Danke schon mal f�r die Antworten.
Inzwischen habe ich etwas im Eurodicautom gefunden:
rapid gravity filter = offenes Schnellfilter
Eine englische Definition:
Rapid Gravity Filter (RGF):
A filter used in water treatment which removes suspended solids from water by passing it through a sand bed, where the solids collect as a surface mat and in the sand interstices. The water should previously have been treated by coagulation, flocculation and sedimentation.
http://www.filtec.co.uk/glossary.html Habe das Ganze jetzt mit "offene Schnellfilteranlagen" �bersetzt.