ASTM D6157-97(2011)

The Clean Water Act promulgated the implementation of water quality standards and contamination limits for a wide range of pollutants including oil and grease. Specifically, the USEPA, in 40 CFR Ch. 1, prohibits “the discharges of oil that cause a film or sheen upon or cause discoloration of the surface of the water. . .” Several state and local agencies have adopted this statement in addition to setting concentration limits, that is, 15 mg/L or even 5 mg/L. The purpose of this practice is to evaluate the performance of a separator in regards to the regulations and user requirements when subject to a sudden release. The sudden release may occur in dry weather and local personnel may attempt to hose the contaminated area down or it may occur on a rainy day and enter the separator mixed in with the runoff.

This practice is not applicable if the influent to a separator is simply runoff from contaminated rainwater. For this case, see Practice D6104.

This practice is not applicable if the influent to a separator is conveyed by a pumping means.

1.1 This practice describes the testing procedure, any necessary related apparatus, and the sampling technique to be used in determining the performance characteristics of an oil/water separator subjected to the sudden release of a relatively large quantity of hydrocarbons that may appear in its influent in pure form or at high concentration.

1.2 This practice does not address the determination of the performance characteristics of an oil/water separator subjected to surface run-off resulting from rain water draining from improved or unimproved land. In this case, refer to Practice D6104.

1.3 This practice does not address the determination of the performance characteristics of an oil/water separator subjected to a mechanically emulsified influent such as provided by a pump.

1.4 This practice does not investigate the ability of the separator to handle debris or suspended solids, that is, grit or tree leaves.

1.5 While the effluent may meet code requirements for total oil and grease content, this practice does not address the presence of soluble organics, that is, benzene, toluene, ethyl-benzene and xylene (BTEX's) that may be detected in the effluent. It also does not make any provisions for the effects of detergents, surfactants, soaps or any water soluble matter (that is, salts) or any portion of an essentially insoluble matter that may be found in solution on separation. (Effects of certain water soluble chemicals or solids may be investigated by adding them to the water at predetermined constant concentrations.)

1.6 In order to estimate the effect of water temperature on the performance of the separator, the tests described in this practice must be performed at two water temperatures. The selected temperatures must be at least 10 °C (18 °F) apart, with the temperature ranging from a minimum of 0 °C (32 °F) to a maximum of 50 °C (122 °F).

1.7 This practice does not make any provisions for the variation of pH or temperature during a test run. Refer to Appendix X1 for further detail.

1.8 This practice can be used with a variety of hydrocarbons. It adopts No. 2 fuel oil with a density of 845 kg/m³ (52.73 lb_m/ft³) and a viscosity² of 1.9 to 4.1 centistokes at 40 °C (104 °F) and SAE 90 lubricating oil with a density (See SAE J313) of 930 kg/m³ (58 lb _m/ft³) at 15.5 °C (60 °F) and a viscosity (See SAE J306) of 13.5 to <24 centistokes at 100 °C (212 °F) as the comparative testing media. It is understood that the results obtained from this practice are only directly applicable to No. 2 fuel oil and SAE 90 lubricating oil for the tested concentrations and only careful interpolation or extrapolation, or both, is allowed to other hydrocarbons. Low viscosity or high density hydrocarbons or hydrocarbons that contain a larger fraction of highly soluble compounds may need to be tested separately.

Note 1—No extrapolation outside the range of the tested influent or effluent oil concentrations is allowed as performance may not be linear. Hence, to establish performance at a higher or lower concentration, the separator shall be tested for that specific condition. In addition, linearity must be established prior to using linear interpolation.

1.9 Since regulations are based on effluent total hydrocarbon content, this practice does not set forth any lower limits on oil particle size for the evaluation of separator efficiency. However, a standardized means for mixing oil and water shall be specified to ensure repeatability. It must be noted however that smaller particles, having a greater surface area to volume ratio, rise at a slower rate than their larger counterparts. (Guide F933 requires that 20 % of all oil particles be smaller than or equal to 50 μm and IMO MEPC 60 (30) does not mention any particle size requirements but asks the user to avoid emulsion causing chemicals.)

1.10 Although the tests described in this practice intend to simulate the performance of a separator subjected to a sudden release, they do not cover all possible applications. It is the end user's responsibility to determine whether his separation requirements are within the scope of this practice.

1.11 A product different from the general description herein may be tested and found to be in compliance with the performance criteria set forth.

1.12 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only.

1.13 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.