Abstract: A membrane filtration apparatus located in a filtration chamber has a number of membranes and an associated support structure having a plurality of input passages and output passages. Wastewater is delivered to the input passages at one side of the membranes and the output passages receive cleaned water at the other side of the membranes after it has passed through a membrane. Each of the input passages is open at top and bottom to the filtration chamber interior, but substantially closed laterally. In a method and apparatus for cleaning the filtration apparatus, gas bubbles are discharged into the wastewater below a first subset of the input passages to cause airlift induced circulation of the wastewater up through the first subset, the flow being directed across and down through a second subset of the input passages.