Discharge of oyxgen-demanding substances and load on surface water in the Netherlands, flowchart 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.
Note on flowchart
The transport difference is the difference between total discharge to urban wastewater treatment plants (UWWTPs), calculated on the basis of levies, and the actual amount of pollution measured in UWWTP influent. The major reason for the difference is the inflow of extra pollution to the sewer system through run-off water from hard surfaces. These pollutants are not included in the discharges from households and companies.
The pollution value (expressed as inhabitant equivalents) is the quantity of oxygen-demanding substances for which the oxygen demand in aerobic degradation equals that of the wastewater of one inhabitant per day.
A time series for the development of emissions of oxygen-demanding substances and burden on surface water is presented elsewhere.
