At the end of 2024, the EU Wastewater Treatment Directive (UWWTD) was adopted by the European Parliament. The directive was published as EU Directive 2024/3019 in the Official Journal of the European Union and represents a revision of EC Directive 91/271/EEC on urban waste water treatment, which was adopted in 1991. With the amended Wastewater Directive, the EU is setting new requirements for authorities and municipal wastewater management for the first time in over 30 years.
The directive came into force on January 1, 2025, and must be transposed into national law by July 31, 2027, in accordance with Article 33 (1). In this respect, the reporting obligations under the new EU Urban Waste Water Directive will apply from August 1, 2027. The reporting obligations under the EC Urban Waste Water Directive (91/271/EEC) will be repealed on that date in accordance with Article 32 (1), 2024/3019.
The switch to reporting in accordance with EU Urban Wastewater Treatment Directive 2024/3019 will significantly increase reporting requirements. This will also lead to a significant increase in the amount of data required. In order to ensure the availability of the relevant information and data, new processes and responsibilities must be established to ensure the timely delivery of data to data-holding agencies. To this end, it is first necessary to specify the data requirements and clarify the availability of relevant data. Where the quality or scope of the available data is insufficient, appropriate data collection processes must be developed.
The amended EU Urban Waste Water Directive 2024/3019 imposes a wide range of additional requirements on authorities and stakeholders in the water management sector. Key changes in the EU Urban Waste Water Directive 2024/3019 include requirements relating to the fourth treatment stage and, associated with this, requirements for the continuous monitoring of micropollutants. In this context, a risk assessment is planned to identify areas where the concentration or accumulation of micropollutants from municipal wastewater treatment plants poses an unacceptable risk to the environment or human health. Based on this assessment, a list of areas at risk is to be drawn up by the end of 2030, which will then be reviewed in 2033 and every six years thereafter and updated if necessary. In addition, the EU Commission has the power to adapt the methods used by member states for monitoring and evaluating micropollutants to scientific and technical progress by means of delegated acts.
Quaternary treatment with a minimum pollutant removal rate of 80% for dry weather runoff is to be introduced in stages by 2045, initially for wastewater treatment plants with a wastewater load of ≥ 150,000 PE, as well as for wastewater treatment plants in urban areas with ≥ 10,000 PE that discharge their wastewater into areas identified as vulnerable in the risk assessment. Regardless of the area into which a wastewater treatment plant discharges, monitoring for micropollutants must be implemented for all wastewater treatment plants with ≥ 10,000 PE.
In order to verify compliance with the required 80% purification effect, Annex I, Part C of the EU Urban Waste Water Directive specifies indicator substances to be used to determine the elimination rate of a wastewater treatment plant for micropollutants. The EU Urban Waste Water Directive 2024/3019 stipulates that the percentage of micropollutants removed must be determined for at least six substances in dry weather runoff. The substances are divided into two categories, with the number of substances selected from category 1 having to be twice as high as the number of substances selected from category 2 (see Table 1). If fewer than six substances can be measured in sufficient concentration, the competent authority shall, if necessary, designate other substances for the calculation of the minimum percentage of pollutant removal. To assess whether the required specific minimum percentage of pollutant removal of 80% has been achieved, the average of the percentages estimated for the removal of all the individual substances is applied. For the sampling of micropollutants, flow-proportional 24-hour or time-proportional 48-hour samples shall be taken at specified points at the outlet and inlet of the municipal wastewater treatment plant.
With its concept of testing the treatment effect using 12 indicator substances, as specified in the EU Urban Waste Water Treatment Directive, the directive relates directly to the concept specified in Swiss legislation, which has already proven itself in practical implementation (Wunderlin et al. 2024).
Table 1: Micropollutants to determine the elimination rate of a waste water treatment plant
Substance | CAS Number | Category |
Amisulprid | 71675-85-9 | Category 1 |
Carbamazepin | 298-46-4 | Category 1 |
Citalopram | 59729-33-8 | Category 1 |
Clarithromycin | 81103-11-9 | Category 1 |
15307-86-5 | Category 1 | |
Hydrochlorothiazid | 58-93-5 | Category 1 |
Metoprolol | 37350-58-6 | Category 1 |
Venlafaxin | 93413-69-5 | Category 1 |
Benzotriazol | 95-14-7 | Category 2 |
Candesartan | 139481-59-7 | Category 2 |
Irbesartan | 138402-11-6 | Category 2 |
4-Methylbenzotriazol | 29878-31-7 | Category 2 |
5-Methylbenzotriazol | 136-85-6 | Category 2 |