Method of treating industrial water

(22) 27.02.2017

(43) 16.03.2017

(57) The invention relates to a method and apparatus of removing sulphate and soluble metals such as calcium from water. The invention relates also to a method of controlling the method. The method comprises steps of a) precipitating a first part of sulphate of the water by contacting the water with a first calcium compound and adjusting pH of the water to 10.5 or higher so as to form a first sludge containing gypsum and metal hydroxides, b) subjecting the first sludge containing gypsum to electrocoagulation for precipitating a second part of sulphate as ettringite, and for precipitating calcium-luminium/iron-sulphate hydroxides, c) conducting the sludge formed in steps a) and b) to solid-liquid separation for separating precipitated solids from the water, d) neutralizing the water received from step c) to provide water decreased in sulphate and soluble metal such as calcium content.

(71) Outotec (Finland) Oy