Wastewater is treated by providing a distribution conduit and providing a diffuser assembly. An aperture is created in the distribution conduit having an initial minimum diameter. The diffuser assembly, in turn, comprises a diffuser membrane in fluidic communication with a mating tube. The mating tube has an initial outside diameter at a location along its length greater than the initial minimum inside diameter of the aperture. The mating tube is inserted into the aperture until the location on the mating tube that, before insertion, had the initial outside diameter is encircled by the aperture where the aperture, before insertion, had the initial minimum inside diameter. This forms an airtight interference fit between the distribution conduit and diffuser assembly.