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<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

A sensitive area must be identified if the body of water falls into one of the following groups:

  • Natural fresh-water lakes, other fresh-water bodies, estuaries and costal waters which are found to be eutrophic or may become eutrophic.
  • Surface fresh-waster intended for the abstraction of drinking water which contain more the concentration of nitrate laid down in the Councilīs nitrate Directive 75/440.
  • Any other area where further treatment is necessary to fulfill the purpose of the directive.

A less sensitive area is:

  • A marine body of water if the discharge does not adversely affect the environment provided that there is no risk that the discharged load may be transferred to adjacent areas.
  • Open bays, estuaries and other costal waters with a good water exchange and not subject to eutrophication or oxygen depletion or not likely to be so.

Figure 6.8 shows the sensitive and the less sensitive areas which have been identified by the Member States as of 1998, and Tables 6.13 and 6.14, respectively, indicate the removal rates for BOD5, nitrogen and phosphorous.

Figure 6.8: Sensitive and less sensitive areas

Table 6.13: Requirements for discharges into normal areas (values for concentration or for percentage reduction)

Minimum percentage
Reference method of measurement
BOD5, without nitrification
40 in high mountain
Addition on a
nitrification inhibitor
COD 125 75 Potassium dichromate
Total SS
60 in high mountain regions and 2000 to 10000 pe
90 in high mountain regions and 2000 to 10000 pe
Filtering through 0,45 um filter membrane
Centrifuging at least 5 minutes at mean acceleration of 2800 to 3200
Source: EEC, 1991


Table 6.14: Additional requirements for discharges into sensitive areas (one or both parameters may be applied depending on the local situation)

Minimum percentage
Reference method of measurement
Total phosphorus
2 mg/l P (10000 to
100000 pe)
1 mg/l P (more than
Molecular adsorption
Total nitrogen* 15 mg/l N (10000 to
100000 pe)
10 mg/l N (more than
70-80 Molecular adsorption
*The sum of total Kjeldahl-nitrogen.
Source: EEC, 1991

The European Commission is responsible to monitor and report upon the implementation of Directive 91/271. A first report was due in June 1994 but has been published in 1998 only due to delays in national reporting (CEE 1998). The report includes information on implementation as of July 1998, viz. coverage attained and projections concerning with wastewater collection systems and treatment plants, meeting the obligation concerning industrial waste discharge respectively via urban collection systems and treatment plants and by direct discharge into receiving waters, quantity and methods of disposal of sewage sludge, and projected investment needed to meet the requirement both with respect to collection systems and treatment plants up to the year 2005.

Additional up-to-date information is contained in the report on Environment in the European Union at the turn of the Century (EEA 1999). The report states that after implementation of the Directive, the population not connected to sewers will be halved compared to the present situation; around 30 million persons or 5% of the total waste water will not be connected to sewers (see Table 6.15 and Figure 6.9). It has been assumed that no untreated wastewater will be discharged. The majority will either be treated by secondary treatment or secondary treatment plus nutrient removal. In Spain, Italy, Portugal and the United Kingdom the majority of wastewater will receive secondary treatment, while in Germany, France, Greece, Luxembourg, The Netherlands, and Finland the wastewater will also be treated in plants with nutrient removal. In the countries with no specific information on treatment after implementation of the UWWT Directive more than 80% in Sweden and Denmark today receive treatment with nutrient removal and only small changes due to the Directive can be foreseen. In Austria it is assumed that secondary treatment plus nutrient removal will be provided whereas in Belgium and Ireland there will be at least secondary treatment.

Table 6.15: Wastewater treatment of the combined load from household and indirect industrial discharges in EU10* countries (in pe as of end 1994)

Rural population 5.7 0.4 13 2.5 3 0.003 0.2 1.3 1.1 2 29.2 5%


0 0 0 0 0 0 0 0 0 0 0 0
Primary 0 10.2 3 0.1 4.2 0.03 0 2.1 0 11 30.6 6%
Secondary 2.5 70.3 6 1.3 87 0.1 0.2 10.9 0 55 233.3 44%
P+S+nutrient removal 121 4.2 54.5 8.6 10.6 0.48 24 1.2 5.5 13 243.1 45%


123.5 84.7 63.5 10 101.8 0.61 24.2 14.2 5.5 79 536.2 100%
* EU10 countries include Germany (DE), Spain (ES), France (FR), Greece (GR), Italy (IT), Luxembourg (LU), Netherlands (NL), Portugal (OT), Finland (FI), and the UK (UK). Source: EEA, 1999

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