A fluid transfer assembly for single use bioreactors includes a fluid transfer housing that can be mounted to the impeller shaft using a bearing that places the fluid transfer assembly directly below the lowest impeller but allows the impeller shaft to spin inside independently of the fluid transfer assembly. A fluid conduit connects the fluid transfer housing to a port in the single use bag wall which allows fluids to be introduced into the sparger and which also helps prevent the fluid transfer assembly from rotating with the impeller shaft.

An apparatus for treating fluids such as waste streams with improved aeration efficiency and dual function operation has a blower-assisted aerator, an impeller, a baffle structure circumscribing an air line that includes a first baffle and a second perforated baffle downstream from the first baffle, and a liquid reservoir containing a liquid. The impeller is fully submerged, and located upstream of the fully submerged baffle structure. A fully submerged air outlet is located downstream of the baffle structure, preferably in close proximity to the perforated baffle. When the blower is stopped and the impeller rotating, the baffle structure prevents aspiration into the liquid. In some embodiments, the baffle structure is removably affixed to an air outlet from the blower-assisted aerator, and so may be applied to pre-existing blower-assisted aerators. In some embodiments, one or both of the first and second baffles may resemble flat, domed, cupped, or hemispherical washers.

A fluid transfer assembly for single use bioreactors includes a fluid transfer housing that can be mounted to the impeller shaft using a bearing that places the fluid transfer assembly directly below the lowest impeller but allows the impeller shaft to spin inside independently of the fluid transfer assembly. A fluid conduit connects the fluid transfer housing to a port in the single use bag wall which allows fluids to be introduced into the sparger and which also helps prevent the fluid transfer assembly from rotating with the impeller shaft.

A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.

A method and apparatus for injecting a gas into a liquid in which a rotating helical impeller within a draft tube submerged in the liquid creates a liquid flow within the draft tube. Gas bubbles are injected into the draft tube either above or below or alongside the helical impeller or in all three locations. The liquid is drawn into the draft tube with a superficial velocity greater than a substantially uniform terminal ascent velocity of the gas bubbles to allow entrainment of undissolved gas bubbles in the bulk liquid into the liquid being drawn into the draft tube. The gas bubbles are injected with a uniform diameter of between about 10.0 microns and about 1.0 millimeters. The small bubble size enhances the dissolution of the gas into the liquid and also allow the entrainment of the gas into the liquid being drawn into the draft tube.