A new multispecies effluent test encompasses the range of responses obtained from higher order tests. The OSPAR Commission, the mechanism by which 15 governments of the western coasts and catchments of Europe cooperate to protect the marine environment of the northeast Atlantic, has been considering a risk-based approach to the monitoring of produced water discharges. It seems likely an approach using whole effluent assessment (WEA) alongside a single substance approach could be introduced in the near future. The essential element of WEA is the application of testing to a sample of the whole effluent rather than individual substances known to be within it. According to OSPAR's 2007 "Practical Guidance Document on Whole Effluent Assessment," the added value of WEA is greatest in complex effluents, which contain mixtures of chemicals or require very detailed process-specific knowledge to allow characterization. Produced water would seem to fall into that category, as it consists of both naturally occurring and added chemicals, which can include biocides, defoamers, or scale and corrosion inhibitors, and its composition varies depending on location, formation type, and stage of production. Therefore, a WEA approach to produced water testing can have the potential benefit of providing a measurement of not only the effects of substances known to be present but also unknown substances as well as the combined effects of all components.
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