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Management of micropollutants: implications of the new EU wastewater directive

In recent decades, the increase in urbanization and industrialization has raised growing concerns about micropollutants in wastewater. These compounds, ranging from pharmaceuticals to industrial chemicals, can be a threat to human and environmental health. As our understanding of their impact deepens, there is an urgent need to research and effectively address their presence in wastewater, thus ensuring the protection of aquatic ecosystems and public health.

In this regard, the new Urban Wastewater Treatment Directive marks a milestone with several key aspects regarding micropollutants: the requirement of quaternary treatment, Extended Producer Responsibility (EPR), and energy neutrality goals introduce a new phase in wastewater management that will address this type of pollution, while also posing significant challenges for the sector.

The current Urban Wastewater Treatment Directive (91/271/EEC), in force since 1991, has significantly improved the quality of water bodies in Europe. However, recognizing the need to further reduce the pollution load discharged into the environment, to align the directive with the European Green Deal, and the new challenges in urban wastewater treatment, as well as governance aspects such as EPR, the European Commission has proposed a revised directive. This revision has followed the usual legislative process, with a trilogue phase between the European Commission, Parliament, and Council, and an agreement reached last January between the European Parliament and Council on the Commission's proposal. On April 10th, the European Parliament approved the text of the new legislation, now pending formal approval by the European Council before publication and entry into force.

Quaternary treatment, Extended Producer Responsibility (EPR), and energy neutrality introduce a new era in wastewater management

One of the novel aspects of the proposed new directive is the treatment requirements for the removal of micropollutants, i.e., substances present in very low concentrations. Specifically, the new directive defines a micropollutant as "a substance as defined in Article 3(1) of Regulation (EC) No 1907/2006 of the European Parliament and of the Council, including its breakdown products, that is usually present in the aquatic environment, urban wastewater and/or sludge and which can be considered hazardous to human health or the environment based on the relevant criteria set out in Part 3 and Part 4 of Annex I to Regulation (EC) No 1272/2008 even in low concentrations.”

To achieve this, the new directive proposes their removal through quaternary treatment in Article 8, mandatory for wastewater treatment plants treating a load ≥ 150,000 population equivalents (p.e.), as well as treatment plants treating a load of more than 10,000 p.e. if there is a risk of micropollutant accumulation in the aquatic environment, according to a gradual implementation schedule with 100% of discharges subject to treatment by December 31, 2045. A minimum percentage of removal of 80% of six substances used as indicators of the operation of the quaternary treatment is required, out of 13 substances listed in Annex I, Table 3, belonging to two categories:

Category 1 (substances that can be very easily treated):

  • (i) Amisulprid (CAS No 71675-85-9),
  • (ii) Carbamazepine (CAS No 298-46-4),
  • (iii) Citalopram (CAS No 59729-33-8),
  • (iv) Clarithromycin (CAS No 81103-11-9),
  • (v) Diclofenac (CAS No 15307-86-5),
  • (vi) Hydrochlorothiazide (CAS No 58-93-5),
  • (vii) Metoprolol (CAS No 37350-58-6),
  • (viii) Venlafaxine (CAS No 93413-69-5);

Category 2 (substances that can be easily disposed of):

  • (i) Benzotriazole (CAS No 95-14-7),
  • (ii) Candesartan (CAS No 139481-59-7),
  • (iii) Irbesartan (CAS No 138402-11-6),
  • (iv) Mixture of 4-methylbenzotriazole (CAS No 29878-31-7) and 5-methylbenzotriazole (CAS No 136-85-6).

Additionally, the new directive introduces the "polluter pays" principle with Extended Producer Responsibility (EPR). This is a novel mechanism in the water sector but already used in the waste sector for packaging, for example. The producer of a product that causes environmental damage, which then needs to be disposed of or recycled, must pay for the amount of product they place on the market, and that money would be used to finance recycling, or in this case, the costs of removal through quaternary treatment.

According to the Commission, the pharmaceuticals and cosmetics sectors are jointly responsible for up to 92% of the toxic load in wastewater, so these sectors will have to finance the installation of quaternary treatments, in addition to their operating and monitoring costs. This is a controversial issue as these sectors believe that other sectors are also responsible, while the Commission has said that in the long term, it will assess whether other sectors can be added to the EPR scheme. These producers must cover at least 80% of the costs, according to Article 9; however, those who demonstrate that the quantity of the substances contained in the products they place on the EU market is below 1 tonne per year, that are substances rapidly biodegradable in wastewater, or that they do not generate micropollutants in wastewater at the end of their life, are exonerated.

What about PFAS and microplastics?

The new directive acknowledges that PFAS are found in urban wastewater, sometimes at high concentrations: “It is therefore essential to better understand the pathways of PFAS into the environment and to monitor them in the inlet and outlet of the urban wastewater treatment plants.” Article 21 establishes monitoring requirements at the inlets and outlets of urban wastewater treatment plants. Among those requirements, and in the case of agglomerations of 10,000 p.e. and above, monitoring would include microplastics, as well as PFAS – the latter as part of the parameters in Part B of Annex III to Directive 2020/2184 on water intended for human consumption, in cases where wastewater is discharged in catchment areas for drinking water abstraction.

The new directive acknowledges that PFAS are found in urban wastewater, sometimes at high concentrations

Article 21 also refers to the procedure by which the Commission will establish a methodology for measuring the parameters "PFAS Total" and "Sum of PFAS" in urban wastewater, no later than 2 years after the entry into force of the directive.

Moreover, Article 21 refers to monitoring the presence of microplastics both in wastewater and in sludge, particularly when reused in agriculture, in the case of urban agglomerations of more than 10,000 p.e. In this case as well, the text refers to the procedure by which the Commission will establish a methodology for measuring the presence of microplastics in wastewater and in sludge, no later than 2 and a half years after the entry into force of the directive.

The Commission must carry out an evaluation of the new directive by December 2033 and by December 2040 (Article 30), which includes an analysis of the feasibility and appropriateness of the development of an EPR system for products that generate PFAS and microplastics in urban wastewater, based on the monitoring data from Article 21 on PFAS and microplastics at the inlets and outlets of urban wastewater treatment plants.

Challenges for water utilities

The challenges for the wastewater treatment sector in relation to micropollutants do not only involve the implementation of quaternary treatments, but also that these will increase the energy cost of treatment, whereas the revised directive sets an energy neutrality objective. Specifically, Article 11 establishes that at national level 100% of wastewater treatment plants treating ≥ 10,000 p.e. must be energy self-sufficient by December 31, 2045, following a gradual implementation schedule, and without including the purchase of renewable energy. Energy audits will be required by December 31, 2028, for wastewater treatment plants treating ≥ 100,000 p.e. and the collecting systems connected to them, and by December 31, 2032, for wastewater treatment plants treating a load between 10,000 and 100,000 p.e. and their collecting systems.

The new directive will entail business opportunities for developing new quaternary treatment technologies, as well as drive the implementation of technologies to reduce energy consumption and greenhouse gas emissions in wastewater treatment plants.

However, significant investment needs are anticipated for new treatment and monitoring requirements and to achieve the energy neutrality objective, although reducing energy consumption will be cost-effective in the long term. This is where the new EPR scheme will be a game changer in terms of financing the requirements for removal of micropollutants under the new directive.