Published: 2/3/2026 by Tom McKinney oil water separators wash racks

Summary

When cleaning tactical vehicles, the choice of detergent determines whether an oil/water separator (OWS) functions or fails. Standard detergents create stable emulsions where oil is chemically locked into the water, allowing it to bypass gravity separators and flow directly into sanitary sewers.

The "Quick-Release" Solution

The Department of the Army recommends "quick-release" detergents that form unstable emulsions. These cleaners allow the oil to "break" away from the water and rise to the surface within a 45-minute detention window, the minimum time required for most OWS designs [1].

Top-Performing Detergents for OWS Compatibility

The Fort Benning study evaluated 20 detergents for their "quick-release" characteristics. The following products left the lowest concentrations of residual oil and hydraulic fluid in the water after a 45-minute separation period:

Product Name	Vendor	Motor Oil (Avg. mg/L)	Hydraulic Fluid (Avg. mg/L)
Duo Power	Chemsearch	26	28
Environ	Landa	28	31
Clean All Purpose	GSA	29	25
Certified GRRR	Certified Laboratories	29	31
Clean Split	Certified Laboratories	34	22

Note: Initial oil and grease (O&G) concentrations in the study were 1,000 ppm [2].

Compliance & Technical Considerations

1. False Positive O&G Readings

Many detergents contain chemicals that are extracted by n-hexane during EPA Method 1664A testing. This can cause a "false high" reading, making it appear as though the separator has failed even if no oil is present. Specifically, products like Citrikleen and VPW SC 1000 showed significant interference in laboratory tests [4].

2. Biological Toxicity

Surfactants in detergents are inherently toxic to the microorganisms used in sewage treatment plants because they alter cell wall permeability [5].

Least Toxic: Clean All-Purpose Cleaner (GSA)
Most Toxic: Duo Power was found to be 50 to 100 times more toxic than the GSA cleaner.

3. Implementation Best Practices

Gradual Introduction: When switching to a new detergent, increase the number of users gradually to allow the biological treatment works time to acclimate to the new chemical load.

Pre-Trial Testing: Prior to widespread use, conduct local laboratory testing on diluted detergent to see if it will negatively impact your specific O&G analysis results.

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Sources

U.S. Army Public Works Technical Bulletin (PWTB) 200-1-05, "Oil/Water Separator Selection, Installation, and Maintenance."
Kenneth, L., & Hudson, A. (1998). Decision tree for improving washrack oil/water separator operations. USAEC Report No. SFIM-AEC-ET-R-98003. Aberdeen Proving Ground, MD: U.S. Army Environmental Center (Yue, 2011).
McLeod, M. (1999). Effect of quick release detergent on oil/water separators. CERL Technical Report (Yue, 2011).
U.S. Environmental Protection Agency. (2010). Method 1664, Revision B: n-Hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated n-Hexane Extractable Material (SGT-HEM; Non-polar Material) by Extraction and Gravimetry.
Kenneth, L., & Hudson, A. (1998). Decision tree for improving washrack oil/water separator operations. USAEC Report No. SFIM-AEC-ET-R-98003. Aberdeen Proving Ground, MD: U.S. Army Environmental Center (Yue, 2011).