How Oil/Water Separators Keep Wastewater Clean

Installation of an underground oil water separator.

Installation of an underground oil/water separator.

Oil/water separators are in a variety of industrial applications. They work to remove oil, grease, light petroleum products, and oily coated solids from wastewater before it’s united into municipal sewer systems. Separators keep these substances from causing environmental damage and also lessens the burden on wastewater treatment plants. On-site wastewater processing is also increasingly required due to government regulations, which underscores the necessity of oil/water separators.


The most common industrial applications for oil/water separators include water treatment at airports, power plants, and municipalities. Specifically, utilized in fueling facilities, repair and maintenance shops, and wash areas at these facilities, where oil and water typically drain together into the sewer.

How It Works

Aboveground oil water separator.

Aboveground oil/water separator.

Oil/water separators are installed between the surface drain and the main sewer line. For this example, we’ll be referring to Highland Tank’s patented oil/water separator

Wastewater enters the tank from a drain. Water is then immediately slowed by passing through a diffusion baffle. Water then proceeds through several filters in the tank. Large globs of oil immediately rise to the surface of the tank, being lighter than water.

Also, oil accumulates on the underside of a plate pack filter. The filter is designed with ridges to hold the oil. Solids collect on the plate pack. The plate pack is angled to redirect them to the bottom of the tank. The final filter catches small oil particles that are up to 10 microns in size. The rest of the oil congeals and rises to the top of the tank. A sensor in the tank alerts the operator when the oil level in the tank becomes too great, at which time the operator can pump the oil out. Treated wastewater leaves the tank with not more than 10-ppm free oil.


Tanks Direct

Tanks Direct is the leading national industry contractor who offers full-service solutions for water and petroleum storage. Partnering with you from design through construction and maintenance, we strive to be your first choice.


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