D6157-97 – Standard Test Method Technical Guide

ASTM D6157 – 97 (Reapproved 2024) establishes a standardized testing practice for determining the performance of oil/water separators when challenged by a sudden, large-volume release of hydrocarbons. This protocol provides a repeatable methodology for evaluating separator efficiency under shock loading conditions, simulating scenarios such as accidental spills or process upsets where pure or highly concentrated hydrocarbons enter the influent stream.

📐 Scope and Applicability

This practice defines the testing procedure, necessary apparatus, and sampling techniques required to characterize separator performance during a sudden release event. It is critical to understand the specific boundaries of this standard:

• Excluded Scenarios: The standard does not apply to surface runoff from rain (refer to Practice D6104), mechanically emulsified influents from pumps, or the handling of debris and suspended solids.
• Chemical Exclusions: It does not address the removal of soluble organics (BTEXs), detergents, surfactants, soaps, or water-soluble salts. The effects of such chemicals may be investigated separately by adding them at predetermined constant concentrations.

⚙️ Test Procedure and Environmental Controls

The standard mandates specific protocols to ensure test repeatability. Key among these are stringent controls on water temperature and influent preparation. A standardized means for mixing oil and water is required to ensure consistent oil particle size distribution, although no specific lower limit on particle size is defined.

Temperature Requirements: Performance characterization requires testing at two distinct water temperatures to assess the effect of thermal conditions on separation efficiency. The selected temperatures must be at least 10 °C (18 °F) apart, operating anywhere within the overall range of 0 °C (32 °F) to 50 °C (122 °F). The standard explicitly prohibits variation of pH or temperature during a single test run.

📊 Comparative Test Media and Data Handling

To standardize performance comparisons, the practice adopts two specific reference hydrocarbons: No. 2 fuel oil and SAE 90 lubricating oil. All test results are directly applicable only to these media at the tested concentrations. The standard defines their properties precisely.

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