Urban waste water treatment

Indicator Assessment
Prod-ID: IND-15-en
Also known as: CSI 024 , WAT 005
expired Created 19 May 2005 Published 29 Nov 2005 Last modified 05 Oct 2017
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Wastewater treatment in all parts of Europe has improved significantly since the 1980s, however the percentage of the population connected to wastewater treatment in southern and eastern Europe and the Accession countries is relatively low.

Key messages

Wastewater treatment in all parts of Europe has improved significantly since the 1980s, however the percentage of the population connected to wastewater treatment in southern and eastern Europe and the Accession countries is relatively low.

How effective are policies aimed at improving urban waste water treatment at reducing discharges of nutrients and organic matter into surface waters?

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

Data source:

EEA-ETC/WTR based on Member States data reported to OECD/EUROSTAT Joint Questionare 2002

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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

Data source:

EUROSTAT Newcronos

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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

Data source:

EUROSTAT Newcronos

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Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (East)

Note: N/A

Data source:

EUROSTAT Newcronos

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Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (AC)

Note: N/A

Data source:

EUROSTAT Newcronos

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Changes in wastewater treatment in countries of Europe between 1980s and late 1990s (Southern)

Note: N/A

Data source:

EUROSTAT Newcronos

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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 levels of urban waste water treatment are applied in 'big cities' in the EU?

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

Data source:

DGENV 2004

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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

Data source:

DGENV 2004

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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

Indicator definition

The indicator on urban waste water treatment, CSI 024, collects data on the percentage of the population connected to sewage collection systems, as well as on the prevalence of primary, secondary and tertiary urban waste water treatment plants. The amount of urban waste water treated is expressed as population equivalents (p.e.). The indicator illustrates:

  1. the development of urban waste water collection and treatment in Europe since the 1970s;

  2. the development of more stringent urban waste water treatment practices;

  3. the level of urban waste water treatment in 'big cities' (agglomerations of > 150 000 p.e.) in the EU.

 

Units

The percentages of the population connected to primary, secondary and tertiary urban waste water treatment facilities.


Policy context and targets

Context description

The main objective of the UWWT Directive (91/271/EEC), and equivalent national legislation for non-EU countries, is to protect surface waters from the adverse effects of waste water discharges. The UWWT Directive prescribes the level of treatment required before discharge to surface waters. It requires Member States to provide all agglomerations of more than 2 000 p.e. with collecting systems. Primary (mechanical) and secondary (i.e. biological) treatments must be provided for all agglomerations of more than 2 000 p.e. that discharge 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 five different determinands (biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen  (Ntot) and total phosphorus (Ptot)).

For agglomerations smaller than those described above and equipped with a collecting system, the treatment must be 'appropriate', meaning that the discharge must allow the receiving waters to meet the relevant quality standards.

The UWWT Directive, adopted in 1991, is also a basic measure under the Water Framework Directive (WFD). The WFD requires the estimation and identification of significant point- and diffuse-source pollution, in particular by the substances listed in Annex VIII, from urban, industrial, agricultural and other installations and activities, based, inter alia, on information gathered, for instance, under Articles 15 and 17 of the UWWT Directive. Based on the substances listed in Annex VIII WFD, the following are important for this indicator:

  • substances that have an unfavourable influence on oxygen balance (and can be measured using parameters such as BOD, COD, etc.);
  • materials in suspension;
  • substances that contribute to eutrophication (in particular nitrates and phosphates).

Member States should thus take the necessary steps to collect these data. Reducing pollutants stemming from waste water is one of the key challenges of reaching good ecological and good chemical status of surface waters, as required by the WFD.

Targets

The UWWT Directive (91/271/EEC) aims to protect the environment from the adverse effects of urban waste water discharges. It prescribes the level of treatment required before discharge and should have been fully implemented in the EU-15 countries by 2005. For the newer Member States (i.e. the EU-13), staged transition periods were set within the Accession Treaties which, in principle, did not extend beyond 2015. However, in Romania, smaller agglomerations (with less than 10 000 p.e.) should comply with the directive by the end of 2018, and Croatia has different transition periods, from 2018 to 2023.

Under the directive, EU-15 Member States were required to provide all agglomerations of more than 2 000 p.e. with collecting systems and all waste waters collected had 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.


The achievements resulting from the UWWT Directive should be seen as an integral part of achieving good status for all waters under the WFD. 

 

        

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
  • Council Directive (91/271/EEC) of 21 May 1991
    Council Directive of 21 May 1991 concerning urban waste water treatment (91/271/EEC)
  • 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

Methodology for indicator calculation

The indicator is based on data from Eurostat, which are then aggregated into groups of countries. Percentages connected to each treatment type, weighted by total population in each country, were obtained from Eurostat tables. Compared with previous versions of the indicator, the time steps have been made consistent and the number of countries reported in each region in Figure 1 has been kept constant across the period.

A p.e. of 1 is equivalent to an organic biodegradable load having a 5-day BOD of 60 g per day.

'Big cities' is a term used in the UWWT Directive to identify cities of at least 150 000 p.e. or agglomerations responsible for large waste water discharges.

Methodology for gap filling

Gap filling was undertaken on the basis that once an urban waste water infrastructure had been put in place, it was likely to be used in subsequent years. Therefore, any gaps were filled with data from the most recent year reported, e.g. 2004 data carried forward to 2005. This approach was used for up to 9 years of gap filling, e.g. 2004 data could be carried forward to up to 2013.

 

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

For the assessment shown in Figure 1, countries have been grouped to show the relative contribution on a larger statistical basis. To provide a complete and comparable data set over the period, some countries have been omitted from the European overview.

Regional results are biased towards countries with the largest population (e.g. Turkey constitutes about 70 % of the inhabitants of the entire south-eastern Europe region).

 

Data sets uncertainty

Data reported to Eurostat sometimes provide an incomplete picture of inhabitants connected to waste water treatment (e.g. the percentage of the population connected to urban waste water systems is given, but the percentage for which the waste water is collected without treatment is missing).

Slovakia reported much of its urban waste water treatment as 'not specified', which is likely to lead to an underestimate of the percentage of treated waste water in that country.

 

 

Rationale uncertainty

Data gained from the UWWT Directive focuses on the performance of the treatment plant alone. However, urban waste water treatment systems could also include sewer networks with storm water overflows and storage, which are complex and therefore overall performance is difficult to assess. In addition to the treatments covered by the UWWT Directive, there are other possible treatments, mostly industrial, but also independent treatments of smaller settlements outside urban agglomerations not included in UWWT Directive reporting. Compliance with the levels defined in the directive therefore does not guarantee that there is no pollution due to urban waste water.

In addition, urban waste water treatment (primary, secondary or tertiary, as described above) is the main waste water treatment used across the EEA area, but there are other possible treatments classified as 'Other Waste Water Treatment', which are mostly industrial or independent treatments. Furthermore, there are differences in how countries have interpreted and implemented the UWWT Directive, leading to differences in the data reported. In particular, there are variations in the definitions of different classes of treatment between countries (classes based on performance or design capacity and tertiary treatment for nitrogen, phosphorus or organic matter) that, in turn, lead to differences in the level of purification attributed by the countries to the different classes. These differences emphasise the problem of using types of treatment plant as a proxy for the level of purification.

 

 

Data sources

Generic metadata

Topics:

information.png Tags:
,
DPSIR: Response
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 024
  • WAT 005

Contacts and ownership

EEA Contact Info

Caroline Whalley

EEA Management Plan

2010 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled every 2 years
Filed under: ,
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100