API oil–water separator

[1] The name is derived from the fact that such separators are designed according to standards published by the American Petroleum Institute (API).

At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and chemical processes.

If floating grease forms into solid clumps or mats, a spray bar, aerator or mechanical apparatus can be used to facilitate removal.

Dissolving or emulsifying oil using surfactants or solvents usually exacerbates the problem rather than solving it, producing wastewater that is more difficult to treat.

In many cases where refineries have switched to heavier crude slates, the API separator’s efficiency has declined.

[3] The underside of each parallel plate provides more surface for suspended oil droplets to coalesce into larger globules.

[4] Since that time, virtually all of the refineries worldwide have installed API separators as a first primary stage of their oily wastewater treatment plants.

The majority of those refineries installed the API separators using the original design based on the specific gravity difference between oil and water.

[7][3] Today regulations often require API separators with fixed or floating covers for volatile organic compound (VOC) control.