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Urban waste water treatment - outlook EEA

Indicator Specificationexpired Created 12 Apr 2007 Published 08 Jun 2009 Last modified 04 Sep 2015, 06:59 PM
This content has been archived on 12 Nov 2013, reason: Content not regularly updated
Indicator codes: Outlook 047
Required information is not filled in: Information about the starting date of the publishing schedule is missing.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

Wastewater from households and industry represents a significant pressure on the water environment because of the loads of organic matter and nutrients as well as hazardous substances. With high levels of the population in european countries living in urban agglomerations, a significant fraction of wastewater is collected by sewers connected to public wastewater treatment plants. The level of treatment before discharge and the sensitivity of the receiving waters determine the scale of impacts on aquatic ecosystems. The types of treatments and conformity with the directive are seen as proxy indicators for the level of purification and the potential improvement of the water environment.

Primary (mechanical) treatment removes part of the suspended solids, while secondary (biological) treatment uses aerobic or anaerobic micro-organisms to decompose most of the organic matter and retain some of the nutrients (around 20 - 30 %). Tertiary (advanced) treatment removes the organic matter even more efficiently. It generally includes phosphorus retention and in some cases nitrogen removal. Primary treatment alone removes no ammonium whereas secondary (biological) treatment removes around 75 %.

The indicator tracks the success of policies to reduce pollution from wastewater by describing the trends in the percentage of the population connected to public wastewater treatment plants with different levels of purification.

Scientific references

  • No rationale references available

Indicator definition

Definition: Percentage of population connected to primary, secondary and tertiary wastewater treatment plants. The indicator illustrates:
1. current level and future changes in level (accordingly UWWT directive)  of population connected to urban wastewater treatment (primary, secondary and tertiary);
2. current level and future changes (accordingly UWWT directive) of discharges of nitrogen and phosphorous from wastewater treatment plants

Model used: Water Model from EEA/ETC

Ownership: European Environment Agency

Temporal coverage: 2005, 2008-2015 (objectives of the UWWT directives)

Geographical coverage: EU 15 : Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden, United Kingdom; EU -5: Estonia, Hungary, Check Republic, Polamd, Slovenia,


1) Percentages of population connected to urban wastewater treatment;

2) Kg of nitrogen and phosphorous per inhabitant per year.

Policy context and targets

Context description

Global and Pan-European policy context

Indirectly the indicator can be useful within UN "Millennium Development Goals" and with the WSSD Plan of Implementation to ensure access to adequate drinking water and sanitation services.

EU policy context

The Urban Wastewater Treatment Directive (UWWT) prescribes the level of treatment required before discharge. It requires Member States to provide all agglomerations of more than 2 000 population equivalents (p.e.) with collecting systems. Secondary treatment (i.e. biological treatment) must be provided for all agglomerations of more than 2 000 p.e. discharging into fresh waters. Special requirements with intermediate deadlines depending on the sensitivity of the receiving waters are placed on agglomerations of more than 10 000 p.e. with various size classes of agglomerations. The performance of the treatment is assessed using 5 different determinands (BOD, COD, TSS, Ntot and Ptot). In the 15 Member States, there are about 20 000 agglomerations with more than 2 000 p.e., the population is 376 million inhabitants and the treatment capacity for the 8 181 agglomerations for which Member States provided detailed data is equivalent to organic matter from 469 million p.e.
For agglomerations smaller than described above and those equipped with a collecting system, the treatment must be appropriate, meaning that the discharge allows the receiving waters to meet the relevant quality objectives.
The WFD is asking for the estimation and identification of significant point and diffuse source pollution, in particular by substances listed in Annex VIII, from urban, industrial, agricultural and other installations and activities, based, inter alia, on information gathered under Articles 15 and 17 of Directive 91/271/EEC and other Directives. From the substances listed in the Annex VIII, the following are important for the indicator: substances which have an unfavourable influence on the oxygen balance (and can be measured using parameters such as BOD, COD, etc.), materials in suspension, and substances which contribute to eutrophication (in particular, nitrates and phosphates). Member States should thus take the necessary steps to build a data collection system able to provide these data, urban source being one of the sources listed. The ultimate aim of this is to reach the target of the WFD that is a good chemical and biological status for all waters in 2015, the discharge of substances being one of the major problems to face.

EECCA policy context

EECCA Environmental Strategy reveals main efforts in the region to improve quality of water and wastewater collcetion through more effective institutional and regulatory framework.


EU level

The Urban Waste Water Treatment Directive (UWWTD; 91/271/EEC) aims to protect the environment from the adverse effects of urban wastewater discharges. It prescribes the level of treatment required before dischargeand has to be fully implemented in the EU-15 countries by 2005 and in the ten new Member States by 2008 - 2015. The directive requires Member States to provide all agglomerations of more than 2 000 population equivalent (p.e.) with collecting systems and all wastewaters collected to be provided with appropriate treatment by 2005. Secondary treatment (i.e. biological treatment) must be provided for all agglomerations of more than 2 000 p.e. that discharge into fresh waters, while more advanced treatment (tertiary treatment) is required for discharges into sensitive areas. To help minimise pollution from various point sources, the Integrated Pollution Prevention and Control directive, which came into force 1996, has a set of common rules on permitting for industrial installations.
The achievements through the UWWTD and the IPPC directive have to be seen as an integrated part of objectives under the Water Framework Directive (WFD) which aim at a good chemical and biological status for all waters by 2015.

EECCA level

  • To increase wastewater collection and treatment in the long term


Links to other policies

UN 'Millenium Development Goals'

EECCA Environmental Strategy

Related policy documents

  • COM(2004) 248 final
    Implementation of Council Directive 91/271/EEC of 21 May 1991 concerning urban waste water treatment, as amended by Commission Directive 98/15/EC of 27 February 1998
  • Urban wastewater treatment summary report
    Summary report on: the identification of sensitive areas by the Member States; the measures implemented by the Member States with the view to the deadline of 31 December 1998; wastewater treatment in major cities; verification of the identification of sensitive areas by the Commission.
  • Water Framework Directive (WFD) 2000/60/EC
    Water Framework Directive (WFD) 2000/60/EC: Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy.


Methodology for indicator calculation

The methodology used consists of a simple techno-economic model developed by EEA European Topic Centre on Water in 2004, which links discharges of nutrients to population growth in areas connected to sewers and to developments in treatment technologies. The model covers most of the EU member countries and intends to reflect the level of nutrient discharges (i.e. nitrogen (N) and phosphorous (P)) after the urban waste water treatment directive (UWWT, 91/271/EEC) is fully implemented. The future waste water treatment in Cyprus and Malta is uncertain.

Calculating future waste water treatment and discharge from waste water treatment plants are based on information on:

Nutrientcapita: nutrient (N and P) load by waste water per capita and year

POP: population;

%POPconnectedWWT: percentage of population connected to sewers, and water has a retention percentage equal to zero.

A simple formula is used for calculations above:

Emissions= Nutrientcapita*POP*%POPconnectedWWT*(1-(%retention/100).

More detailed information can be available here.

Methodology for gap filling

For variables Nutrientcapita  and POP, there are relatively good estimates. Also good data is provided for the development in national populations. However, information in European coverage of waste water treatment (POPconnectedWWT) and the type of waste water treatment from some countries such as France, Latvia, Lithuania, and the Slovak Republic are missing and for some southern European countries there are no data later than 1995 (e.g. Spain and Italy). This data set has been supplemented with additional national information for some countries France (Ifen 2002); Italy (pers. comm. within the model); Ireland (EPA 2002).

Methodology references

No methodology references available.

Data specifications

EEA data references

  • No datasets have been specified here.

Data sources in latest figures


Methodology uncertainty

There is a lot of uncertainty about the actual implementation of the UWWT Directive in the individual countries. In the projections an assumption has been made that all agglomerations greater than 10000 p.e. discharging into sensitive areas will have tertiary treatment and other agglomerations greater than 2000 p.e. will have at least secondary. The category at least secondary treatment cannot be handled in quantitative projections so at least secondary treatment was set to secondary treatment. Coutnries may decide to have better treatment than required by the Directive. For countries with already high waste water treatment the future WWT was set to the current level of WWT, however, information in national and regional SoE reports indicate that they are still upgrading there WWT plants

There is an acknowledged important risk that the simplified calculations of future waste water treatment presented in the methodology might be in conflict with the more detailed national assessment.

Data sets uncertainty

First the current data and information on waste water treatment and population living in different sizes of agglomerations are limited. This makes it necessary to make assumptions with limited information available.

Secondly the information on the current level of waste water treatment is for some countries uncertain and inconsistent. The missing and uncertain data markedly reduce the number of countries for which the waste water treatment before and after can be compared with a sufficient confidence.

Rationale uncertainty

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata

Responsibility and ownership

EEA Contact Info

Anita Pirc Velkavrh


No owners.


Indicator code
Outlook 047
Version id: 1


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DPSIR: Response
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
European Environment Agency (EEA)
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