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.