Project background: A necessary upgrade

The rwzi Zeist wastewater treatment plant, managed by Hoogheemraadschap De Stichtse Rijnlanden (HDSR), required a major renovation to comply with the European Water Framework Directive (KRW). Many components had reached the end of their lifecycle, making modernization essential to maintain operational efficiency and sustainability.

HDSR, together with Eliquo Water & Energy BV, Van Hattum en Blankevoort, and Turntoo, formed the design and build team for the project. As a team, they set out to embed circularity into the renovation, moving beyond compliance to actively reduce environmental impact through smarter material choices and reuse strategies.

To achieve this, the design and build team implemented a Multi-Criteria Analysis (MCA) to compare different design scenarios based on cost, feasibility, Circularity and environmental performance. A key metric in this evaluation was the Environmental Cost Indicator (MKI), which quantifies lifecycle environmental impact in monetary terms (€). While sustainability was a clear ambition, the challenge was to ensure that environmental considerations were not just principles, but measurable factors guiding every project phase. 

Challenge: turning circular intentions into actionable insights

Infrastructure projects typically prioritize cost, risk, and planning efficiency, making it difficult to quantify and integrate circularity and environmental benefits in decision-making. Although circular ambitions were well established at HDSR, environmental data was often fragmented or not comparable, making it challenging to weigh sustainability against traditional KPIs.

To ensure circularity was truly embedded, HDSR needed a structured, data-driven approach to integrate full lifecycle impact assessments into their decision-making. This required accounting for:

• Material extraction and production (A1–A3)
• Construction and installation (A4–A5)
• Operational use and maintenance (B1–B7)
• End-of-life deconstruction and waste processing (C1–C4)
• Reuse and recovery potential (D)

Without clear, structured data, circularity could become a theoretical concept rather than a practical, comparable metric. The challenge was to translate sustainability ambitions into real, data-driven decisions.

The added value of using Madaster over other platforms was its direct access to multiple trusted environmental data sources, such as the EPEA database. This allowed for more accurate and transparent lifecycle assessments, resulting in a clearer understanding of the final MKI. As a result, project stakeholders could not only trust the outcomes but also communicate them with confidence, turning complex data into meaningful, actionable insights. 

Solution: Structuring circularity in every project phase with Madaster

From the start, environmental impact and circularity played a key role in comparing and selecting the best design scenario. By integrating Madaster, the project team quantified and optimized environmental impact, ensuring sustainability was embedded throughout every phase of the renovation process.

Systemic choice phase

Following the tender phase, stakeholders collaborated closely within the construction team. Using Madaster’s MKI and circularity assessments, the new circular design was systematically compared to the original reference design. Madaster’s ability to perform this comparison early, without needing a complete IFC or detailed 3D model, provided a clear advantage. It empowered the team to embed sustainability and circular principles deeply into design and procurement processes from the start.

Preliminary design phase

To ensure concrete steps towards sustainability ambitions, the team performed detailed scenario analyses on high-impact components, such as large water tanks and pipe materials. This provided deeper insights into the environmental impact per component, guiding subsequent design choices.

Final design phase

In this final phase, actual supplier-specific EPD data was collected and integrated into Madaster, replacing theoretical estimates with real-world data. This allowed decisions to be made based on verified environmental footprints, validating previous choices, and ensuring consistency between detailed design and procurement strategies—maintaining circularity and sustainability throughout execution.

Close collaboration with Turntoo ensured that circularity principles were translated into actionable measures, firmly embedding sustainability into the project delivery.

Results: A circular and cost-effective infrastructure project

By integrating Madaster’s structured environmental insights and enabling real-time collaboration between all stakeholders, HDSR and its partners achieved substantial sustainability and financial benefits. Madaster allowed multiple parties to work within a single platform – connected to the owner’s account – making it possible to input data, run analyses, and make decisions based on one shared truth and language.

• 40% reduction in MKI during the System Design phase, demonstrating a significant decrease in environmental impact early in the process.
• 20% lower investment costs by prioritizing adaptive reuse over demolition during the system design phase. This was made possible through smarter material selection and reuse strategies that not only preserved existing structures but also considered future residual value, significantly lowering the total cost of ownership.
• 8-month shorter project timeline, driven by early data-informed decision-making, reduced need for rework, and greater alignment between design, procurement, and execution teams.