Oil refinery experience with the assessment of refinery effluents and receiving waters using biologically based methods.

The trend in discharges of petroleum-related substances from refineries in Europe shows a consistent picture of declining emissions, since first measured in 1969. This decline coincides with enhanced internal capture or recycling procedures and increasing use of physical and biological treatments. At the same time, and partly in response to legislative drivers, there has been an increase in the use of chronic (long-term) toxicity tests and alternative methods for assessing the quality of effluent discharges.