How is 15ppm reached in an Oily Water Separator?

How is 15ppm reached in an Oily Water Separator?

15ppm is achieved in an Oily Water Separator by normally passing through a Two Stage Separator where in the first stage Oil/Water is passed into the coarse separating compartment. Here some oil will rise to the top of the Compartment due to its lower density, Heating Coils may aid this. 

  The remaining Oil/Water will flow down into the Fine separating Compartment and moves slowly between Catch Plates.  More Oil will separate out onto the underside of these Plates and travel outwards until free to rise to the oil collecting space. 

  The almost Oil Free Water (usually being at 100ppm at this stage) will then pass to the second stage of the separator, which is a Filter Unit comprising of two Filter Units.  

The first Filter Stage removes Physical Impurities present and promotes some Fine Separation. 

  The second Stage Filter uses Coalescer Inserts to achieve the fina, Oil/Water Mixture leaving this Stage at less than 15ppm.