Beggen Wastewater Treatment Plant

A major capacity upgrade while maintaining operations – a complex challenge for GEPROLUX

The expansion of the Beggen wastewater treatment plant is a flagship strategic project for GEPROLUX in the realm of project management. This large-scale undertaking, defined by its extensive technical infrastructure, presents the unique challenge of integrating new facilities and systems within an existing operational site. Throughout the works, the continuous treatment of wastewater must be ensured. As a critical infrastructure, the plant is required to remain fully functional at every stage of the project.

Unlike construction on a greenfield site, which allows for linear planning, this project demands precise coordination and rigorous execution. The new structures must be seamlessly connected to the existing installations without disrupting their operation.

The objective is ambitious: the treatment capacity will more than double, increasing from 210,000 to 450,000 population equivalents. In addition, stricter environmental requirements impose tighter emission thresholds. A fourth treatment stage will also be introduced, incorporating ozone and activated carbon processes capable of removing micropollutants.

The complexity of the phasing, with its numerous stages and adjustments, calls for dynamic planning and constant anticipation. Much like solving a Rubik’s Cube, the final solution will only emerge after a series of precise and coordinated combinations.

Beggen: the convergence point for the region’s wastewater

The Beggen site was selected for topographical reasons: located at the lowest point in the municipality of Luxembourg, it offers optimal gravity-based collection of wastewater. Since 1920, the City has treated wastewater from its network here before discharging it into the Alzette. A second plant, formerly located in Bonnevoie, was replaced by a 6 km collector that now channels all wastewater to Beggen.

Today, the Beggen wastewater treatment plant is the largest in the country. It treats not only the wastewater of the capital, but also that of several neighbouring municipalities such as Strassen, Bertrange, Leudelange, Roedgen, as well as the western part of the airport.

In response to population growth and ongoing urbanisation, the City of Luxembourg has launched a major expansion of the plant. The goal is to increase its treatment capacity from 210,000 to 450,000 population equivalents by 2047. Completion of the works is scheduled for 2032.

The project includes the addition of a new primary sedimentation stage following the existing mechanical treatment, followed by biological treatment in nine SBR (Sequencing Batch Reactor) tanks, each with a capacity of nearly 10,000 m³. A fourth treatment stage will also be implemented, incorporating ozone and activated carbon processes to eliminate micropollutants and trace substances, in line with new environmental requirements.

In parallel, the sludge treatment line will be partially modernised. A new mechanical dewatering stage for the various sludge fractions (MSVE – mechanical dewatering of primary and biological sludge) will be introduced. Additionally, a third digester will be built, while the two existing digesters will undergo complete renovation.

These works aim to ensure the performance, resilience, and sustainability of this critical infrastructure, which is essential for environmental protection and public health.

Optimising the schedule: reducing timeframes, risks and costs

The expansion of the Beggen wastewater treatment plant represents a strategic mission for GEPROLUX, highlighting the complexity of managing a critical infrastructure project in a constrained environment. Ensuring the continuous operation of the plant—essential for public health and environmental safety—requires a high level of coordination, reliability and responsiveness.

The GEPROLUX team—comprising Eveline Beck, Christopher Simon, Carole Schmit and Pascal Meisberger—manages the day-to-day operations of the site from a temporary base installed on location. This constant presence enables direct supervision and swift adaptation to on-site realities.

From the earliest phases, GEPROLUX took charge of optimising the schedule in close collaboration with the various design partners. Through in-depth analysis and targeted coordination, several stages were able to be carried out in parallel, significantly reducing the overall duration of the works.

This approach also greatly limited the need for temporary installations, which always pose a risk to the proper functioning of the plant. By reducing their number and duration, operational safety was reinforced—an essential consideration for such a sensitive infrastructure.

Finally, this optimisation resulted in substantial savings for the project owner, by lowering costs associated with temporary measures and accelerating the implementation of permanent structures.

A bespoke wastewater treatment plant: complexity, continuity and innovation

The Beggen wastewater treatment plant has unique characteristics that directly influence the design and management of its expansion project. Due to the urban lifestyle in Luxembourg, wastewater volumes fluctuate significantly between day and night, requiring finely tuned treatment processes. This atypical dynamic calls for tailored technical solutions, integrated into an intelligent infrastructure capable of responding to real-time variations.

Service continuity is an absolute requirement throughout the works. Every intervention must be carefully planned to avoid any interruption to the water flow. This involves temporary diversions, targeted replacements, and precise coordination between the various trades. Every component of the network—be it a cable, pipe, or channel—plays a vital role, and any modification can have repercussions on the overall operation.

The first new installations, including the initial SBR tanks, were commissioned in 2024. To initiate the biological process, sludge was transported from several treatment plants across the country. The continuation of the works requires the demolition of the existing administrative building, which will be replaced by a new facility at the site entrance. This building will house the City of Luxembourg’s teams, and its completion is a prerequisite for the next phase of construction, particularly the remaining SBR tanks.

From summer 2025, the project enters a particularly technical and structural phase. Works will focus on the construction and equipping of the third digester, the development of the new administrative building, as well as the implementation of the primary sedimentation structure and the new mechanical sludge dewatering stage (MSVE).

At the same time, significant upgrades are planned for the electrical installations, including the renovation and modernisation of the medium and low voltage distribution networks. The construction of three additional SBR tanks, along with a technical building, will complete this phase.

Most of the structures must meet stringent watertightness requirements, adding complexity to the civil engineering design. Circular structures, such as digesters, present particular challenges in terms of formwork, reinforcement, and volume control, as they must simultaneously contain liquids and gases.

The biogas produced by the digesters will feed a cogeneration system designed to produce electricity and hot water, thereby contributing to the site’s energy efficiency.

Protecting the client: rigour, foresight and responsiveness

A project of this scale, carried out on infrastructure that remains continuously operational, inevitably involves technical and organisational challenges. The ability to manage these situations with precision and efficiency is essential to ensure safety, quality, and the achievement of the client’s objectives.

The GEPROLUX team plays a central role in this dynamic, ensuring coordination between design, permits, execution, and the various stakeholders. For example, during the construction of the cone for the new digester, complex operations were required, including a continuous 24-hour concrete pour using a negative formwork, demanding meticulous organisation and exceptional mobilisation of resources.

The commissioning of the first SBR tank also presented technical challenges, particularly due to failures in certain equipment. Thanks to comprehensive all-risk construction insurance and swift technical expertise, the affected components were replaced without significant impact on the overall schedule.

In all such situations, GEPROLUX’s priority remains the same: to safeguard the client’s interests by ensuring service continuity, installation safety, and strict adherence to timelines. This proactive and structured approach enables effective management of unforeseen events while maintaining a high level of reliability across the entire project.

The Team

Eveline Beck – Head of Project Management

With extensive experience in managing complex projects, Eveline Beck oversees the overall administrative follow-up of the operation. She is responsible for analysing consultancy bids, preparing budget forecasts, monitoring subsidies, managing contracts, and supporting strategic decision-making. She also participates in the permanent steering committee meetings. Although focused on administrative aspects, she remains closely connected to the field and regularly visits the construction site.

Christopher Simon – Project Manager

As the lead on-site coordinator, Christopher Simon is responsible for operational planning, daily monitoring of works, and coordination with the client. He structures management processes on the project platform and ensures consistency in technical decisions throughout the construction phase. His in-depth knowledge of the project makes him a key contact for all matters related to its history and the evolution of technical choices.

Carole Schmit – Project Manager

A civil engineer, Carole Schmit specialises in overseeing structural works. She is primarily involved on the Beggen site, where she coordinates between construction companies and design offices. Her deep understanding of materials and construction methods enables her to manage technical interfaces effectively. She plays a vital role in facilitating communication among the various project stakeholders.

Pascal Meisberger – Project Engineer

A process engineering specialist, Pascal Meisberger is mainly involved in the design, permitting, and procurement phases. He acts as a liaison between design offices and the client, ensures compliance of contractual documents, and leads technical discussions. He is also responsible for managing the project platform, ensuring smooth and structured information exchange among all parties involved.