Whole Effluent Assessment (WEA)

Introduction Refineries handle significant volumes of water, often comparable to the amount of hydrocarbons they process. In common with many industries some of this is discharged as an effluent.

Traditionally most effluent discharges have been assessed and controlled using physical and chemical properties such as pH, temperature, chemical oxygen demand and concentrations of specific components such as oil or heavy metals. This type of approach has been successful in reducing the discharge of hazardous substances and has contributed to the substantial improvements in water quality across Europe. It is particularly suited to relatively simple effluents, especially where the discharged substances have known properties, e.g. the likelihood to cause ecotoxicological impact.

As the quality of receiving waters in Europe has improved attention has increasingly turned to more subtle effects. Ultimately the aim of improving discharge water quality is to improve the condition of the receiving water, thus minimising risks to both human health and the state of the ecology. Focus has therefore shifted from the physical and chemical characterisation of water quality to its biological quality. Such biological effects measures encompass a broad spectrum from specific toxicity studies on an effluent (either before or after discharge) to monitoring the health of the ecosystem within a receiving water body such as a river or a lake.

Such techniques have been used in a limited way in some European countries for many years. They are now starting to enter the mainstream of European regulatory control and are already being used by some companies to assess their own discharges and impacts.