On January 1, 2025, the new Directive 2024/3019/EU on Urban Wastewater Treatment (hereinafter the “Directive”) has entered into force.

In 2019, the European Commission had initiated an evaluation process that highlighted the effectiveness of existing urban wastewater regulations in (i) reducing water pollution and (ii) improving the treatment of water discharges over the past decades.

However, this evaluation also revealed the presence of high-impact pollution sources not yet sufficiently addressed by the current legislation, such as pollutants from small urban agglomerations and various harmful micropollutants. In parallel, the analysis showed that the urban wastewater sector is one of the largest energy consumers within the public sector.

The Commission has further linked the urban wastewater treatment sector to climate neutrality goals, recognizing its potential key role in reducing greenhouse gas emissions. In this sense, the objective of the Commission is to ensure that by 2045, urban wastewater treatment plants that handle loads of 10.000 population equivalents or more will use renewable energy generated on-site.

Proper regulation and correct treatment of wastewater are critical, since both domestic and industrial wastewater contain numerous organic and inorganic substances, oils, and other particles. Key pollutants include (i) nitrogen, (ii) phosphorus, (iii) organic materials, and (iv) micropollutants, primarily deriving from the cosmetic and pharmaceutical sectors.

The new Directive also covers small urban agglomerations, enhances treatment operations, and limits energy consumption and greenhouse gas emissions in the sector. More specifically, the new obligations focus on:

•  the application of the “polluter pays” principle;
• the monitoring and prevention of pandemics;
• the improvement of sanitation services.

The new legislative framework outlines a roadmap for the implementation of wastewater treatment obligations, divided by art. 2 into:

• primary treatment «by a physical or chemical process, or both, involving settlement of suspended solids, or other processes in which the BOD₅ of the incoming wastewater is reduced by at least 20 % before discharge and the total suspended solids of the incoming wastewater are reduced by at least 50 %»;
• secondary treatment «by a process generally involving biological treatment with a secondary settlement or another process which reduces biodegradable organic matter from urban wastewater»;
• tertiary treatment «by a process which reduces nitrogen or phosphorus, or both, in urban wastewater»;
• quaternary treatment «by a process which reduces a broad spectrum of micropollutants in urban wastewater».

To correctly understand the range of the new obligations, it must be underlined that the Directive imposes that Member States collect and treat wastewater from all agglomerations with over 1.000 population equivalents (1) (down from the threshold of 2.000 set forth by the previous legislative framework).

In addition, to combat pollution more effectively and prevent untreated discharges, art. 3 of the Directive requires that by 2035 Member States will be required to remove biodegradable organic matter from urban wastewater (the so-called “secondary treatment”) before its discharge into the environment. The Directive provides for exemptions only for Member States where sewer network coverage is very limited and would require investments that are excessively onerous, and for States that have joined the Union more recently and have just made significant investments to implement the new obligations (i.e., Croatia, Bulgaria, and Romania).

By 2039, the removal of nitrogen and phosphorus (the so-called “tertiary treatment”) will be mandatory for urban wastewater treatment plants that treat a load of 150.000 population equivalents or more. For the same plants, by 2045 Member States will be required to apply an additional treatment aimed at removing micropollutants (the so-called “quaternary treatment”).

These new obligations are aimed at preventing resource loss and promoting circular economy principles, such as recovering phosphorus from sludge for agricultural fertilizers.

(1) Legislative Decree 152/2006 (the Italian “Environmental Code”) defines an equivalent inhabitant as the biodegradable organic load with a five-day biochemical oxygen demand (BOD₅) of 60 grams of oxygen per day (Article 74, letter a).

Compared to the previous Directive 97/271/EC, which had a narrower scope, the new Directive adopts a more detailed and systematic approach to urban wastewater treatment, with greater involvement of Member States and more precise intervention measures.

The Directive’s objectives include (i) expanding coverage to more agglomerations and pollutants, (ii) achieving energy neutrality, and (iii) implementing extended producer responsibility.

In addition to the roadmap outlined under point 2, the Directive introduces new obligations with regards to:

• the implementation of collecting systems;
• extended producer responsibility;
• monitoring and risk assessment.

(a) On collecting systems

The Directive extends the obligation to establish sewage systems for all agglomerations over 1.000 population equivalents by 2035. Limited exemptions shall apply only where such systems are impractical or cost-ineffective, allowing for individual or appropriate systems that are alternative to the sewage ones.

Under art. 5, Member States must adopt integrated urban wastewater management plans by 2033 for agglomerations exceeding 100.000 population equivalents and by 2039 for high-risk agglomerations between 10.000 and 100.000. These plans should include preventive measures to keep unpolluted rainwater out of sewer systems.

(b) On extended producer responsibility

Art. 9 establishes that by December 31, 2028, Member States shall ensure that producers of pharmaceuticals for human use and cosmetic products – that are responsible for 92% of toxic micropollutants in wastewater – undertake the so called “extended responsibility”. They must cover at least 80% of the quaternary treatment costs, based on the toxicity and volume of their products.

This obligation reflects the “polluter pays” principle, holding those who cause environmental damage accountable. They are further required to undertake all necessary measures, including both prevention and remediation ones and the associated costs.

(c) On monitoring and risk assessment

Art. 17 requires Member States to establish national systems for cooperation and coordination of urban wastewater public health parameters by 2030.

Agglomerations exceeding 100.000 population equivalents must monitor antimicrobial resistance at treatment plant outlets.

Member States are further obliged to assess the environmental and health risks of urban wastewater discharges and, if necessary, implement additional measures that are beyond the Directive’s minimum requirements.

With specific reference to human health, urban wastewater can be analyzed to detect the presence of pathogens responsible for human diseases and pandemics. Indeed, the experience of the COVID-19 pandemic has demonstrated that wastewater monitoring can be a highly effective tool in predicting the future spread of potential viruses.

The Directive therefore requires Member States to carry out monitoring of certain health-relevant parameters in urban wastewater, including: the SARS-CoV-2 virus, poliovirus, influenza viruses, and other pathogens.

Like other recent European sustainability initiatives, the Directive aims to support climate goals and circular economy. Based on the new obligations, the wastewater sector will be required to reduce greenhouse gas emissions, currently representing around 0.85% of the EU’s total emissions.

With the goal of achieving energy self-sufficiency in urban wastewater treatment plants by 2045, the sector might be ready to meet the energy neutrality targets set by the EU initiatives.

Finally, considering the Directive’s goals, it is conceivable that the same will have positive impacts on environmental protection and urban wastewater management. This is further confirmed by the achievements of the previous regulations that have already significantly improved the quality of rivers, lakes, groundwater, and seas.