Process and apparatus for biological exhaust-air purification

A process for biological exhaust-air purification is characterised by the following process steps: - passing the exhaust air to be purified through a fixed-bed packing comprising inert support particles charged with microorganisms degrading exhaust air constituents, - setting the support particles in continuous or discontinuous relative motion to each other in order to partially separate or to shear off biomass grown on the support particles, - discharging the biomass separated off and - removing the clean air. An apparatus is provided which has a screen drum reactor (17) which includes a drum (21) which can be driven to rotate about an essentially horizontal axis (2), which drum has a fixed-bed packing (4), through which the exhaust air (1) flows, composed of support particles charged with microorganisms, the axis (2) being constructed as an aeration tube into which the exhaust air to be purified can be fed axially, from which the exhaust air flows radially into the fixed-bed packing (4) surrounding the aeration tube via holes made in the aeration tube wall and to which aeration tube is additionally connected a pipe (6) for feeding water to irrigate the fixed-bed packing.