Milan is the second most populous city in Italy, after Rome. The city and its metropolitan area host more than 3,2 million inhabitants.

Metropolitana Milanese S.p.A. (MM Spa) is responsible for the Water Service of Milan, handling groundwater uptake, purification, distribution, wastewater collection and treatment and, in general, the maintenance and investment plan of the water supply and wastewater networks.

Underground water is polluted with chemical solvents and nitrates. The new drinking water planted, located via Feltre, was designed to treat this contamination. Suez, on behalf of MM Spa, has selected a process based on biological nitrate filtration.


Biological denitrification is a very reliable and performant solution for drinking water treatment.


Biological denitrification involves the biological oxidation of organic substrates in water treatment using nitrate or nitrite as the electron acceptor instead of oxygen. In a drinking water treatment plant, denitrification is carried out in just one step inside an anaerobic bio-filter filled with the filter media Filtralite® Pure which is the optimum carrier for the denitrification biofilm. The system is simple to design, very reliable, highly performant and with low operational cost.

Nitrazur®, a Suez patented process, works with a vertical flow and specific underdrains, and the biofilm develops on Filtralite Pure HC 2,5-5. This Filtralite solution offers an important specific surface area and allows a drastic removal of these pollutants.

360 m3 of Filtralite Pure HC 2,5-5 were shipped from Norway to Milan in big-bags. The plant is located downtown, therefore storage and implementation constraints were important. We worked with a specialized service provider (Palm Environnement) to install the products with hydro-ejectors in a complex configuration. More details in the video below.