How Emission Limit Values (ELVs) are determined

Regardless of whether the emission is to waters, atmosphere or ground the same basic principles are applied by regulatory authorities when setting limits in licenses and permits.

-          Is there a statutory limit that must be adhered to?

-          What is the BAT guidance limit?

-          What is the impact of the emission?

Lets take an emission to atmosphere as an example:

Statutory Limit

For many sectors statutory limits apply. For example under the new Industrial Emissions Directive (IED) large combustion plants will have statutory limits applied. There limits will be seen as the maximum allowable limits and cannot be exceeded.

BAT Guidance Limits

The next test usually applied is will a specific limit comply with BAT for the sector concerned? In the case of new facilities it is difficult to argue against BAT limits being applied. However, in the case of existing facilities, BAT limits are guidance and should be used as a basis for discussion as opposed to being directly applied. The IED is firming up on the use on BAT conclusion limits in licensing.

Impact of the Emission

Regardless of the above most regulatory authorities will ask you to assess the impact of your emission on the ambient environment, In the case of our emission to atmosphere this will usually mean carrying out air dispersion modelling and comparing the results against statutory ambient limits and generally accepted guidance such as ambient limits provided by the WHO. In some cases modelling will show that ELVs lower than both the statutory and BAT limits are required in order to comply with ambient limits.

The determination of most ELVs by regulatory authorities should follow the above simplified path.