Abstract: A process for the separation of foreign matter from a liquid, which process comprises mixing a stream of contaminated liquid containing dissolved gas with a stream of induced gas to provide a multi-phase flow, subjecting the multi-phase flow to turbulence and shearing thereby to produce a well dispersed bubbly liquid stream, passing the bubbly liquid stream into a vessel which contains the liquid contaminated with foreign matter, below the free surface of the liquid, and allowing the bubbles of gas to rise to the surface of the liquid, the surface adherence between the gas bubbles and the particles of foreign matter causing the particles of foreign matter to float to the surface of the liquid.