In this paper, the dry filtration process is described. In the experimental part, the results of tests on the semi-technical scale are presented. Additionally to the determination of material parameters and characteristics of different filter materials, their back wash characteristics are examined. The biofilm on the filter material desired in wastewater technology causes a reduction of 20% of the necessary back wash velocity. On the other hand, mixing phenomena in dual-media filters were increasingly observed. The tests concerning nitrification performance showed that the dry filtration system is an extraordinarily efficient process. Volumetric degradation performances of up to 1.5 kg NH4-Nel/m3d were achieved. Volumetric load and filter velocity turned out to be decisive measurement parameters.

In the second part of this paper a dry bed filter plant on a large- technical scale of a municipal wastewater treatment plant is presented. The plant is described, operating results are discussed and operating problems are discussed

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