Wastewater polluted with light mineral oils and settleable sludge is conducted to the oil-petrol separator system via the drain system. The silt trap section of the separator facility first of all allows the solids contained in the wastewater to settle. Devices slowing the flow speed meanwhile prevent turbulences in the wastewater.

In the oil-petrol separator section of the separator system, the light mineral oil-petrol particles separate out from the wastewater by virtue of their different gravitational weight and form a layer that floats on the surface. Once the permitted layer thickness is reached, the concept ensures that the outflow is sealed by a float. An alarm system can provide an (acoustic signal) as soon as 80 % of the maximum layer thickness has been reached, informing the user that the separator needs emptying.