Activated Lignite (HOK) for clean drinking water in Ruhr region

The "Mulheim process" uses HOK as a high-quality filter material. In the Mulheim process, the treated HOK performs various functions. Besides the actual filtration, it eliminates substances on the grain surface such as iron and manganese which have oxidized after ozone treatment as well as the ozone itself, which is introduced for disinfection and oxidation. In addition, the highly porous activated carbon -- in conjunction with the underlying sand layers -- allows the settlement of micro-organisms that is desired for subsequent biological cleaning.