Process and a device for purifying water

A process for purifying water by removing suspended particles which comprises passing the water through a filter of an inorganic filter material of the rock-wool type, said filter material being of a thickness of about 2 cm to below 1 m and having been prepared by melting an inorganic material and forming the melt of fibers, said melt having a composition of about 80% diabase mineral and about 20% lime, at least 90% of the fibers of said material having a diameter below 15 microns, the fiber solids content of the filter material being at most 20% of the volume, said fiber material in the fully soaked condition in the filter exhibiting a compression of less than 50% when subjected to an increase of a load acting on the surface of the filter material from a starting value of 50 grams/sq. inch to an increased value of 150 grams/sq. inch, and passing the water through the filter at a flow rate of above 10 meters per hour to remove said suspended particles.