COLOGNE, Germany, Oct. 10, 2007 -- Activated lignite (HOK) from the Rhineland is being used to ensure clean drinking water in the Ruhr region of Germany, where RWW Rheinisch-Westfalische Wasserwerksgesellschaft mbH operates six waterworks that process some 70 million cubic meters of surface water per year to make high-quality drinking water.
RWW deploys a specially treated activated carbon developed and supplied by Rheinkalk Akdolit GmbH & Co. KG under the name "Hydro-Anthrasit H." The company's range covers products for water and wastewater treatment, which are marketed worldwide.
HOK has been used ever since the late 1970s in the "Mulheim process," a river water treatment technology developed by RWW. In this process, the customary treatment steps of flocculation, sedimentation, ozoning and filtration of river water are supplemented by further chemico-biological processes. HOK has established itself in this technology as a highly efficient filtration medium with a catalyst function.
The Mulheim process uses HOK as a high-quality filter material. In this 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 microorganisms that is desired for subsequent biological cleaning.
"Owing to its special characteristics, HOK is excellently suited for use in multi-layer filters and as a basis for biological fixed-bed filters", explains Volker Niechciol, head of the Waterworks engineering and operations department at RWW. "One particular reason for using Hydro-Anthrasit H is its porous surface, which helps achieve very good results in deferrization, manganese removal and ozone elimination."
Rheinkalk Akdolit purchases the HOK required for the production of their activated carbon filters from Rheinbraun Brennstoff GmbH, the member of the RWE Group responsible for the global marketing of upgraded lignite products. HOK is produced on a raw lignite basis in the rotary hearth furnace and used as adsorbent and filtering material in waste gas cleaning and wastewater purification. With an annual capacity of 200,000 tons, RWE AG is the world's largest producer of activated lignite.
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