Condensate treatment includes:

Automatic drainage of condensate collected in several places in the compressed air system.

Including compressor cooler, filter drain, refrigeration dryer, bottom of the air receiver and other low points in the system.

In many cases, drains are electronically controlled and monitor the build-up of condensate with liquid level sensors.
It detects and knows when it is absolutely necessary to empty the condensate, which minimizes the pollution of already compressed air.

Condensate treatment is also an oil / water separator which is installed as part of the compressed air system.
It simply reduces the oil concentration in the collected condensate to a level that is permissible for discharge.
See more here.

Once oil saturated condensate has been effectively removed from a compressed air system, it cannot be discharged directly to drainage without the oil content being reduced to values ​​within the legal disposal limits.
An oil / water separator is the solution to remove oil saturated condensate.

This separation allows a larger amount of pure water, up to 99.9% of the total condensate, to be discharged safely into the sewer.
And that the relatively small amount of concentrated oil is disposed of legitimately and economically justifiably.