STUDY OF ECOLOGICAL RISK ASSESSMENT OF PAHS AND PHENOLS IN PRODUCED WATER AFTER PARTITIONING IN THE WATER PHASE

摘要

The impact of produced water from oil and gas operations is not only a function of its chemicalcomposition but also of the receiving environment (e.g. marine versus freshwater organisms, high energyversus low energy water etc…). The resulting toxicity of produced waters is related to chemicalcompositions, and varies widely from nontoxic (LC50>100 % whole effluent) to moderately toxic (LC50<1 %whole effluent). The impact of produced water tends to be chronic rather than acute and thereforedetermining the agents in the produced water with the greatest impact has proved difficult, particularly inoffshore operations where dilution is rapid. However, the polycyclic aromatic hydrocarbon (PAH) fractionin the oil present in the produced water has been proposed as toxic agent.In general, regulations prohibit the discharge of produced water containing more than 40 mg/L of oil. Thepurpose of this paper is to determine the effect of PAHs and phenols in produced water that tend topartition in the water phase once discharged to the ocean, as these compounds will be more readilybioavailable and therefore toxic.. Experiments with produced water from the Hibernia offshore platformhave been performed at Memorial University. The produced water contains dissolved and dispersed oil.In these experiments, the relative amount of PAH and phenol which partition into the water phase afterthe dispersed oil was separated, was measured.The results were then used to determine what the hazard quotient (HQ) is for each of the identified PAHsand phenols in the water phase. A hazard index (HI) for PAHs and phenols, which is the summation of allhazard quotients, was then calculated. The HI gives an overview of the worst-case estimated hazard ofPAHs and phenols to the marine environment. The results from this experimental study are useful inecological risk assessment of produced water in the marine environment and human.