Patent ID: 7189323

Claim:
Method for biological purification of water, comprising the step of: supplying water to a reactor containing carrier elements for biofilm growth, which are kept in movement in the water in the reactor and are dimensioned to be retained in the reactor by a strainer allowing discharge of the water from the reactor through strainer openings, said carrier elements having passages providing a protected area for the biofilm growth which is protected against collision with other carrier elements, wherein each carrier element has a width or diameter greater than 20 mm, the protected area is larger than 1000 m 2 /m 3 carrier element volume, the passage length in the carrier element as a mean value is smaller than 6 mm and the ratio between the passage length and the longest dimension of the inlet openings of the passages is smaller than 3, wherein each carrier element is a plate having a large diameter to depth ratio and having a plurality of through apertures forming said passages.