One or more new, or existing, or modified, open bottom bio-remediation reactors R are contained within a commercial, industrial, or municipal waste water aeration treatment facility or tank directly above existing and/or new stand-alone diffusers located on the bottom of the facility or tank. The reactors R increase solubility of air and/or oxygen in water, increase energy efficiency, increase through put of treated waste water, and improve bio-remediation of the waste water. Also, a tube reactor having no packing substrates in a non-tube area is described.