Abstract: Uses of a method of producing small bubbles of gas in a liquid include gas transfer in airlift bioreactors and anaerobic digesters, and particle separation. The method uses a source of the gas under pressure, a conduit opening into a liquid and oscillating the gas passing along the conduit. The oscillation is effected by fluidic oscillator, comprising a diverter that divides the supply into respect outputs, each output being controlled by a control port, wherein the control ports are interconnected by a closed loop. Separation of algae from water involves delivering a laminar flow of microbubbles in the range 10 to 100 ?m diameter. Such bubbles also deliver a laminar flow in bioreactors that delivers enhanced liquid flow despite the small bubbles, which improves mixing and also enhances efficiency of gas exchange and retention of the bubbles in the reactor.