What Does This Mean and How Should This EQS Be Used?

The two main uses of an EQS are compliance assessment and permitting. For a compliance assessment the arithmetic mean concentration of “bioavailable nickel” for a site is compared against the EQSbioavailable. Some member states will also assess the “confidence of failure” of an EQS so as to provide statistical certainty to any resulting regulatory decisions (ISO/WD 5667-20). However, many Member States do not consider this, meaning that the EQS is treated as a legally binding regulator limit.

Under the WFD, compliance with the EQS for nickel is a component of chemical status. If the EQS for nickel is exceeded then the waterbody will be classified as not achieving Good Status, irrespective of the ecological quality measured in a waterbody, or the concentrations of other priority substances, and would be reported to the European Commission. This is known as the “one out, all out” principle.

The revision of permits taking into account the new EQS is likely to have a profound effect upon nickel producers and downstream users. Permits are generally set in such a way that the EQS would not be exceeded in any effluent receiving water (after due consideration of mixing zones). Where there are multiple dischargers within a catchment or waterbody this may mean that each discharger is only allowed to contribute a proportion of the EQS. Existing background levels may also be considered. Some authorities may set permits or consents to discharge on the basis of achieving no more than one tenth of the EQS in the receiving water.

However, not all the uses of an EQS are tied to the WFD and there are numerous ‘localized’ examples were site prioritization and hazard assessment may be performed in order for regulators to target resources (e.g., Environment Agency 2011).