Produced water fractionation and advanced chemical and toxicological characterization using sensitive life stages of marine fish species

Produced water from the oil and gas industry represents the largest direct discharge of polluted effluents to the marine environment. Approximately 130 million cubic meters of produced water is discharged annually on the Norwegian shelf from offshore production platforms. PW-Exposed, which has focused on the toxicity of produced water to the early stages of fish, has studied PW from several platforms and found that they vary widely in toxicity. A representative produced water was studied in detail to investigate which components contribute mostly to toxicity. Fractions of produced water, which to some extent represent different component groups, were studied in detail for biological effects such as affinity for transcription factors, expression of genes at tissue level, and heart damage and deformities in fish larvae. Although it was challenging to isolate a particular fraction that caused all toxicity, we found for all biological levels that component groups that had affinity for the aryl hydrogen receptor were associated with toxicity. There are several components that have affinity for this receptor, common to most is that they are polyaromatic, and especially methylated, methoxylated, and hydroxylated polyaromatic compounds should be included in the risk assessment for produced water because they are not currently part of monitoring programs. These are component groups found mostly in the oil fraction of produced water, and therefore a reduction in the amount of oil discharged with produced water will limit the risk of damage to fish eggs and larvae. In comparison, fractions containing organic acids, alkylphenols and production chemicals showed a more limited risk of damage to fish eggs and larvae, but in combination with each other and with the oil fraction, the damage was greater than the sum of the fractions alone (mixture toxicity). Results from PW-Exposed have been presented several times a year to both authorities and industry, as well as in forums and scientific conferences.

PW-Exposed has established a workflow involving chemical fractionation and analytical chemistry coupled to screening bioassays to identify toxicity-driving components in produced water PW-Exposed has identified key component groups of produced water causing short-term toxicity and potential long-term effects on early life stages of marine fish eggs and larvae PW-Exposed has developed field methodologies to assess potential toxicity of produced water and other effluents to the marine environment using in situ fish egg exposure. PW-Exposed has provided input to industries and authorities to improve regulations, risk assessment and impact assessment of produced water discharges on the Norwegian continental shelf PW-Exposed has supported the development of software used by industries and authorities to improve environmental risk and impact assessment of produced water discharges

The PW-Exposed project addresses the urgent need identified to provide a detailed understanding of the chemical composition and toxicological impacts of the produced water (PW) routinely discharged from platforms along the Norwegian coast. The project takes on this challenge by bringing together a consortium of experienced scientists that have the analytical and toxicological knowledge and instrumentation needed for this task. The project is divided into four interlinked work packages (WPs). By utilizing a combination of standard analytical techniques, sophisticated fractionation approaches and cutting-edge high-resolution chromatography and mass spectrometry, WP-1 will provide a thorough chemical characterization of PW. WP-1 will provide a series of PW fractions, which will be tested in WP-2 utilizing an expanded in vitro toxicity screening toolbox. This will specify which component groups are the main drivers for PW toxicity and their potential involvement in different adverse outcome pathways (AOPs). Together, WP-1 and WP-2 will prioritize and select the most potent toxic fractions for the final toxicological investigations in WP-3. Here, in vivo exposure studies using embryos of both a pelagic (cod) and a benthic (lumpsucker) fish species will validate the contribution from toxicity-driving component groups at the organism level, phenotypically anchor and identify AOPs in fish life stages exposed to PW fractions. WP-4 is devoted for administration, for coordinating dissemination, and furthermore to draw on experiences with previous and ongoing NFR projects working on similar topics. Three consortium workshops are planned to assist communication and exchange of results between WPs, and to communicate with relevant end users. By directly engaging with key stakeholders such as oil companies and the Norwegian Environment Agency at these workshops, the data generated in the project will be used as a basis for improving current PW risk assessment approaches.