position when bubbles are supplied at the higher rate and falls to the first position when bubbles are supplied at the lower rate.

Abstract: To pot membranes in a header, a dense, viscous liquid, suspension or, preferably, a thixotropic, water soluble gel, is placed in a header pan in space reserved for a permeate channel. A plurality of hollow fibre membranes are collected together and their open ends are inserted into the gel. A fixing liquid, typically a resin, is placed over the gel. The fixing liquid surrounds each membrane and then solidifies, simultaneously sealing the outer surfaces of the membranes and forming a plug in the opening of the header to complete the permeate channel. After the fixing liquid has solidified, the gel is removed by various means. The space initially occupied by the gel becomes part of the permeate channel after the gel is removed. In one embodiment, membranes are grouped by a cushioning adhesive which later surrounds the membranes where they exit the completed header.

Abstract: A method of chemically cleaning normally immersed suction driven filtering membranes involves backwashing a chemical cleaner through the membranes while the tank is empty in repeated pulses in which the chemical cleaner is pumped to the membranes separated by waiting periods in which chemical cleaner is not pumped to the membranes. The duration and frequency of the pulses is preferably chosen to provide an appropriate contact time of the chemical, preferably without allowing the membranes to dry between pulses and without using excessive amounts of chemical. In other aspects, such membranes preferably used for filtering water to produce potable water in a batch process are backwashed with a chemical cleaner substantially at the same time as the tank is being drained. The chemical cleaner is optionally supplied in pulses.

Abstract: To pot membranes in a header, a dense, viscous liquid, suspension or, preferably, a thixotropic, water soluble gel, is placed in a header pan in space reserved for a permeate channel. A plurality of hollow fiber membranes are collected together and their open ends are inserted into the gel. A fixing liquid, typically a resin, is placed over the gel. The fixing liquid surrounds each membrane and then solidifies, simultaneously sealing the outer surfaces of the membranes and forming a plug in the opening of the header to complete the permeate channel. After the fixing liquid has solidified, the gel is removed by various means. The space initially occupied by the gel becomes part of the permeate channel after the gel is removed. In one embodiment, membranes are grouped by a cushioning adhesive which later surrounds the membranes where they exit the completed header.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate of air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.

Abstract: A method and apparatus for chemical cleaning microfiltration and ultrafiltration membranes immersed in a tank involves backwashing a chemical cleaner through the membranes while the tank is empty of tank water. A backwash pump which drives the chemical cleaner is controlled by a speed controller which is in turn connected to a programmable logic control and, preferably pressure and flow indicators. The backwash pump is operated to supply the chemical cleaner to the membranes in pulses. The pressure of the pulses is high enough to reduce the relative size of pressure differentials between membranes or portions of membranes in varying places in the tank. The duration and frequency of the pulses is chosen to provide an appropriate contact time of the chemical, preferably without allowing the membranes to dry between pulses and without using excessive amounts of chemical.

Abstract: A method of chemically cleaning normally immersed suction driven filtering membranes involves backwashing a chemical cleaner through the membranes while the tank is empty in repeated pulses in which the chemical cleaner is pumped to the membranes separated by waiting periods in which chemical cleaner is not pumped to the membranes. The duration and frequency of the pulses is preferably chosen to provide an appropriate contact time of the chemical, preferably without allowing the membranes to dry between pulses and without using excessive amounts of chemical. In other aspects, such membranes preferably used for filtering water to produce potable water in a batch process are backwashed with a chemical cleaner substantially at the same time as the tank is being drained. The chemical cleaner is optionally supplied in pulses.

Abstract: To pot membranes in a header, a dense, viscous liquid, suspension or, preferably, a thixotropic, water soluble gel, is placed in a header pan in space reserved for a permeate channel. A plurality of hollow fiber membranes are collected together and their open ends are inserted into the gel. A fixing liquid, typically a resin, is placed over the gel. The fixing liquid surrounds each membrane and then solidifies, simultaneously sealing the outer surfaces of the membranes and forming a plug in the opening of the header to complete the permeate channel. After the fixing liquid has solidified, the gel is removed by various means. The space initially occupied by the gel becomes part of the permeate channel after the gel is removed. In one embodiment, membranes are grouped by a cushioning adhesive which later surrounds the membranes where they exit the completed header.

Abstract: A filtration process for filtering water with immersed microfiltration or ultrafiltration membranes in a batch mode includes repeated cycles comprising the steps of filling the tank to a level above the membranes, withdrawing permeate through the membranes, aerating the membranes to dislodge solids from the membranes and backwashing the membranes while draining the tank. The backwashing steps involve backwashings with a cleaning chemical interspersed with backwashings with permeate. The backwashings with a cleaning chemical follow a regimen of maintenance cleaning chosen to maintain acceptable permeability of the membranes or to reduce the rate of decline in permeability of membranes 24 over extended periods of time.

Abstract: An element of immersed, suction driven, filtering membranes has a plurality of hollow fiber membranes suspended between upper and lower headers. The lower header is movable between a first position in which the fibers are substantially elongated and second position in which the two headers are closer to each other by between 1 and 4% of the un-potted length of the membranes. The weight of the lower header is sufficient to keep the lower header in the first position in substantially quiescent water while allowing the lower header to rise to the second position in upwardly flowing water. Aerators are mounted generally below the elements and supply scouring bubbles to each element at a higher rate and then at a rate less than one half of the higher rate in repeated cycles. The cycles are preferably between 10 seconds and 60 seconds in duration. The lower header rises to the second position when bubbles are supplied at the higher rate and falls to the first position when bubbles are supplied at the lower rate.

Abstract: An aeration system for a submerged membrane module has a set of aerators connected to an air blower, valves and a controller adapted to alternately provide a higher rate or air flow and a lower rate of air flow in repeated cycles. In an embodiment, the air blower, valves and controller, simultaneously provide the alternating air flow to two or more sets of aerators such that the total air flow is constant, allowing the blower to be operated at a constant speed. In another embodiment, the repeated cycles are of short duration. Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.