What is Emulsified Oil and where does it come from?

Emulsified Oil Filtration

A. Definition of Terms

1. Emulsified Oil

An oil in water emulsion is defined as a colloidal suspension of a liquid within another liquid. A colloidal suspension is a concentration of particles or droplets homogeneously dispersed through the carrier liquid (water). This occurs when the oil droplets are reduced in size to 20 microns in diameter or smaller. At this size, the oil’s normal electrical repulsion of the water molecule is overcome due to it’s minute size.

Oil in water emulsions may contain a variety of oil types and concentrations, as well as various types of solids contaminants. The oil in water emulsion is maintained through mechanical and/or chemical means.

2. Free Oil
Free oil are those droplets that are larger than 20 microns in diameter. They display a distinct phase difference and float in water in accordance with Stoke’s Law.


B. Emulsions are created in two ways:

1. Mechanical emulsions: In mechanical emulsions, a common method of creating the emulsion is by violent mixing or shearing of the oil droplet in the waste stream with a high shear transfer pump, vigorous mixer, pressure washer or other device that might disperse the oil droplets into minute droplets. Given enough time, the mechanical emulsion may break without any treatment. But with most processes and manufacturing time frames, this may be too long for practical use.

2. Chemical emulsions: Chemical emulsions are created when a surface-active chemical or chemicals are used, such as alkaline cleaners containing surfactants, soaps and detergents having ionic or non-ionic characteristics. These chemicals interfere with the natural coalescing of oil droplets and generally creates a permanently stabilized emulsion with little chance of breaking by itself.

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