Systems and methods for diffusing gas into a liquid are disclosed. In some cases, the methods include tangentially introducing a liquid into a cylindrical chamber having a cylindrical inner wall such that the liquid develops a spiral flow. In some cases, gas bubbles are orthogonally introduced into the liquid as the liquid flows through the chamber. In some cases, a flow of the liquid and the gas bubbles is controlled such that a ratio of a liquid flow rate to a gas bubble flow rate does not exceed values which convert non-bacteria enriched, clear water into froth. In such cases, a mixture of the liquid and the gas bubbles to exit the chamber near an output end. While the liquid can include clear water, in some instances, the liquid also includes bacteria (e.g., surfactant-producing or non-surfactant-producing bacteria) and/or bacterial nutrients that allow for improved bioremediation.