Oil Water Separators Guide

Oil water separators are devices that use different methods to separate oil from water. Industrial pollutants from places like chemical plants, oil refineries and off shore rigs make their way into the water that results from air compression. Separators were invented to separate liquids from solids in the wastewater while leaving a layer of water behind for reuse and recycling or to reduce the amount of pollutants in wastewater drainage.

The American Petroleum Institute (API) was the first association to develop the oil water separators. In partnership with the Rex Chain Belt Company (now USFilter Envirex Products), what is now known as an API separator was established. Since 1933 after the very first separator was installed in Philadelphia, practically all refineries and plants with wastewater treatment facilities have used the API-style separators.

The original design relies on gravity for the separation of oil from water. Using physics and Stokes' Law, API separators determine the rate of which oil droplets rise while solids sink through water. This creates a layer of oil to be skimmed off the top and a bottom layer to be removed by the use of a chain-and-flight scraper and a sludge pump. What is left is a layer of wastewater which is then sent on for further treatment to remove any remaining oil and debris.

While the design of API separators functioned, there was definite room for improvement. A downside to the original design was the amount of water needed for processing which in turn required a large enough tank to house the separation. To answer this, the coalescing design was invented. Known as parallel plates or corrugated plates, the size of the tank was cut down while the process of separation generally remained the same. By offering a larger surface area in the direct channel of a wastewater stream, the efficiency of separation increased and the need for large tanks diminished.

As regulations and guidelines concerning wastewater and the environment grew more and more strict, improvements to both API and parallel oil water separators have been made. While gravity separation has remained a constant in device design, chemically-assisted separation and air flotation methods have also been used. Chemical induction units are used to increase the rate of which chemical reactions occur, thus reducing the amount of energy needed for separation. Dissolved Air Flotation (DAF) and Induced Air Flotation (IAF) are two methods often matched with parallel plate oil water separators to facilitate separation as well.

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