The present work is a study of the mass transfer gas-liquid from air bubbles into water, generated by a diffuser of air, in a column of aeration, changing the air flow from 400 L/h to 2000 L/h, the level of water from 0.50 m to 1.80 m, whose taxes of superficial application of air had varied of 3.1 L/m(2). s to 15.4 L/m(2). s. Several hydrodynamics characteristics were measured, such as the velocity range of the air bubbles and their diameter, fundamental to check the mass transfer coefficient that are in literature, by using a laser equipment for non-intrusive velocimetry. After of the study of the mass transfer, it was concluded that the air flow between 400 L/h and 800 L/h and the level of water of 1.80 m was the most efficient of mass transfer, guaranteeing for these measure, into of the column in study, most quantity of dissolved oxygen.