Standard Operating Procedure: Wash Rack Detergent Usage

1. Purpose

To establish guidelines for selecting and using detergents at vehicle wash racks to ensure compatibility with oil/water separators (OWS) and prevent National Pollutant Discharge Elimination System (NPDES) violations [1] [5].

2. The "Quick-Release" Requirement

Only "Quick-Release" (or "Separator Friendly") detergents are authorized for use at installation wash racks. These products must form unstable emulsions that allow oil to separate and float to the surface within a 45-minute detention window.

3. Approved Product List (Performance-Tested)

Based on the PWTB 200-1-47 study, the following detergents demonstrated the highest efficiency in allowing oil to separate from wash water within 45 minutes:

Note: These results are based on an initial concentration of 1,000 ppm oil and grease [2].

4. Operational Guidelines

Step 1: Proper Dilution

• Detergents must be diluted according to the manufacturer's specific instructions.
• Avoid "over-soaping," as excessive detergent concentrations can increase the toxicity of the discharge to sewage treatment plants [3].

Step 2: Washing Technique

• Use high-pressure hot water washers as the primary cleaning method.
• Apply detergents only to components heavily soiled with oil and grease that cannot be cleaned by water alone [3].

Step 3: Phased Implementation

• When introducing a new detergent, increase the number of users gradually.
• This allows the biological microorganisms at the wastewater treatment plant time to acclimate to the new chemical surfactants.

5. Critical Compliance Warnings

• False Positive Readings: Certain detergents (e.g., Citrikleen, VPW SC 1000) contain chemicals that interfere with EPA Method 1664A. This can cause your oil and grease (O&G) test results to appear higher than the actual oil concentration [4].
• Toxicity: Surfactants in these soaps are toxic to the "good" bacteria in sewage treatment systems. Of the high-performers, GSA Clean All-Purpose is recommended for its relatively lower toxicity levels.

Sources

1. U.S. Army Public Works Technical Bulletin (PWTB) 200-1-47, Detergent Selection for Use at Army Washracks.
2. U.S. Army Environmental Center (USAEC) Report No. SFIM-AEC-ET-R-98003, Decision Tree for Improving Washrack Oil/Water Separator Operations.
3. ERDC/CERL Technical Report 00-40, Designing Coalescing Oil/Water Separators for Use at Army Washracks.
4. U.S. Environmental Protection Agency (EPA) Method 1664, Revision B: n-Hexane Extractable Material (HEM; Oil and Grease).
5. U.S. Army Public Works Technical Bulletin (PWTB) 200-1-05, Oil/Water Separator Selection, Installation, and Maintenance.