Run-off rain waters from the draining surfaces are collected in a dam, sized according to collected first rainfall volume.
The first rainfall waters are separated from later rainfall waters through a back-flow valve fitted with a floating control, clogging the inlet to the treatment plant when the set level is reached. Within the treatment vessel, within the relative calm created, through the back-flow valve operation, sand is removed (seattable solid decanting and at the same time oil) which profiting from the oil lower weight than water, leads to the perfect mineral oil separation through flotation.
A peculiar device traps polluting substances inside the rainfall dams, thus leading to a good waste quality, compliant with the limits forecast by the regulations in force in terms of specific parameters (mineral oils and seattable solids). Accumulated foots are periodically disposed of through self cleaning.
Once the time interval set by the regulation in force elapses, collection is provided to the final receptor (generally sewage, unless differently imposed) through a pumping system, conveying treated waters at a controlled capacity.