The Bever IBS (Integrated Biological System) is a decentralized wastewater treatment system that uses the vertical active sludge principle. This system is based on the Bever IIIA system but has been specially developed for applications where industrial wastewater is treated or pretreated before it is discharged at a discharge point and has a capacity ranging from 200 to 5000 p.e. (pollution equivalent) which is the average pollution of one person per day. This is approximately 135 litres household wastewater per day. All process elements are Built into one silo tank which contains several (depending on capacity) lightweight, reinforced polyester tanks, a sludge thickener and a settling tank. Because of this design the whole system is very compact allowing it to be placed in many situations.