The application of screening tools for environmental hazard and risk to support assessment and subsequent prioritisation of effluent discharges from the oil and gas industry

Assessment and management of effluent discharges are key to avoid environmental deterioration. Often compliance with discharge regulations and permits is based on a limited set of chemical parameters, while information on whole-effluent hazardous properties (toxicity, bioaccumulation potential, persistence) and environmental risks is lacking. The need to collect those data and to become more effective in quickly identifying high risk activities, without extensive laboratory testing, has led to the development of screening tools to complement information on chemical composition. A simple, Tier-1 screening 'Toolbox' is proposed which is comprised of Solid Phase Micro Extraction with Gas Chromatographic analysis (SPME-GC), the in-vitro ecotoxicity assay Microtox and a simple weathering assay. When combined with dilution modelling screening level risk assessments can be performed providing additional lines of evidence to support a Weight of Evidence type of analysis. This enables prioritisation of discharges that may be deemed to require higher tier assessment. The Toolbox was trialled on a number of produced water samples collected from offshore oil and gas facilities and effluents from petroleum processing and manufacturing sites. In contrast to what has been reported for petroleum products, results showed only moderate correlation between bioavailable hydrocarbons (bHC) and toxicity, which might be related to the possible presence of toxic contaminants from other chemical classes or to methodological issues such as sub-optimal conditions during transport. The methods employed were quick, inexpensive and simple to conduct. They require relatively small volumes of sample, which is especially advantageous when evaluating discharges from remote offshore facilities. The Toolbox adds valuable information on whole effluent properties to existing data e.g. on chemical composition which can improve understanding of which discharges are more likely to pose a risk to the environment and so require further investigation or risk management. This article is protected by copyright. All rights reserved.