A mechanically driven agitator for use in bioprocessing comprising (a) a rotatable shaft comprising a cylindrical element having a first end and a second end, the shaft having a vertical rotational axis; (b) an impeller comprising a hub mounted on the first end of the rotatable shaft, the hub having a horizontal axis perpendicular to the vertical rotational axis of the shaft, and at least two arms extending from the hub; (c) a seal housing assembly comprising an upper housing portion, and a lower housing portion; wherein the upper housing portion comprises an upper seal assembly, the upper seal assembly comprising an upper shaft seal and an upper shaft bearing, the shaft seal, and the shaft bearing each including an annular opening for receiving the rotatable shaft, wherein the shaft bearing is fit onto the shaft; and, wherein the lower housing portion comprises a lower seal assembly, the seal assembly comprising a lower shaft seal and a lower shaft bearing, the shaft seal and the shaft bearing each including an annular opening for receiving the rotatable shaft, wherein the shaft bearing is fit onto the shaft, and the second end of the shaft passes through the lower housing portion; the lower housing portion comprising an external surface including threads; (d) a locking ring, wherein the locking ring comprises an upper face and a lower face and an opening passing through the upper face and the lower face, the opening having a surface including threads, wherein the locking ring is threadably engageable with the lower housing portion of the seal housing assembly, and the upper face is suitable for contacting an outer surface of a wall of a bioprocessing container; (e) a support flange sealably coupled to the upper housing portion of the seal housing assembly, the support flange including an annular opening for receiving the rotatable shaft, the flange having a lower face suitable for sealing against an inner surface of the wall of a bioprocessing container; wherein the lower face of the flange seals against the inner surface of the wall of the bioprocessing container and the upper face of the locking ring contacts the outer surface of the wall of the bioprocessing container when the internal surface of the locking ring is threadably engaged with the external surface of the lower housing portion of the seal housing assembly; and wherein the upper and lower seal assemblies (110; 210) each further comprise an anti-rotation device, the seal assemblies (110; 210) each further comprising a carrier housing (105; 205) comprising a carrier housing protrusion (123; 223), the anti-rotation device comprising a notch in the seal, and the carrier housing protrusion, wherein the protrusion engages with the seal and prevents rotation of the seal. (a) a rotatable shaft comprising a cylindrical element having a first end and a second end, the shaft having a vertical rotational axis; (b) an impeller comprising a hub mounted on the first end of the rotatable shaft, the hub having a horizontal axis perpendicular to the vertical rotational axis of the shaft, and at least two arms extending from the hub; (c) a seal housing assembly comprising an upper housing portion, and a lower housing portion; wherein the upper housing portion comprises an upper seal assembly, the upper seal assembly comprising an upper shaft seal and an upper shaft bearing, the shaft seal, and the shaft bearing each including an annular opening for receiving the rotatable shaft, wherein the shaft bearing is fit onto the shaft; and, wherein the lower housing portion comprises a lower seal assembly, the seal assembly comprising a lower shaft seal and a lower shaft bearing, the shaft seal and the shaft bearing each including an annular opening for receiving the rotatable shaft, wherein the shaft bearing is fit onto the shaft, and the second end of the shaft passes through the lower housing portion; the lower housing portion comprising an external surface including threads; (d) a locking ring, wherein the locking ring comprises an upper face and a lower face and an opening passing through the upper face and the lower face, the opening having a surface including threads, wherein the locking ring is threadably engageable with the lower housing portion of the seal housing assembly, and the upper face is suitable for contacting an outer surface of a wall of a bioprocessing container; (e) a support flange sealably coupled to the upper housing portion of the seal housing assembly, the support flange including an annular opening for receiving the rotatable shaft, the flange having a lower face suitable for sealing against an inner surface of the wall of a bioprocessing container; wherein the lower face of the flange seals against the inner surface of the wall of the bioprocessing container and the upper face of the locking ring contacts the outer surface of the wall of the bioprocessing container when the internal surface of the locking ring is threadably engaged with the external surface of the lower housing portion of the seal housing assembly; and wherein the upper and lower seal assemblies (110; 210) each further comprise an anti-rotation device, the seal assemblies (110; 210) each further comprising a carrier housing (105; 205) comprising a carrier housing protrusion (123; 223), the anti-rotation device comprising a notch in the seal, and the carrier housing protrusion, wherein the protrusion engages with the seal and prevents rotation of the seal.