The Microtox* toxicity test is based upon the inverse relationship between the light output of a marine luminescent bacterium Photobacterium phosphoreum and the concentration of a toxic chemical. Although this test may lack environmental relevance and hence has often been considered only suitable to be used as a screening test, it does have some advantages over many other aquatic toxicity tests. For example, it is relatively portable, sensitive, easy and quick to perform and the test organisms can be stored frozen until required for testing. These features have led to the increasing use of this test to support a variety of activities ranging from monitoring effluent discharges to assessing the toxicity of specific chemicals and contaminated sediments. Similar considerations also make the Microtox test appear a potentially attractive system to use on offshore installations where limitations in space, facilities and technical support may make it difficult to conduct other well established marine toxicity test procedures.

Therefore, various possible applications of the Microtox test relevant to the offshore oil and gas industry have been examined and discussed in this paper. These indicate that:-

  1. The Microtox test has potential to monitor discharges from offshore installations at source. This can be useful as an initial assessment of effects of changes in operational procedures on the toxicity of waste streams and, in some operational areas, predict compliance with discharge consent criteria. For the latter application the Microtox results should be calibrated for individual systems to data for other marine species.

  2. The Microtox test provides a useful screening tool for gaining a better understanding of the potential toxic interactions of oilfield chemicals which may be used as mixtures in oil and gas activities.

  3. On the basis of laboratory studies the Microtox test has potential to be used to monitor the performance of packages designed to provide antimicrobial protection (i.e. pipeline corrosion protection packages).

  4. The speed, simplicity and relatively low cost of the Microtox test may make it suitable as a quality control test for certain chemicals prior to their use offshore.

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