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, among other things, 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 some systems, an air blower, valves and controller provide simultaneous but 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.  Transient flow conditions result in the tank water, which helps avoid dead spaces and cleans or inhibits fouling of the membranes.  WO/2000/021890 is incorporated herein in its entirety by this reference to it.