Determining ecotoxicity drivers and biodegradation kinetics of discharged chemicals in produced water from oil and gas extraction in the North Sea

Since the late 1990’s the “zero harmful discharge” regime related to offshore oil and gas extraction has been implemented on the Norwegian Continental Shelf. It has also gained traction in other areas of the North Sea due to OSPAR regulations. However, the holistic understanding of ecotoxicity drivers and biodegradation kinetics of this complex mixture is still lacking. The main goal of the MERIT project (Intelligent testing strategy for Minimizing EnviRonmental ImpacTs of produced water) was to develop a method for the quantitative estimation of drivers and the potential for reducing environmental impacts to acceptable levels. We summarize the findings of the project with focus on 1) identifying ecotoxicity drivers through whole effluent testing supported by toxicity identification evaluation and 2) determining environmentally relevant biodegradation kinetics of discharged chemicals in produced water. We present a testing strategy using empirical data and samples from five different platforms in the North Sea to align with the goals of minimizing environmental impacts of produced water.