It's often said that a clean environment is a luxury good. Not that it's something we don't want, but something that we can only get when we're rich enough to buy it.
This is of course true, for only a wealthy and technologically advanced economy can afford to clean up all the waste created. Just as an example, think of washing trucks. Obviously there will be oil washed off them. And for a clean environment we need to extract that oil before the waste water reaches the sewage system.
Which is exactly what these Oil Water Separators do. And yes, they're the product of a wealthy and technologically advanced society.