Emissions to water: terms and definitions

Some indicators that describe emissions to water make a distinction between emissions to water and the burden on the surface water. What is the difference, exactly?

Emissions

Substances released from a source are covered by the term emissions. Emissions to water can be subdivided into direct emissions to surface water and indirect emissions to the sewer system. Discharges to the sewer system only reach surface water after treatment; they are therefore indirect. The treated wastewater discharged from treatment plants to surface water is known as 'effluent'. The contaminants left behind are taken away in sewage sludge.
Since some of the substances are removed by treatment or broken down in wastewater treatment plants, the ultimate burden on surface water is lower.
After heavy rainfall, there are sometimes sewer overflows. A certain amount of untreated wastewater may then be discharged into surface water.

• Discharges into water and burden on surface water in the Netherlands, 1990, 1995, 1999 and 2000

Burden on surface water

The burden on surface water is the amount that actually reaches the water. The burden consists of the sum of:

• the direct emissions;
• the effluents;
• overflows;
• rainwater drains.

It also comprises transport between environmental compartments: atmospheric deposition directly into surface water, and leaching and run-off from soil, in particular from agricultural land.
Inflows via rivers from outside the Netherlands are not included when calculating the load since the sources are located outside the country.

References

• CCDM (2002). Emissiemonitor. Jaarcijfers 2000 en ramingen 2001. Rapportagereeks MilieuMonitor, no. 6. Coördinatiecommissie Doelgroepmonitoring, The Hague.

Relevant sections and indicators in the Environmental Data Compendium

• Discharges into water and burden on surface water in the Netherlands, 1990, 1995, 1999 and 2000
• Guide to Environmental theme of Eutrophication
• Guide to Environmental theme of Toxic and hazardous substances
• Guide to 'Quality of surface water' section

Relevant information outside of the Environmental Data Compendium

• More information about these terms can be found in the Emissiemonitor (CCDM, 2002).