The following background discussion is not an admission that anything discussed below is citable as prior art or common general knowledge. 
International PCT publication WO/2000/021890 describes an aeration system for a submerged membrane module that 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 to individual aerators.  In an embodiment, the air blower, valves and controller, simultaneously provide alternating air flows to two or more sets of aerators such that while the total system air flow is constant, allowing the blower to be operated at a constant speed, each aerator receives a flow of air that varies over time.  In some embodiments, the flow of air to an aerator occurs in repeated cycles of short duration.  Transient flow conditions result in the tank water which helps avoid dead spaces and assists in agitating the membranes.  WO/2000/021890 is incorporated herein in its entirety by this reference to it.