Solving Oil Water Separator Problems

Contact Us!


  • This field is for validation purposes and should be left unchanged.

Vehicle Maintenance Facilities Oil Water Separator Design

Vehicle Maintenance Facilities Oil Water Separator Design

Vehicle Maintenance Facilities Oil Water Separator Design is increasingly important when helping meet ever stringent environmental regulations. Some facilities have water effluent streams flowing directly into lakes and rivers; subsequently, under the Clean Water Act (CWA), these facilities need permits for discharging their effluent streams.

Other facilities with discharges to sanitary sewer facilities, require permission from the sewer facility authorities for discharging to the sanitary sewer because sewer facilities required permits govern their effluent water to surrounding lakes and rivers.

Clean Water Act (CWA)

The basic law covering oil in water discharges is the Clean Water Act (CWA). Although the CWA  primarily controls discharges from Publicly Owned Treatment Works (POTWs or sanitary sewer plants) and toxic discharges from industrial plants, it also governs discharges of petroleum and other hydrocarbons into the waters of the United States. Any discharges other than those covered by the permit are illegal.

Vehicle Maintenance Facilities


A number of vehicle maintenance facilities applications require coalescing oil water separators. Car washing stations, oil change shops, military vehicle or mining and industrial equipment stations, and larger automotive repair facilities produce contaminated wastewater.

Inevitably private autos, large trucks, military or industrial vehicle diesel and gasoline engines leak oil. Most of the contamination comes from oil leaks or spills but washing work area floors and removing residual oil also adds to the contaminated water.


Stokes’ Law

Oil water separators operate using Stokes’ Law. Get more detail information in the How Oil Water Separators Work and How to Use Them paper.

Oil water separation is different from the settling separation of solids. Oil droplets coalesce into larger, spherical droplets, while solids agglomerate into larger masses, but they do not coalesce into particles having lower surface to volume ratios (like oil). The oil droplets follow Stokes’ law as long as laminar flow conditions exist.

Multiple Angle Plate Separators

Several different systems remove of oil from water; however, multiple angle plate separators are the most effective. They take full advantage of the effects of gravity for optimized oil removal. Vehicle maintenance facilities greatly benefit from using multiple angle plate separators.

What to Select

Consider several factors when selecting and designing vehicle maintenance facilities’ oil water separator systems. These include:

  • Water flow rate and conditions
  • Operating water temperature
  • Amount of oil present in the water
  • Oil specific gravity

Estimate some of these factors when no other information is available.

Above Ground Oil Water Separators vs
Below Ground Oil Water Separators

Operations requirements dictate the separator design. The more cost-effective solution are below ground precast concrete separators. Below ground systems are often retrofitted with the media installed in frames. This is both for ease of installation and ease of later service. The captured oil is self-removing to the surface, but solid particles can accumulate in the media resulting in the need for physical removal.

What is Ahead for the Future

Choose the system that will work in the future since environmental regulations continue to become stricter and require lower concentrations of hydrocarbons in effluent water. API type systems are inadequate to ensure proper treatment so it is necessary to utilize a high-efficiency system for oil removal. Multiple angle coalescing plate separators ensure effluent water quality that meets or exceeds the requirements for federal, state, and local regulations. These specially designed systems have proven sustainability under difficult conditions and continue to benefit a number of different operations.