Abstract: One or more hoses (10) belong to the ventilation system which through a perforation are constructed at least partially as ventilation hose (60). Each of the hoses is permanently connected with a number of holding devices distributed over its length, which hold the hose (10) from below. The holding devices run in a guide rail (14). The hose (10) is drawn into the empty or liquid-filled basin (10) with a traction device along the guide rail (14) which introduces the tractive force onto the body of the hose and holds it there without prestress.

Abstract: A water treatment module (14) has a sedimentation compartment (20), into which water is introduced under high pressure. A filter or microsieve (1) can be provided upstream of the sedimentation compartment (20). Above the sedimentation compartment (20) there is located a flooded first fixed bed reactor (22) for microbiological denitrification, which is flowed through from below. The water travels by way of an overflow device (34) and a sprinkler system (36) through which dissolved nitrogen is stripped and oxygen enrichment from the air occurs, into a second fixed bed reactor (38) for microbiological denitrification. This is constructed as a drip device, and is flowed through by air in a chimney-like fashion. Below the second fixed bed reactor (38) is located a catch basin (44) with a drain (54).