The whole system treats about 18000 m3/d (more than 60000 p.e.) and a part of the effluent is reused in a nearby industrial area. All the new sections have been provided with an online monitoring system, in order to reduce as much as possible the energy consumption for the denitrification process leaving more role to the final wetland whenever it obtains sufficient performances. The upgraded WWTP is operating since January 2003; after the first year of operation a good development of the macrophytes communities has been observed. The hybrid constructed wetland system consists in a first sedimentation pond with a volume of 2000 m3, a 1 hectare horizontal Submerged Flow System (HF) and finally a 5 hectares Free Water System (FWS). The accumulated sludge in the sedimentation basin are periodically pumped in a wet woodland planted with Populous alba.