Abstract: A method for the treatment of waste water to form useful water, comprising the steps of subjecting the waste water to a chemical flocculation treatment, floating the formed turbid portion of the waste water, and subjecting the clarified water to reverse osmosis filtration.The waste water treatment plant or installation for the performance of the aforesaid method comprises, in combination, apparatus for carrying out the chemical flocculation treatment, an electro flotation installation, and a reverse osmosis installation.