STP1018

    Laboratory Studies on Oil Spill Dispersants

    Published: Jan 1989


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    Abstract

    Laboratory tests of oil spill dispersant effectiveness are used around the world to select dispersants for application to specific oils. These tests are presumed, by some, to represent real sea conditions and to provide the user with a result that is representative if not identical to a real dispersant application at sea. A number of tests have been developed over the years. At this time, the two most widely used tests are the Mackay test, otherwise known as the Mackay-Nadeau-Steelman (MNS) test, and the Labofina test, otherwise known as the Warren Springs or rotating flask test. The Mackay test employs a high velocity air stream to energize 6 L of water, whereas the Labofina test uses rotation of a separatory funnel with 250 mL of water. Both tests apply a large amount of energy to the oil/water system.

    This paper compares test results from these apparatus with those from two lesser known devices, the oscillating hoop and the swirling flask. Both devices are relatively new, and protocols for their use have not been finalized. The oscillating hoop apparatus uses a hoop which is moved up and down at the water surface. The concentric waves serve both to energize the oil in the hoop and to contain it. Thirty-five litres of water are used in this test. The swirling flask test makes use of a 125-mL Erlenmeyer flask. The flask is rotated using a standard chemical/biological shaker to produce a swirling motion in the contents.

    The results obtained using all 4 apparatus with a number of oils and dispersants are presented. A total of 121 oil/dispersant combinations were tested in the 4 apparatus.

    The correlation of numeric values between the Mackay, Labofina, oscillating hoop, and swirling flask is low. The correlation of effectiveness ranking is also poor. An oil that disperses more readily than another, according to one test, is less readily dispersable according to one or more of the other tests. Similarly, a dispersant that is more effective by one test is less effective by another. The results from the oscillating hoop correlate poorly with all other test results.

    Specific tests were also conducted to ascertain the effect of settling or rising time (the time the oil-in-water mixture is allowed to sit unagitated before a sample is taken). Longer settling times alter the oscillating hoop test results dramatically, improve the correlation for results with different apparatus, and enhance correlation with physical data such as viscosity. Differences in the effectiveness results are still apparent.

    Results show that all the high energy tests (the Mackay, the Labofina and the oscillating hoop) produce unique dispersant effectiveness results and those correlate poorly with the physical properties of the oil.

    Keywords:

    dispersants, laboratory tests, effectiveness testing apparatus


    Author Information:

    Fingas, MF
    Head of chemistry and physics section and division employees, Conservation and Protection, Environment Canada, River Road Environmental Technology Centre, Ottawa, Ontario

    Dufort, VM
    Head of chemistry and physics section and division employees, Conservation and Protection, Environment Canada, River Road Environmental Technology Centre, Ottawa, Ontario

    Hughes, KA
    Head of chemistry and physics section and division employees, Conservation and Protection, Environment Canada, River Road Environmental Technology Centre, Ottawa, Ontario

    Bobra, MA
    Head of chemistry and physics section and division employees, Conservation and Protection, Environment Canada, River Road Environmental Technology Centre, Ottawa, Ontario

    Duggan, LV
    Head of chemistry and physics section and division employees, Conservation and Protection, Environment Canada, River Road Environmental Technology Centre, Ottawa, Ontario


    Paper ID: STP18663S

    Committee/Subcommittee: F20.18

    DOI: 10.1520/STP18663S


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