What Are Oil Water Separators, and What Are They Used For?

Oil-water separators have several benefits, including minimal operating and maintenance costs. Recovering oil from the process can offset the initial costs of a separator system. They operate as an application of Stokes’ Law, which governs the settling of solid particles in liquids.

Coalescing oil/water separators

Oil and water are notoriously difficult to separate. The solution is to use coalescing oil separators. These devices use media packs that attract and collect suspended oil droplets, colliding to form larger droplets. This method is a quick, simple, and effective way to get oil from water.

The Clean Water Act (CWA) governs the discharges of hydrocarbons and oil in water. Any release of a substance into the water that does not meet the Clean Water Act’s regulatory requirements is illegal. Coalescing oil water separators North Carolina is mandatory for many automotive maintenance facilities. Oil can be present in various forms, including free oil, mechanical dispersions, and chemically stabilized emulsions. Additionally, oil can adhere to particulate materials, resulting in a high oil concentration in wastewater.

Class II oil/water separators

The first thing to understand is the difference between Class I and II oil/water separators. While they may be similar in design, there are some critical differences between them. Class I oil/water separators treat the entire flow, while Class II oil/water separators bypass some of the flow. A full retention separator is best for applications where the flow is high, and there is a risk of a spill or overflow. Bypass separators treat a small percentage of the flow and are generally used when environmental pollution risks are low.

Regular maintenance and servicing are essential for O/WSs. In addition to regular inspections, the separator must be serviced annually and cleaned after a big storm. According to Woodward-Clyde Consultants, the walls must be cleaned before the end of October. Clean coalescing plates can be washed in situ or after removal. During these cleaning processes, it is best to have someone on-site with the necessary knowledge to clean the separator properly.

Enhanced gravity separators

The basic concept behind the oil-water separation is simple: the settling of solids in liquids and the rising of insoluble lighter liquid droplets in heavier liquids are governed by Stokes’ Law. These processes involve gravity as the dominant force. But real-life conditions differ from the ideal model. That’s where enhanced gravity separators come into play. They use additional calculations to capture the essential separation parameters.

A typical configuration has three chambers in an enhanced gravity separator. These chambers are arranged in a parallel-plate fashion, creating a more efficient separation process. In addition, coalescing plates can be incorporated into the design to increase surface area and minimize plate plugging. On the downside, these require more maintenance and cost.


In recent years, hydrocyclones have come into their own as a viable technology for de-oiling produced water from offshore platforms. These devices are based on the principles of physical chemistry to separate dispersions, which are highly concentrated or relatively diluted. In addition to being excellent liquid-liquid separators, they can also form an emulsion when the Reynolds number is high. As a result, many practical commercial designs have emerged for de-oiling produced water from offshore platforms. These devices were developed to be used as downhole oil/water separators (DOWS) in the field. However, they were soon abandoned due to the safety risks involved with this technology.

Although hydrocyclone separation efficiency varies from facility to facility, it is generally considered to be above 90 percent. This is because the oil-water separation efficiencies of the hydrocyclone separators depend on the flow rates, temperature, and impurities present in the water. For example, conventional oil-water walls function at 40-60 microns. For this reason, it is essential to understand how hydrocyclones work.