An aeration system for treating liquid contained in a vessel is provided. The aeration system includes a header pipe and a plurality of lateral pipes coupled to the header pipe. The lateral pipes each have one or more tubular diffuser membranes sleeved therearound. Also provided is a coupling for sealingly joining end portions of two adjacent pipes is provided. The coupling includes two saddle sections and a deformable gasket extending between the pipes. The coupling is adapted for enabling one pipe to be removed and replaced from a series of pipes without substantially moving any adjacent pipes.