Sludge on carrier: SAF / Biorotor
Bacteria that are allowed to grow as a biofilm on a carrier can be kept in the system for longer. The resulting biofilm serves to treat the water.
Submerged Aerated Filter (SAF)
In the case of an SAF, the carrier material is submerged in the basin in the form of packing above an aeration system. This combination results in the biological treatment of the waste water. The sludge continues to grow and forms a biofilm on the carrier. We keep the thickness of the biofilm under control by means of coarse bubble aeration. By adding the air bubbles the excess is skimmed off and is separated in a sedimentation tank.
Biorotor
Another approach is the biorotor. Here, partly submerged disks overgrown with biofilm revolve slowly in a basin through which waste water flows. Oxygen is supplied via the non-submerged part of the biorotor that is in contact with the air. This is a very simple and robust technology. The excess biofilm is scummed off and then separated in a sedimentation tank.