Urban waste water treatment
How effective are existing policies in reducing loading discharges of nutrients and organic matter?
Changes in wastewater treatment in regions of Europe between 1980s and late 1990s
Note: Only countries with data from all periods included, the number of countries in parentheses
EEA-ETC/WTR based on Member States data reported to OECD/EUROSTAT Joint Questionare 2002
Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (Nordic)
Note: Only countries with data at least for one year reported here
Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (Western)
Note: Only countries with data at least for one year reported here
Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (East)
Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (AC)
Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (Southern)
Over the past twenty years, marked changes have occurred in the proportion of the population connected to wastewater treatment and in the technology involved. Implementation of the Urban Waste Water Treatment (UWWT) Directive has largely influenced this trend. Decreases in discharges in eastern Europe (new Member States) and the Accession Countries are due to economic recession resulting in a decline in polluting manufacturing industries.
Most of the population in the Nordic countries are connected to wastewater treatment plants with the highest levels of tertiary treatment, which efficiently removes nutrients (phosphorus or nitrogen or both) and organic matter. More than half of the wastewater in central European countries receives tertiary treatment. Only around half of the population in southern and eastern countries and the Accession countries is currently connected to any wastewater treatment plants and 30 to 40 % to secondary or tertiary treatment. This is because policies to reduce eutrophication and improve bathing water quality were implemented earlier in the Nordic and central than in the southern, eastern and Accession countries.
A comparison with indicators CSI 19 and CSI 20 shows that these changes in treatment have improved surface water quality, including bathing water quality, with a decrease in the concentrations of orthophosphates, total ammonium and organic matter over the past ten years. Member States have made considerable investments to achieve these improvements but most of them are however late in implementing the UWWT Directive or have interpreted it differently and in ways that differ from the Commission's view.
What is the level of the Urban Waste Water Treatment Directive (91/271/ECC) implementation in large cities of the EU Member States?
Number of EU-15 agglomerations of more than 150 000 p.e. by treatment level, situation on 1st January 2002
Note: 169 of the 526 cities with population equivalent more than 150 000 did not have a sufficient standard of treatment on 1st of January 2002 to meet the objectives of the UWWT Directive
Percentage of total load in sensitive area, and percentage of load in sensitive area by country, not conforming to the requirements of the urban waste water treatment directive, 2001
Note: DE and NL have designated their whole territory as a sensitive area, but are not in conformity with the goal of 75% reduction of N
Only two EU Member States, Denmark and Austria, were close to conforming to the requirements of the UWWT Directive regarding their large agglomerations discharging into sensitive areas by the end of 2001. Germany and the Netherlands have designated their whole territory as a sensitive area, but are not in conformity with the goal of 75% reduction of nitrogen. 158 of the 526 cities with population equivalents greater than 150 000 did not have a sufficient standard of treatment by the end of 2001 to meet the objectives of the UWWT Directive.
The UWWT Directive requires Member States to identify water bodies as sensitive areas according, for example, to the risk of eutrophication occurring. Wastewater treatment facilities with tertiary treatment had to be available in all agglomerations with a population equivalent greater than 10 000 discharging into a sensitive area by 31 December 1998.
For large cities with population equivalents greater than 150 000, Member States were required to provide more advanced (than secondary) treatment by 31 December 1998 when discharging into sensitive areas, and at least secondary treatment by 31 December 2000 for those discharging into 'normal' waters. However, on 1 January 2002, 158 of the 526 cities with population equivalents greater than 150 000 did not have a sufficient standard of treatment, of which 67 in normal areas, 91 in sensitive areas and with a lack of reporting data for 11. Moreover 25 agglomerations had no treatment at all, including Milan, Cork, Barcelona and Brighton. The situation has since improved, partly due to more comprehensive reporting to the Commission, partly to real improvements in treatment; some of the cities made the necessary investment during 1999-2002, others plan to complete work soon.
An additional threat to the environment comes from the disposal of the sewage sludge produced in the treatment plants. The increase in the proportion of the population connected to wastewater treatment, as well as in the level of treatment, leads to an increase in the quantities of sewage sludge. This has to be disposed of, mainly by spreading on soils, to landfills or by incineration. These disposal routes can transfer pollution from water to soil or air and should be taken into account in other relevant policy implementation processes.
Indicator specification and metadata
Percentage of population connected to primary, secondary and tertiary wastewater treatment plants. The indicator illustrates:
1. changes in wastewater treatment in the regions of Europe since the 1980s;
2. conformity (in terms of providing tertiary treatment) by Member States with the requirement to provide, by 31 December 1998, stringent treatment for agglomerations with population equivalent (p.e.) more than 10 000 that discharge into sensitive areas;
3. levels of urban wastewater treatment in large cities in the EU (agglomerations >150 000 p.e.).
Percentages of population connected to primary, secondary and tertiary wastewater treatment.
Policy context and targets
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 EU Member States, there are about 25 000 agglomerations with more than 2 000 p.e., the population is 501 million inhabitants and the overall generated load of 621 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.
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.
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.
Methodology for indicator calculation
Eurostat data are used and aggregated in groups of countries. Average of percentages connected to each treatment type, weighted by total population in each country:
National resident population = "WW0_1 National resident population" if available or else "Table: pjan, unit: inhabitant, Population by sex and age on 1. January of each year"
% of population connected to a type of treatment for one area = sum of (National resident population X "WW0_2_1 Urban waste water treatment of primary treatment"or
"WW0_2_2 Urban waste water treatment of secondary treatment" or
"WW0_2_3 Urban waste water treatment of tertiary treatment") or
"WW0 5: Urban wastewater collecting system without treatment"
EU aggregated and national data are used as presented on DG Environment's web page and reports.
EU aggregated values representing the type of treatment applied in the wastewater treatment plants of 586 big cities/big dischargers (250,2 mil. p.e.) reported in 2011 by the Member States and Norway were retrieved from the latest version of Waterbase via a series of subsequent queries linking information on agglomerations with total generated load higher than 150 000 p.e., treatment plants serving those agglomerations and the information on the percentage of total generated load treated in particular treatment plants. First, the sequence of scripts retrieved disaggregated information at the big city/big discharger level. Disaggregated information was then aggregated at the national level.
Methodology for gap filling
For the Eurostat dataset, gap fillings were made, by using figures provided by the respective NFPs during the review process or by replacing data available in Newcronos.
No methodology references available.
For the assessment shown in Figure 1, countries have been grouped to show the relative contribution on a larger statistical basis and to overcome the incomplete nature of the data. Complete dataset (ie data available for all years ad all countries) is not available for either of the geographic groups except for South-eastern countries (since the beginning of 2000 ies). Aggregated values are calculated only for the years for which the most complete dataset (with regard to number of responding countries) is available.
Data sets uncertainty
Data gained from the UWWTD focuses on the performance of the treatment plant alone. But wastewater treatment systems could also include sewer networks with storm water overflows and storages which are complex and whose overall performance is difficult to assess. In addition to the treatments covered by the UWWTD there are other possible treatments, mostly industrial, but also independent treatments of smaller settlements outside urban agglomerations not included in UWWTD reporting. Compliance with the levels defined in the directive therefore does not guarantee that there is no pollution due to urban wastewater.
In addition Urban Waste Water Treatment is the main waste water treatment used across the EEA area, but there are other possible treatments that are treatment in Other Waste Water Treatment, mostly industrial, or in independent treatments. Furthermore there are differences in how countries have interpreted and implemented the Directive leading to differences in the data reported. There are especially variations in the definitions of different classes of treatment between countries (classes based on performance or on design capacity and tertiary treatment for N, P or organic matter) that in turn lead to differences in the level of purification attributed by the countries to the classes. These differences all the more emphasize the problem of using types of treatment plant as a proxy for the level of purification. Member States have also been taken to court by the European Commission because of insufficient application of the Directive.
Waterbase - UWWTD: Urban Waste Water Treatment Directive
provided by Directorate-General for Environment (DG ENV)
Water statistics (Eurostat)
provided by Statistical Office of the European Union (Eurostat)
6th Commission Summary on the Implementation of the Urban Waste Water Treatment
provided by Directorate-General for Environment (DG ENV)
Water (Primary topic)
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
- CSI 024
- WAT 005
Contacts and ownership
EEA Contact InfoPeter Kristensen
EEA Management Plan2010 (note: EEA internal system)
Frequency of updates
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe’s environment.
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