The sewage network

The sewage system is the complex of works that carry the waste water from our homes, in some cases industrial waste water and part of the rainwater to the water treatment plants. Waste water is carried to the treatment plants to be treated and then cleaned before “returning” to nature.

6.528 Km
of sewage networks

Waste water analysis

Treated water must be analysed and tested before being returned to the environment. This is what we do in the three company laboratories that examine the incoming and outgoing waters at the treatment plants operated by Gruppo CAP. In particular, the laboratory at the Pero plant also controls the quality of the waste water discharged from production facilities into the sewerage system. Checks are carried out in accordance with the requirements of current legislation and according to a sampling schedule submitted each year for approval to ARPA, the Regional Agency for Environmental Protection of the Lombardy Region.

More than 4000 checks are carried out each year on the treatment plants and more than 700 checks are carried out on industrial discharges. The main parameters analysed are:

  • Chemicals (COD, BOD5, Total solids, Total nitrogen, Total Phosphorus, etc.)
  • Aromatic and chlorinated solvents
  • Surfactants
  • Metals (cadmium, chromium, iron, nickel, lead, copper, zinc, etc.);
  • Microbiological (E.Coli, Salmonella, etc.)

In addition to the internal checks carried out in the company laboratories, ARPA carries out external checks in accordance with the general criteria set out by the Lombardy Region regarding plant inspections, the collection points of the samples to be analysed and the frequency of sampling.

The Pero and Peschiera Borromeo laboratories are accredited according to UNI CEI EN ISO 17025:2018 in compliance with the provisions set out by ACCREDIA Regulation RT-08 (accreditation no 697) for the tests listed below.

Water treatment

Find out the CAP Group water treatment system

Networks and citizens

We pay special attention to our customers and receive many rewards in return. Here are the results of research on a sample of 2600 customers in the territory who were asked about our services.


Satisfied with the water service


Satisfied with the sewage network