METHOD OF TREATING INDUSTRIAL WATER

摘要

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-aluminium/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.