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Indicator Assessment
The treatment of urban waste water is fundamental to ensuring public health and environmental protection. Urban waste water treatment in all parts of Europe has improved over recent decades.
The proportion of the population connected to waste water treatment plants in northern countries has been above 80 % since 1995, with more than 70 % of urban waste water receiving tertiary treatment.
In central European countries, connection rates have increased since 1995 and are now at 97 %, with about 75 % receiving tertiary treatment.
The proportion of the population connected to urban waste water treatment in southern, south-eastern and eastern Europe is generally lower than in other parts of Europe, but has increased over the last 10 years with levels now at about 70 %.
The treatment of urban waste water from our homes and workplaces is fundamental to ensuring public health and environmental quality. The main objective of the Urban Waste Water Treatment (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, such as organic pollution, the associated development of bacteria and fungi, and oxygen depletion, which degrade aquatic life. This is achieved through the collection and treatment of waste water in settlements and areas of economic activity (agglomerations) with a population equivalent (p.e.) of more than 2 000. In most cases, the UWWT Directive stipulates that waste water must be subject to biological treatment (secondary treatment), but in catchments with particularly sensitive waters, such as those suffering from eutrophication, more stringent tertiary waste water treatment may be required to substantially reduce nitrogen and phosphorus pollution.
The installation of waste water treatment facilities first requires the set-up of a sewage collection system and then the provision of facilities to treat the collected waste water. Where there is a low proportion of a population connected to waste water treatment facilities, it may be due to a lack of financial resources (or priority) for providing the sanitation services or to a high proportion of the population living outside agglomerations. In the latter case, where people live in scattered communities, individual sanitation systems may be the most feasible solution. Such systems may provide treatment efficiencies that are similar to those of larger urban waste water treatment plants.
The indicators used in this assessment to measure discharged loads of organic matter and nutrients from urban waste water treatment plants to European surface waters are:
Compared with earlier versions of this indicator, some changes in historical data have been included owing to corrections made by countries in the Eurostat data set.
The percentage of the national population connected to urban waste water treatment facilities
In central European countries, there was a high overall urban waste water treatment connection rate, of 97 % (Austria, Belgium, Denmark, Germany, Luxembourg, Netherlands, Switzerland and United Kingdom) in 2015 (Figure 1). The rate is slightly lower in northern countries, at 86 % (Finland, Iceland, Norway and Sweden).
The connection rates in eastern, southern and south-eastern countries are similar:
Notes:
1. These statistics are influenced by countries with high numbers of inhabitants; for example, Sweden and Poland account for about half of the total population of the northern and eastern regions, respectively, while Turkey represents about 70 % of the total population of the south-eastern region.
2. There are some countries for which data are reported in Figures 2-8 that are not represented in Figure 1, owing to there being gaps of more than 9 years in the reported data.
2. The percentage of the national population connected to tertiary urban waste water treatment facilities
More than 77 % of the population of northern and central Europe is connected to an urban waste water treatment plant that implements tertiary treatment, preventing significant amounts of nutrients and organic matter from reaching surface waters. Waste water generated by more than half of the population in southern and by over 60 % of the population in eastern Europe receives tertiary treatment. In central and southern countries, this percentage increased between 1995 and 2015 (from 47 % to 80 % in central Europe, and from 15 % to 53 % in southern Europe), while for eastern countries the percentage increased from 36 % to 61% between 2005 and 2015. In south-eastern Europe, the percentage of the population connected to treatment plants with tertiary treatment is lower, at about 20 % (an increase from 7 % in 2005), with 23 % of the population in this region being connected to secondary treatment.
The timetable for the compliance with the UWWT Directive varies. For the EU-15 (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden and the UK), the latest date to fully comply with the directive was 31 December 2005. For the newer Member States (i.e. the EU-13) in central and eastern Europe and in the Mediterranean, staged transition periods have been set within the Accession Treaties. In principle, these transition periods 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. Croatia, as the newest EU Member State, has different transition periods, from 2018 to 2023.
Northern Europe (Figure 2): the connection rate is between about 80 and 90 % in Finland, Iceland, Norway and Sweden. In the cases of Finland and Sweden, treatment is almost entirely at the tertiary level. In Norway, about 20 % of connected urban waste water receives primary treatment only, while in Iceland the majority of the collected urban waste water either receives primary treatment only or is not treated. The trends in the rate of the national population connected to urban waste water treatment plants appear stable, with slight increases in the proportion receiving tertiary treatment in Norway being the main change in recent years.
Central Europe (Figure 3): countries in central Europe have some of the highest overall connection rates in Europe — more than 90 % of the population connected in all countries other than Ireland. The proportion of the population connected to tertiary treatment ranges from 80 to 99 % in Austria, Denmark, Germany, the Netherlands and Switzerland. Tertiary treatment connection rates among this group of countries were lowest for Ireland (18 % of the population connected to tertiary treatment).
Southern Europe (Figure 4): the overall percentage of the population connected to urban waste water treatment ranges from 30 to 99 %. The rate is above 90 % in Greece, Malta and Spain. Tertiary treatment is most prevalent in Greece (89 %), followed by France and Spain, with 60-70 % of the urban waste water receiving this high level of treatment. There was a significant upgrade in treatment facilities in these countries between 2005 and 2010. In Cyprus, Malta and Portugal, the percentage of the population connected to tertiary treatment is below 20 %. Moreover, Portugal reported that over 10 % of the population is connected to collecting systems without treatment.
Eastern Europe (Figure 5): the overall proportion of the population connected to urban waste water treatment ranged from 70 to 85 % (with the exception of Slovakia) in 2015. Over 70 % of the population in the Czech Republic and Estonia is connected to tertiary treatment, while Hungary, Lithuania and Poland reported a tertiary treatment connection rate of 59-65 %. In Latvia, the rate of connection to tertiary treatment is lower, at about 17 %, and in Slovenia, about 27 % of the population is connected to tertiary treatment. Slovakia reported that 65% of the population was connected to urban waste water collecting and treatment systems in 2015.
South-eastern Europe (Figure 6): the percentage of the population connected to urban waste water treatment plants ranges from 48 to 87 %. In Bulgaria and Romania, about half of the treatment is tertiary, while in Croatia and Turkey primary or secondary treatment prevails. Just under a quarter of the population of Turkey is connected to collecting systems without treatment, but there has been steady progress in treatment availability and the level of treatment since 1995. While there was a significant increase in treatment availability in Croatia between 2005 and 2012, there has been limited progress in connecting populations to wastewater treatment in Bulgaria and Romania since 2005.
Western Balkans (Figure 7): where it is collected in the Western Balkans, urban waste water is mainly collected without treatment. The overall percentage of the population connected to urban waste water treatment plants ranges from 35 to 59 %, although most of this urban waste water is not treated. In Albania, all the waste water collected receives some level of treatment, with about half receiving tertiary treatment.
Figure 8 summarises the type of treatment applied in the urban waste water treatment plants of large cities in 2013 or 2014. Of the total generated load of larger cities, 75.4 % is treated to remove nitrogen and/or phosphorus. A considerable proportion, namely 21.4 % of the total load, receives secondary treatment, while 0.9 % of the total load of all large cities receives only primary treatment.
The indicator on urban waste water treatment, WAT005, 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 from 'big cities' is expressed as population equivalents (p.e.).
The indicator illustrates:
The percentages of the population connected to primary, secondary and tertiary urban waste water treatment facilities (Figures 1 and 2).
The percentage of population equivalent (p.e.) was used for “big city” treatment (Figure 3).
The main objective of the Urban Waste Water Treatment Directive (91/271/EEC) (UWWTD), and equivalent national legislation for non-EU countries, is to protect surface waters from the adverse effects of waste water discharges. The UWWTD prescribes the level of treatment required before discharge to surface waters. It requires Member States to provide all urban settlements (called 'agglomerations' in the UWWTD) 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 urban settlements of more than 10 000 p.e., with various size classes. The performance of the treatment is assessed using several determinands (biochemical oxygen demand (BOD) and chemical oxygen demand (COD); plus total nitrogen and total phosphorus in the case of more stringent treatment).
For urban settlements 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 UWWTD, 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 UWWTD. Based on the substances listed in Annex VIII WFD, the following are important for this indicator:
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.
Collecting and treating waste water has required huge investment across Europe in recent decades. The kinds of new challenges facing urban waste water treatment, such as climate change, resource efficiency and improved environmental protection, are set out in the EEA briefing Urban waste water treatment for 21st century challenges.
Further information on emissions from industry to water, including to urban waste water treatment plants, is available in Industrial waste water treatment - pressures on Europe's environment.
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 have complied 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 urban settlements 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 urban settlements 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 UWWTD should be seen as an integral part of achieving good status for all waters under the WFD.
The indicator is based on data from Eurostat, which show the percentage of the population connected to each treatment type. Compared with previous versions of the indicator, Figure 1 now shows the treatment level in EEA member and cooperating countries in 2017, rather than grouping countries according to region.
A p.e. of 1 is equivalent to an organic biodegradable load having a 5-day BOD of 60 g per day.
Tertiary treatment is known in the UWWT Directive as 'treatment more stringent than secondary' and includes the application of secondary treatment.
'Big cities' is a term used in the UWWT Directive for cities of at least 150 000 p.e. or agglomerations responsible for large waste water discharges. Countries themselves identify their 'big cities'.
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. 2016 data carried forward to 2017. This approach was used for up to 5 years of gap filling, i.e. 2012 data could be carried forward to up to 2017.
The main uncertainties relate to data reported to Eurostat. In 2005, treatment for 24 % of the population was 'unknown', which fell to 15 % in 2017. The second area of uncertainty relates to numbers of inhabitants, as these do not necessarily align with reported population data, though error here is generally small.
The 'EU-27' value is strongly influenced by the situation in Member States with large populations (France, Germany, Italy and Spain).
At country level, the population figure and the generated p.e. load are not usually the same, as there can be other sources of organic pollution, such as food industry and temporal changes in population owing e.g. to tourism.
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).
'Big cities' data sometimes include data from agglomerations that are much smaller than 150 000 p.e. However, the impact of such errors on the final percentages is rather small.
Data from the UWWT Directive focuses on the performance of the treatment plant and of the agglomeration. 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 the definitions of different classes of treatment (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.
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/urban-waste-water-treatment/urban-waste-water-treatment-assessment-4 or scan the QR code.
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