Stormwater Management: What It Is And How To Treat It On Industrial Sites

Increasing urbanisation and the associated soil sealing give stormwater management a major role in environmental protection.

In particular, proper stormwater management makes it possible to:

  • reduce pollution
  • purify water for use in agriculture, households or industry
  • reintroduce it harmlessly into the environment.

But what is rainwater and what is the correct management of these fluids in industrial and production sites and on all potentially polluted paved surfaces such as, for example, ports, airports, motorways, car parks?

Let’s find it out together.


Stormwater is part of atmospheric precipitation.

Specifically, it is rainwater that has not been absorbed by the ground but at the same time has not evaporated either, and therefore washes away the draining surfaces.

Rainwater is divided into first rainwater and second rainwater:

  • First rain water: are the first 5 mm of rain evenly distributed over the draining surface. They are considered harmful waters as they come into contact with potentially polluting agents.
  • Second rain water: corresponds to the part of the rainwater runoff in excess of the first rain water. They are not considered pollutants.

Rainwater management regulations focus exclusively on first rain waters precisely because by their nature they are potentially polluting.

Specifically, for the purposes of preventing environmental and hydraulic risks, Legislative Decree no. 152 of 03 April 2006 provides that it is the Regions that establish the forms of control of stormwater discharges.

Let’s go into more detail on first rainwater management.


As we mentioned earlier, stormwater management is specifically regulated to avoid the risk of pollution.

For this reason, those dealing with stormwater must consider the following steps:

  1. collection of first rain water: accumulation tanks allow the potentially polluted first rain water to be separated from the second rain water.
    At the same time, a first removal of the solid fraction from the flow takes place by sedimentation.
  2. First rain water purification: the heart of the purification process is the de-oiling of the flow. If necessary, depending on the pollutants present, more stringent treatment steps may be required, such as, for example, coagulation and flocculation treatments or tertiary filtration.
  3. disposal: the discharge of first rain water, in accumulation and relaunch systems such as those described, takes place at a constant flow rate. This allows the receptor (public sewer or surface water body) to absorb the flow peaks typical of rain events.

In this way, the fluids can be reintroduced into the water cycle, or, they can be used in industrial processes or irrigation.

In general, purification treatments are ideal for both rainwater purification and industrial waste fluids.

Contact us to learn more about our water treatment system.

Il futuro inizia adesso