Beside biofilm, granules with average diameter of approximately 5 mm formed in an AnRBC.

In situ microbial activity of anammox and denitrification within granules were investigated with microelectrodes.

The most active zone of anammox was in the surface layer of 200–400 μm, and anammox activity increased with increasing of substrate concentration.

Denitrification activity was identified and the most active zone was limited to the inner layer of the granules.