Wastewater treatment

A major cause of water pollution

If not properly treated, wastewater can be a major cause of water pollution, which impacts human health and the environment.

Water quality in the EU has improved enormously in the past 30 years, not least thanks to EU legislation on the treatment of urban wastewater, yet there is still too much pollution, with new pollutants emerging all the time. This pollution must be tackled in order to protect human health and the environment.

The EU’s goal is to achieve a zero-pollution environment by 2050. To this end, the Council has adopted updated rules on urban wastewater treatment, which date back to 1991.

Main pollutants

Originating from households or industry, wastewater carries a range of organic and inorganic substances, oils and other particles. Some of the most significant pollutants are nitrogen, phosphorus, organic materials and micropollutants.

Nitrogen and phosphorus

When you eat, you may cause nitrogen pollution.

Nitrogen and phosphorus are used as fertilisers in food production, and also in other sectors as additives, for example, or in the pharmaceuticals industry.

Organic materials

When you use the toilet, you may generate higher biological oxygen demand.

Oxygen is needed to decompose organic matter. The more organic matter there is in water, the greater the oxygen demand – which means not enough oxygen left for animals such as fish.

Micropollutants and microplastics

If you use cosmetics or medicines, you may create micro-pollutants.

92% of toxic micro-pollutants found in EU wastewater comes from pharmaceuticals such as antibiotics and cosmetics.

Nitrogen and phosphorus are the main nutrients in wastewater. Excessive levels of these chemical substances in rivers, lakes or seas promote the rapid growth of algae and aquatic plants, which can deplete oxygen levels when they die and decompose. This oxygen depletion harms fish and other aquatic organisms, a process called eutrophication.

Positive impact of EU wastewater treatment rules

30 years of EU wastewater legislation have proven successful. Over the years, the application of EU rules has greatly contributed to making rivers, lakes, groundwater and seas cleaner.

According to the 2019 evaluation of the EU legislation carried out by the Commission, the EU’s wastewater collection and treatment rate is almost 100%, and over 90% of it is treated in accordance with the high standards envisaged in EU rules.

As a result, the level of pollutants in treated wastewater has decreased enormously.

Decrease in main pollutants in treated wastewater

Clear downward trends can also be seen in the level of pollutants in EU rivers and groundwater.

Lower level of pollutants in rivers and groundwater

New rules on urban wastewater treatment

Three decades have passed since the rules on wastewater treatment were first adopted. New pollutants exist today and new opportunities have arisen to make water treatment energy-efficient and to better use data.

In October 2022, the European Commission presented a proposal to update the urban wastewater treatment directive (Council directive 91/271/EEC, later amended in 1998 as Commission directive 98/15/EC). The proposal was based on an evaluation of the rules concluded in 2019, which highlighted the tangible results the directive had helped to achieve and also the remaining challenges.

• Urban wastewater treatment directive (1998)

The 27 member states agreed on their position within the Council (‘general approach’) in October 2023. The European Parliament adopted its position in the same month. In January 2024, the Council's and the European Parliament’s negotiators reached a provisional political agreement on the proposal. The Council adopted the rules in November 2024.

• Urban wastewater: Council adopts new rules for more efficient treatment (press release, 5 November 2024)

The revised directive will:

• extend the rules to smaller towns
• further improve treatment operations 
• cut the sector’s energy use and greenhouse gas emissions
• make polluters pay
• help monitor and prevent pandemics
• improve sanitation, particularly for the most vulnerable individuals

Applying the new rules will require investment in the sector. However, water services are not expected to become more costly for individual households, and the long-term benefits for human health and the environment will far outweigh the costs that operators will incur.

Including smaller towns

43% of all EU urban agglomerations have fewer than 2 000 population equivalents (‘population equivalent’ is a measurement used to calculate urban wastewater pollution). Under the 1991 EU rules, these smaller towns do not have to collect and treat their wastewater, but nevertheless cause significant pollution in water bodies.

Under the new rules, all towns with a population of 1 000 people or more will need to abide by the wastewater treatment rules by 2035. This includes:

• setting up urban wastewater collecting systems
• treating wastewater to remove biodegradable organic matter before discharging it into the environment

Some derogations apply to smaller agglomerations and those in the member states that joined the EU most recently.

Removing nitrogen and phosphorus

The new rules will require member states to remove nitrogen and phosphorus by 2039, by further treating wastewater in plants for 150 000 or more population equivalents. By 2045, EU countries will also have to remove micro-pollutants.  

In addition, EU countries will need to better manage rainwater (in bigger cities only) to reduce emissions of organic matter and other pollutants. This will help more effectively deal with heavy rain, which has become more frequent due to climate change.

Contributing to climate goals and the circular economy

Under the new rules, the wastewater sector will need to reduce its greenhouse gas emissions, which today account for roughly 0.85% of all EU emissions.

The sector should achieve energy neutrality, which means that by 2045, urban wastewater treatment plants will have to produce the energy they consume. This energy can be produced on- or off-site, and up to 35% of energy can be purchased from external sources.

The new rules will also help avoid the loss of resources and favour their re-use into a circular model. For instance, phosphorus from sludge will be recovered and re-used to make fertilisers for crop production. 

Making industry pay

Over 90% of micro-pollutants found in wastewater are caused by pharmaceuticals and cosmetics.

Treatments to remove toxic substances in these sectors are available and effective. The new rules will require producers and importers to apply such treatments by introducing extended producer responsibility, based on the principle that the ‘polluter pays’.

Monitoring pandemics

Viruses and pandemics could be better prevented by monitoring wastewater.

Urban wastewater can be analysed to track the presence of pathogens responsible for human diseases and pandemics. The experience of COVID-19 has shown that monitoring wastewater can be a very effective means of predicting the future spread of a virus.

The new directive makes it a requirement for EU countries to monitor certain health parameters in urban wastewater. This includes the SARS-CoV-2 virus, polio, influenza viruses and other pathogens.

Improving sanitation

According to Eurostat, around 10 million people in the EU do not have access to basic sanitation facilities.

The new rules will require member states to ensure sanitation services, especially for the most marginalised and vulnerable people in the EU. Access to public toilets for all will also have to be improved.