Milan San Rocco wastewater treatment plant (Italia)

wastewater treatment plant Milan San Rocco

Located in a protected agricultural estate south of Milan, between the districts of Rozzano and Opera, the plant is fully compliant with the principles of sustainable development. Its versatile structures can accommodate exceptional stormwater loads and practically all the treated water can be reused for farm irrigation.

The plant’s strongest point is the simple design of its treatment process. The activated sludge technology adopted is a tried and tested method already used in many facilities. In this specific application, it is further optimised by a biological treatment stage (step feed and alternating zones processes).

wastewater reuse

With this solution, treated water not only significantly exceeds the requirements of current regulations but is also in line with foreseeable legislative changes. The final step in the treatment chain, disinfection by ultraviolet radiation, produces water suitable for agricultural irrigation at a rate of 14,400 m3/hr in the dry season, making a significant contribution to water resource conservation.

sludge as fuel

SUEZ has taken the principles of sustainable development even further, introducing a sludge drying stage to reduce sludge volume and improve traceability. The polluted air is extracted and deodorized in two scrubbing towers, making the facility even more readily acceptable to local people. The plant has no odour or auditory or visual impact on the neighbourhood or the natural environment.

treatment lines


  • Preatreatment:
    • screening
    • 4,900 m3 grit and grease removal tanks
  • Biological treatment : step feed activated sludge system
  • Filtration:
    • 10 Aquazur® V (1,564 m2)
    • Densadeg® settling tank (wash water)
  • Disinfection: final treatment by ultraviolet radiation


  • sludge thickening by GDD® direct thickening screen
  • mechanical dewatering with plate filter press
  • thermal drying (final dry content 65-90%)

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