Dissolved Air (Pressure) Flotation-DAF, is a well established solid and/or liquid/liquid separation process that uses micro-bubbles as a carrier phase. Bubbles are formed by a reduction of pressure of a water stream previously saturated with air (gas) at pressures usually higher than 3 atm. In industrial practice, the supersaturated water is forced trough needle valves, and clouds of bubbles having 0.02-0.15 mm in diameter are produced just down-stream of the constriction. Typically 5-20 % of the water leaving the flotation tank is recycled. This process is widely used in the treatment of industrial wastewaters for the removal or separation of metal ions, anions, oil, greases, chemicals, microorganisms, colloids and ultrafines. A disadvantage of the process is the high cost of water saturation required for bubble formation. The present work shows that bubble generation is possible at working pressures lower than 2-3 aim by lowering the surface tension in the saturator and at the flow constriction. It is concluded that very low concentrations of surfactants or "collectors" ave required to make DAF now feasible at 2 aim or less, thereby reducing drastically the cost of energy and optimizing the whole process.