[en] A liquid-liquid contactor column has a solvent input and an aqueous phase input. Lighter phase liquid is discharged and heavier phase is moved by an air lift to a receiver. The air supply line to the air lift includes valve and a pressure sensing transducer senses pressure in line and sends electric signals to signal processing unit which may for example close down operation of the column, or effect other changes to maintain operating characteristics of the column. The column could be pulsed by means which also send signals to unit, and could deliver to an external settler. (author)