Rolling Revision of the WHO Guidelines for Drinking-Water Quality ...

Table 4.2 Municipal sewage sludge generated and disposed of in Europe in 1992
country amount disposal method (%)
(1000 t dw/y) agriculture landfilling incineration Other
Austria 170 18 35 34 13
Belgium 59.2 29 55 15 1
Denmark 170.3 54 20 24 2
Finland 150 25 75 0 0
France 865.4 58 27 15 0
Germany 2681.2 27 54 14 5
Greece 48.2 1) 10 90 0 0
Ireland 36.7 12 45 0 43
Italy 816 33 55 2 10
Luxembourg 8 12 88 0 0
Netherlands 335 26 51 3 20
Norway 95 56 44 0 0
Portugal 25 11 29 0 60
Spain 350 50 35 5 10
Sweden 200 40 60 0 0
Switzerland 270 45 30 25 0
UK 1107 44 8 7 41
TOTAL/AVG. 7387 36.4 41.6 10.9 11.1
1) other authors give 200 000 t dw/y
Source: Lindner, 1995
Pathogenic organisms and pollutants in wastes and sewage represent a significant
risk to the environment and human health (Siebe and Fischer, 1996). To protect the
environment and human health, national laws have been put in place to regulate the
re-use of sewage sludge. Certain criteria must be met before sewage sludge can safely
be re-used in, for example, land application for agricultural or landscaping purposes.
Governing bodies and environmental organisations (e.g. The Council of European
Communities, 1981, 1991; US EPA, 1993; Wilderer et al., 1996) mandate the
following measures:
• Limit values for heavy metals in soil, and in sewage sludge. Placement-related
assessments according to the pH or cation exchange capacity of the soils to
determine whether sewage sludge can be used without detrimental effects.
• The consideration of persistent organic pollutants.
• Limitation of the quantities of sewage sludge applied to farmland which, in
conjunction with limits for pollutants in sewage, would regulate the loading of
persistent organic pollutants and nutrients, such as nitrogen and phosphorus. Table
4.3 illustrates permissible amounts of sewage applied to agricultural land for
different countries.
• Prohibition of the application of sewage sludge to specific crops (for example,
grassland and vegetable crops) to prevent ingestion of pathogenic organisms and
pollutants through contaminated plants (Diez, 1994).
The origin of the sewage sludge is reflected in the proportion of pollutants to
nutrients. Sewage sludge originating from towns and cities may contain a greater
proportion of pollutants from industrial sewage than that originating from rural areas.
Nitrogen and phosphorus concentrations are less likely to be affected by the origin of