RIASSUNTO
Abstract
The Nederlandse Aardolie Maatschappij B.V. (NAM) is the largest gas producer in the Netherlands. The company operates a number of gas/condensate platforms on the Dutch continental shelf in the platforms on the Dutch continental shelf in the North Sea. From 8 of these platforms produced water is discharged directly into the sea. An extensive sampling, analysis and testing campaign was carried out in 1989 to characterise physical, chemical and ecotoxicological properties of these streams.
The total volume of water discharged from the NAM platforms was about 210,000 m in 1989. The platforms was about 210,000 m in 1989. The average volume per platform was relatively small (about 70 m per day), certainly when compared to oil producing platforms The total volume of oil discharged was about l60xl0 kg, 50-70% thereof being present in the form of dispersed oil. The total volume of all organic substances including polar compounds, was about 400xl0 kg. polar compounds, was about 400xl0 kg. The complex mixture of organic and inorganic components and their concentrations in the effluents indicate, with effluent EC/LC values between 1 and 420 ml/l, an acute toxic hazard to organisms directly exposed to the discharges. Acute toxic effects are, however, not expected beyond a distance of 50 m from the discharge point. A risk of sublethal effects cannot be point. A risk of sublethal effects cannot be excluded within distances of several hundred metres to a few kilometres from the discharge points. The dissolved organic components are most points. The dissolved organic components are most probably the prime cause of the acute toxicity, of probably the prime cause of the acute toxicity, of which the volatile aromatic hydrocarbons are the most significant. These compounds were observed at concentrations of up to 480 mg/l.
Relatively high concentrations of metals were observed in the effluents. However, these metals did not contribute significantly to the acute toxicity of the streams. This suggests that metals were not present in a bioavailable form. All effluents contained components which have the potential to be bioaccumulated by organisms. potential to be bioaccumulated by organisms. Polycyclic aromatic hydrocarbons, with Polycyclic aromatic hydrocarbons, with concentrations ranging from 0.5 to 70 mg/l, were the major contributors.
Introduction
Oil and gas are produced from many relatively small fields on the Dutch continental shelf in the southern part of the North Sea. The Nederlandse Aardolie Maatschappij B.V. (NAM) operates a number of gas producing platforms and is the largest onshore and offshore gas producer in the Netherlands. The offshore gas production is about 12 billion m per year. By-products of the offshore operations are condensate and water. The condensate and the dry gas are together transported to shore by pipeline. Water is discharged into the sea; in 1989 this was about 209.000 m
Developments with regard to the prevention of pollution of the sea have resulted in several pollution of the sea have resulted in several international agreements. In the context of the North Sea, the Paris Convention (1974) applies to the offshore oil and gas industry. The quality of discharges from platforms into the North Sea is subject to several directives prepared by the Paris Commission (PARC0M). The so-called Annex Paris Commission (PARC0M). The so-called Annex A-Part l ""black-listed"" substances are not allowed to be discharged, the Part 2 ""grey-listed"" substances should be strictly controlled, and the Part 3, radio-active, substances, are to be Part 3, radio-active, substances, are to be stringently controlled in order to prevent and, where appropriate, eliminate discharges. So far only the agreed restrictions regarding the oil content of discharges have been enforced through national regulations.
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