Discharge of oyxgen-demanding substances and load on surface water in the Netherlands, 1975-2000
The burden on surface water generated by oxygen-demanding substances has fallen again. This is primarily the result of improvements in the efficiency of urban wastewater treatment plants.
| 1975 | 1980 | 1985 | 1990 | 1995 | 1999 | 2000 | ||
| million inhabitant equivalents 1) | ||||||||
| Consumers | 13.7 | 14.1 | 14.5 | 14.9 | 15.5 | 15.8 | 15.9 | |
| Agriculture and horticulture | 0.2 | 0.1 | 0.1 | 0 | 0.1 | 0.1 | 0.1 | |
| Industry | 15.3 | 9.7 | 5.9 | 5.6 | 3.3 | 3.3 | 3.2 | |
| Energy supply 2) | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | |
| Construction | 0.4 | 0.4 | 0.3 | 0.3 | 0.1 | 0.0 | 0.0 | |
| Waste disposal | . | . | . | . | 0.2 | 0.2 | 0.2 | |
| TSG and other target sectors | 3.5 | 3.7 | 3.5 | 3.7 | 3.7 | 3.7 | 3.7 | |
| Total gross discharge | 33.2 | 28 | 24.3 | 24.5 | 22.9 | 23.3 | 23.2 | |
| of which | urban wastewater treatment plants | 12.4 | 16.5 | 18.4 | 20.8 | 21.8 | 22.3 | 22.3 |
| national waters, fresh, direct discharge | 4.4 | 2.2 | 1.1 | 1 | 0.5 | 0.4 | 0.3 | |
| national waters, marine, direct discharge | 0.7 | 0.2 | 0.2 | 0.1 | 0.1 | 0.1 | 0.0 | |
| national waters through facilities managed by the water control authorities | 3.7 | 3.6 | 1.7 | 0.5 | 0.2 | 0.0 | 0.0 | |
| other surface water | 12 | 5.5 | 2.9 | 2.1 | 0.4 | 0.4 | 0.4 | |
| Discharge of effluent | 3.9 | 4.3 | 4 | 5 | 3.6 | 3.4 | 3.1 | |
| Load on the surface water 3) | 24.8 | 15.8 | 9.9 | 8.7 | 4.7 | 4.3 | 4.0 | |
| Source: CBS. | CBS/EDC/May03 | |||||||
| 1) One inhabitant equivalent (i.e.) is the quantity of substances for which the oxygen consumption in aerobic degradation equals that of the wastewater of one inhabitant per day. Calculation based on COD + N Kjeldahl; based on 180 g oxygen consumption up to 1986 and on 136 g from 1986. 2) Including water companies. 3) Total gross discharge minus discharges to UWWTPs plus discharge of effluent. | ||||||||
Developments
Most wastewater is treated in urban wastewater treatment plants. Only a small proportion is still discharged into surface water. The fall in the total pollution load by business, and particularly industry, has been achieved through increases in treatment capacity and by changes to the production processes.
Note
Oxygen-demanding substances are all organic and inorganic pollutants found in wastewater that take oxygen from water as they are broken down. Excess discharges of these substances can seriously disrupt the oxygenation conditions of the surface water, leading to, for example, fish deaths. The amount of oxygen-demanding substances is usually stated in inhabitant equivalents. An inhabitant equivalent corresponds to the oxygen demand of the pollutants in the wastewater that are discharged on average per day per person.
The table provides a complete overview of the discharges of all companies and households into sewers and surface water. The figures are based on the pollution units (inhabitant equivalents) established by water authorities for the imposition of the pollution levy.
References
- CBS (2003). Statline. Waterkwaliteitsbeheer. Zuivering van afvalwater, 1998. Statistics Netherlands, Voorburg/Heerlen.
Relevant sections and indicators in the Environmental Data Compendium
- Actors in the water chain
- Discharges into water and burden on surface water in the Netherlands, 1990, 1995, 1999 and 2000
- Guide to Environmental theme of Eutrophication
Relevant information outside of the Environmental Data Compendium
- More information about the discharge of oxygen-demanding substances and the burden on surface water can be found on Statline (Statistics Netherlands).
