A fixed volume of wastewater was added from the bottom of the reactor to the liquid volume retained from the previous treatment cycle using a peristaltic pump. In the reaction phase, the filled wastewater was continuously aerated (with the exception of the first hour for denitrification) by air injection through porous stones placed close to the upper sieve and recycled through the biomass supporting material using a recycle pump, in order to obtain a homogeneous distribution of substrate and oxygen. Finally, the treated wastewater was discharged by gravity using a port located in the liquid phase over the bed through the opening of a motorized valve (duration of the drawing phase: 15 min).