The aim of the project is to provide the technical elements to guarantee an increase in the purification capacity of the Monza purification plant so as to allow compliance with the discharge limits.

At the outlet of the existing desanding-desanding section, a coupling well is planned which, via a complementary underground passageway, transfers the flow to be treated to a new feeding station of the project biological tanks. The new biological compartment consists of 6 discontinuous cycle reaction tanks (SBR Sequencing Batch Reactor type), by means of an aerobic granular sludge (AGS) type process: simultaneous feeding and draining, nitrification, denitrification, sedimentation. Within the AGS reactors, it is possible to achieve pollutant removal by means of nitrification/denitrification reactions and, at the same time, to carry out biological defoaming.

The new biological treatment section is designed with the biological tanks completely underground, allowing the following advantages:

• Containment of any aerosols
• Noise containment
• Odour containment

The new treatment section of the sewage treatment plant will relieve the current average inflow of about 200,000 population equivalents.

Once the biological treatment has been carried out, the water will be returned downstream to the secondary sedimentation section in the existing plant where tertiary filtration and final disinfection will take place before returning it to the Lambro river.