La quatrième étape d’épuration des eaux usées (en anglais)

Within the fourth purification stage, various processes for removing trace substances may be employed, including: activated carbon adsorption, ozonation and membrane filtration. These processes provide an additional treatment barrier before treated wastewater is discharged, helping reduce the release of micropollutants into receiving waters.

Changes to the EU Wastewater Directive

The revised EU Urban Wastewater Treatment Directive, effective January 2025, explicitly mandates “quaternary treatment for large plants and sensitive catchments,” with phased deadlines through 2045.

Mandatory introduction of this purification stage by December 31, 2035 is required for all sewage treatment plants with a capacity of 100,000 population equivalents (PE) or more in the EU. Smaller plants with a capacity of 10,000 to 100,000 PE are to implement this by 2040, provided that higher micropollutant concentrations pose a risk. Another goal is for sewage treatment plants to be operated in an energy- and climate-neutral manner by 2040, which includes regular energy audits and the use of renewable energies.

The Directive also extended manufacturer responsibility, whereby manufacturers of pharmaceuticals and cosmetic products are to contribute to the costs of implementing the fourth purification stage.

Significance For Municipal Sewage Treatment Plants

The new regulations pose several challenges for municipal sewage treatment plants, including:

• Financial burden: The introduction of the fourth stage of treatment requires significant investment in new technology and infrastructure.
• Technical adaptations: Treatment plants must expand or modernize their existing systems to accommodate the new processes.
• Operation and maintenance: The operation and maintenance of the new systems require additional expertise and training for staff.

A Risk-Based Targeting Approach

As wastewater treatment plants (WWTPs) seek to implement policies and procedures for compliance, avoiding universal mandates while targeting high‑impact sites first for technology or process upgrades will speed up potential outcomes through a risk-based approach.

Switzerland, which began implementation of a fourth treatment stage as early as 2016, has adopted a catchment‑risk approach to compliance, prioritizing plants upstream of drinking water abstraction points and ecologically sensitive water bodies. This approach may be worthwhile for facilities seeking to adapt their treatment to these new requirements.

Improving Treatment Plant Effectiveness

Implementing a fourth purification stage adds new processes to an already complex treatment environment. Effective flow measurement, water quality monitoring, data management and automation can help operators maintain visibility and control as they integrate these additional treatment processes.

To support these evolving treatment needs, Badger Meter offers a variety of products and solutions designed to improve the efficiency and effectiveness of wastewater treatment operations, including applications within the fourth purification stage.

Flow Meters

Precise flow meters are essential for monitoring and controlling water volume and flow measurement in treatment plants. These devices can be used in different areas of the plant to optimize water consumption and support efficient operation of treatment processes.

Ultrasonic flow meters are ideal for use in areas where high measurement accuracy is required, such as dosing chemicals in the fourth treatment stage.

Electromagnetic flow meters are particularly robust and suitable for use in harsh environments, making them ideal for use in all areas of the treatment plant.

Water Quality Monitoring Systems

Monitoring water quality is crucial for compliance with the new regulations. Advanced water quality monitoring systems that provide data in real time allow for immediate response to changes in effluent quality, limiting the potential for fines and pollution events to occur.

In-situ sensors that monitor parameters such as organic compounds, turbidity, pH and other important indicators can be used at different stages of wastewater treatment to maximize the efficiency of the treatment processes.

Online monitoring systems enable continuous monitoring of water quality and immediate detection of deviations from expected reads. These systems are particularly useful for monitoring the efficiency of the fourth treatment stage and adjusting operating parameters in real time.

Data Analysis and Management Solutions

Processing and analyzing large amounts of data is critical for optimizing operations in wastewater treatment plants. Comprehensive data collection and analysis solutions help operators make informed decisions.

Data management platforms collect and analyze data from various sources within the wastewater treatment plant. They provide detailed insights into the performance of the various treatment processes and help operators identify trends and improve efficiency.

Analytics software tools allow operators to analyze the collected data in detail and generate reports required to comply with the new regulations. They also assist in optimizing chemical dosing and controlling the aeration systems within the plant for further efficiency gains.

Automation Solutions

Automation of varied processes within wastewater treatment is an important factor in the efficiency and sustainability of these facilities.

As treatment plants add fourth-stage treatment processes, automated systems can help operators control and monitor the various processes within the wastewater treatment plant. These systems can be programmed to respond to real-time data and adjust operating parameters accordingly to maximize efficiency, maintain consistent performance and minimize energy consumption.

Remote monitoring capabilities allow operators to monitor and control the wastewater treatment plant remotely. This is particularly useful for quickly responding to unexpected events, identifying process deviations and continuously optimizing operations.

Preparing for Fourth-Stage Treatment

By using these advanced products and solutions from Badger Meter, wastewater treatment plants can efficiently implement the new requirements of the fourth stage of treatment while reducing their operating costs and minimizing environmental impact.