Making consents fairer

It would be fair to say that enforcement of discharge consents has not received the highest priority in recent years. Most tellingly, just 0.3% of them were reviewed in 2004 - an improvement on the 0.1% rate in 2002 and 2003.

This means that, as new techniques emerge to reduce emissions, there is no pressure for them to be implemented.

The Environmental Industries Commission’s (EIC) Water Pollution Control Working Group has, therefore, lobbied Defra and the Environment Agency on the issue for some time. To keep up pressure for reform, the group has now produced a paper setting out the fundamental issues regarding the setting and control of effluent discharge consents, both to sewer and to watercourse and written to the chief executive of the Environment Agency (EA), Barbara Young, to urge her to carry out a review.

The paper proposes that the current usual practice of having concentration limits and a volumetric flow limit – usually monitored separately – should be replaced whenever possible by a mass emission-based approach. Changing the basis on which discharge consents are calculated would lead to consent conditions based on better scientific basis and a fairer way forward established for dischargers and regulators.

The usual current practice of regulation is arguably acceptable for discharges that are more or less constant in volume and have little variation in composition or mass of pollutant emitted. Apart from the doubt about how these values are calculated and set, the problem with this approach is that, with the drive for reduced water consumption (which is now embodied in regulation through IPPC), the concentration of pollutants may well increase in a much reduced flow, even though the total mass of pollutant emitted into the receiving environment remains the same or even decreases.


To continue to use concentrations as the main monitored parameter and logically take into account reduced effluent flows, any particular site would have to be continually renegotiating its consent – this would be both difficult to do and often not accepted by the EA. If a mass emission-based consent were to be adopted, there would be better monitoring of environmental emissions with a sounder scientific basis.

From recent work, it appears that the EA does not always use a model approach (as suggested above) for determining concentration limits and some dubious methodologies have been encountered in assigning concentration limits. In particular, for effluents containing dangerous substances, the agency’s policy applies different approaches to new and existing discharges.

There are few emissions where it is solely the concentration of a pollutant in the discharge which requires

control and regulation. The effect on the environment and the risk to human health is almost invariably associated with the mass of pollutant emitted.

Therefore the simplest and most scientifically correct way of monitoring emission to watercourses to try to regulate and assess its effect on the environment is to use a mass-balance approach.

This should not involve significant additional work – to ensure compliance with a traditional concentration limit-based consent, the concentrations of the controlled pollutants in the discharge have to be monitored. To assess the mass emission would involve multiplying these concentrations by the flow over the period required.

Where these facilities are not already in place, or more direct measurements, for example direct toxicity measurement, are required then this may lead particular sites to have to install such equipment. Adopting the above approach would lead to a more scientifically sound approach, a fairer system and better protection of the environment.

Merlin Hyman is the director of the EIC. For more information visit

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