Western European refiners have reduced the oil content in discharge waters while increasing throughput.
A report by Concawe, Brussels, the oil companies' European organization for environmental and health protection, compiles data from members responding to a questionnaire on 1990 performance.
Replies represented 80% of the refining capacity in western Europe. They show a 35% reduction in the ratio of oil discharged to oil processed since the previous survey in 1987.
Oil discharge rates fell from 10.3 metric tons/million metric tons of oil processed in 1987 to 6.7 metric tons/ million metric tons in 1990. Discharges totaled 3,340 metric tons of oil from 95 refineries in 1990, compared with 4,640 metric tons from the 89 responding in 1987.
Since the first Concawe survey in 1969, which reported 44,000 metric tons of oil discharged in effluents, there has been a 92% reduction. Now 80% of the surveyed refineries have biological treatment for effluent.
Throughput in 1990 was 511 million metric tons, 14% higher than in 1987. The amount of discharge of effluent has risen marginally to 1,782 million metric tons/year from 1,750 million metric tons/year since 1987 because more refineries reported.
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