First in Belgium: a DN 2000 sewer collector that can’t stop for a second is being rehabilitated with UV-cured GRP liners. The unique twist? They have to keep a whole city running with a bypass of 13,000 m³/h while crews worked just before the treatment plant. To show how that’s engineered, international experts were invited on site. Amongst them: IKT’s Ashwini Ausekar, who shares insights from her site visit.

Belgian sewer operator Aquafin and their contractor TM Kumpen – Willemen Infra hosted a site visit for project partners and international guests at the wastewater treatment plant RWZI in Bruges, Belgium. They witness first-hand the renovation of the major sewer collectors serving 238,500 residents. Massive collectors (diameters 1500–2000 mm) that transport wastewater from the city and surrounding area are being structurally renewed.

This remarkable rehabilitation covers a total length of 156 meters, installed with a pull-in method and cured using 36 kW UV lamps progressing at approximately 45 cm per minute. The GRP liners, supplied by Impreg, were transported to site with a total weight of 100 tons.

Why Renovation Was Urgent

Inspection revealed that the reinforced concrete host pipes, originally 19 cm thick, had in some places been reduced to as little as 2 cm due to severe corrosion caused by hydrogen sulfide (H₂S). In certain sections, reinforcement steel had already dissolved. Without intervention, the risk of sewer collapse and subsequent sinkholes would have been high, with major social, ecological, and economic consequences.

To guarantee continued wastewater transport during the works, a temporary bypass pumping system was installed, capable of diverting up to 13,000 m³/hour to the treatment plant. This ensured uninterrupted operations while rehabilitation proceeded in 60-hour continuous shifts.

A Project of Exceptional Complexity

Christa Coppens, Project Manager at Aquafin, highlighted the unique challenges:

• Long and large-diameter (1500–2000 mm) pressure pipelines at depths up to 9 meters
• Highly permeable and potentially contaminated soil
• Strong H₂S formation and severe pipe deterioration
• Need for sustainable execution with minimal disruption
• Requirement to maintain continuous wastewater treatment plant discharge

 

Optimized CIPP Solution

Given the complexity, Aquafin opted for a competitive procedure with negotiation rather than a traditional open tender. This approach enabled contractors to propose optimized solutions within defined boundaries, fostering collaboration, trust, and innovation.

Relining with Quality and Safety at the Forefront

According to Gert-Jan Merkx, General Manager at Kumpen, success depended on combining technical expertise with strict safety management. Deep excavations, manhole rehabilitations, and access shafts were managed under stringent safety rules, with all site visitors wearing helmets, safety shoes, and high-visibility vests during the tour.

Quality control was also a priority: samples were tested, installation software protocols were monitored, and additional sensors measured UV radiation, viscosity, and temperature development during curing.

Preventive Management Pays Off

Danny Baeten, Director of Project Management at Aquafin, emphasized the wider context:

“Every €1 invested in preventive management saves €3–5 in emergency repairs and damage. By renovating today, we safeguard public funds, protect past investments, and avoid costly surprises tomorrow.”

 

The Flemish sewer network, valued at over €10 billion, faces increasing pressure from aging infrastructure. Proactive projects such as Bruges demonstrate the importance of timely rehabilitation to avoid ecological damage, sinkholes, and untreated discharges into nature.

An International Exchange of Knowledge

The site visit at RWZI Brugge welcomed over 30 delegates, including participants from the Netherlands (Arnhem), Germany, and Belgium. The group toured the site in teams of six, observing preparations such as the installed preliner, protective foils, and manhole laminations. Installation of the impregnated GRP liner began the following day, with continuous work planned for 60 hours.

During the visit, Danny Verhulst from Aquafin kindly hosted the tour in English, for Ashwini Ausekar. We had engaging discussions on innovation in sewer rehabilitation, particularly regarding corrosion and acid attack in concrete pipes – an issue of growing relevance across world. His openness in sharing expertise and perspectives made the exchange especially valuable.

Ashwini Ausekar was very impressed: “This project is a milestone for trenchless rehabilitation in Europe. The combination of scale, innovative UV-cured GRP technology, and the collaborative procurement model sets a new benchmark for complex underground infrastructure works. I am grateful to Aquafin and TM Kumpen – Willemen Infra for the kind invitation and warm hospitality, and especially to Danny Baeten and Danny Verhulst for making the visit both insightful and inspiring.”

Contact Person

Ashwini Ausekar, M.Sc.
phone: +49 209 17806-0
email: ausekar@ikt.institute

 

Last week, the interim results of our international LinKa – Liner for Sewers research project were presented at the headquarters of the Water Services Association of Australia (WSAA) in Melbourne. The event brought together project partners from Australia and New Zealand in a hybrid workshop setting to discuss first findings and exchange expertise. Many Questions were asked, many answers were given.

LinKa – an international research project

With LinKa, we are investigating the performance limits of Cured-in-Place Pipe (CIPP) liner applications. CIPP is one of the most widely used trenchless rehabilitation methods for sewer systems worldwide. But how far can this method go when it comes to damaged or highly stressed pipes?

To answer this question, we have set up several 1:1 scale test rigs. These rigs replicate real-life sewer conditions and include a variety of predefined damage scenarios – such as cracks, fractures, or deformations. The scenarios were developed in close collaboration with a steering committee of public sewer network owners, ensuring that the research reflects practical challenges faced by operators.

Testing and evaluation

CIPP manufacturers have installed their liners in these full-scale test rigs. Our task is to evaluate the performance of the different CIPP liners employed under realistic conditions and to provide detailed reports to the participating sewer network owners. In this way, the project creates a transparent basis for evaluating liners and understanding their application limits.

A broad international network

LinKa is truly international in scope: 40 sewer network operators from Australia, Belgium, Germany, Ireland, the Isle of Man, the Netherlands, New Zealand, the States of Jersey and the United Kingdom are actively involved. This broad participation ensures that findings are relevant not only for one country, but for sewer operators worldwide.

Interim results in Melbourne

The interim results were recently presented by our colleagues Dr Iain Naismith and Ashwini Ausekar at WSAA in Melbourne. The hybrid workshop format allowed our partners from various Australia and New Zealand utilities to attend in person or online. The event sparked valuable discussions about the first findings and the next steps in the project.

Coordination in the Southern Hemisphere

In the Southern Hemisphere, the project is coordinated by WSAA, the national association of water suppliers and wastewater utilities in Australia. James Gardner, James Goode and Greg Ryan represented WSAA at the event. From our side, our Managing Director Roland W. Waniek joined the workshop in person.

Contact persons

• Iain Naismith, PhD
  phone: +44 7983 605219
  email: naismith@ikt.institute

 



Greg Ryan, Water Services Association of Australia (WSAA)

• Ashwini Ausekar, M.Sc.
  phone: +49 209 178060
  email: ausekar@ikt.institute

 

Settlement damage, uneven bedding, and poor re-excavation capability – these are common issues on sewer construction sites. Often, the cause lies in the backfill.

Temporarily Flowable Self-Compacting Backfill (TFSB) materials promise better performance – but which ones actually deliver?

We tested five different TFSB products in full-scale sewer trench simulations. The aim: to evaluate how these materials perform under realistic construction conditions.

The Approach: Large-Scale Testing, Real-Site Conditions

At the IKT’s large-scale test facility in Gelsenkirchen, we set up actual sewer construction scenarios, including pipes, manholes, trench shoring, and bedding layers.

We tested the materials for:

• Flowability and installation quality
• Walkability and early load-bearing capacity
• Re-excavatability after hardening
• Volume stability and risk of subsidence
• Environmental performance and recyclability

We used innovative inspection tools like the 🔗 MAC system for pipe-soil stiffness and a walkability test after 3 hours to assess real-life performance.

Key results for sewer construction:

• Not all flowable backfills are created equal: Some harden too much, while others remain unsuitable for overbuilding, e.g. for road construction, for up to 56 days.
• Re-excavation is a challenge – for good excavation, TSFB must not exceed a compressive strength of 0.3 N/mm² after 28 days.
• New test methods like the Mini-MAC and walkability test ensure practical and measurable evaluation.
• Environmental compliance, shrinkage, and recyclability vary widely between products.
• Two materials stood out: RSS® Flüssigboden and carbofill® showed the best balance between performance, usability, and long-term suitability.

Comparative Test Results: Two Materials Performed Best – Others Failed Key Criteria

We graded each material on a scale from 1.0 (“very good”) to 6.0 (“inadequate”).

Special emphasis was placed on re-excavation capability and early workability, both essential for practical use.

Top performers:
✅RSS® Flüssigboden – well-balanced, walkable, easy to re-excavate
✅ carbofill® – strong technical performance and consistent usability

We observed critical issues with:
❌ Terrapact© – hardened too much, impossible to excavate
❌ WBM-Flüssigboden® – excessive shrinkage, ammonia emissions, and safety concerns

Materials that failed key performance or environmental criteria were ruled out for sewer construction use.

 

Why This Matters for Sewer Network Owners and the Industry

Our study provides clear guidance for sewer network operators, planners, and contractors:
✔️ Backfill material can now be selected systematically and criteria-based
✔️ Supports long-term performance and maintainability
✔️ Promotes safer, more cost-effective, and more sustainable construction

Especially in urban environments, where tight schedules and complex infrastructures are the norm, choosing the right backfill is critical – not just technically, but also economically and environmentally.

Access the Full Study

The full paper is published in the journal:

Tunnelling and Underground Space Technology (Open Access)
Published: July 2025
Authors: Nicole Kimmling, Matteo Rubinato, Bert Bosseler et al.
🔗 Read the publication

🔗 Read also:
Liquid > Solid > Ready? Comparison of Five Flowable Backfills for Sewer Pipe Trenches

Acknowledgements

We would like to thank the members of the municipal steering committee for this project, who have closely accompanied our project and provided us with tremendous support.

The steering committee was composed of representatives from the cities:
Burscheid (Chair), Düsseldorf, Gladbeck, Hamm, Lünen, Mülheim, Oberhausen, Recklinghausen, Solingen, Troisdorf, Wuppertal

They also contributed to the financing of the project, as did the Ministry for the Environment, Nature Conservation and Transport of the State of North Rhine-Westphalia, Germany. We would like to express our sincere gratitude for this as well.

We would like to thank also the Cologne District Government, as well as Leibniz University of Hannover and Koblenz University of Applied Sciences for their support.

Contact

Prof. Dr.-Ing. habil. Bert Bosseler
E-Mail: bosseler@ikt.institute

Nicole Kimmling, M.Sc.
E-Mail: kimmling@ikt.institute

 

Last week, we hosted a truly inspiring international conference in Gelsenkirchen, Germany:

“AI, Drones, Sensors and Robots for Smart Sewers and Urban Drainage 2025”

More than 50 experts from across the globe gathered to explore how cutting-edge technologies are transforming the way we inspect and manage urban drainage systems.

Key topics and contributions

• AI-powered sewer diagnostics at Tokyo Metropolitan Sewerage
• Stormwater prediction through deep learning


International case studies from Tokyo, the UK, Germany, Canada, and more

• Real-time data from Water and Wastewater Networks for AI analysis
• Practical AI use cases by Yorkshire Water, United Utilities, and Gelsenwasser
• Drone and sensor applications from WinCan, Andrews.Engineer, and Wirtschaftsbetriebe Duisburg
• Robotic inspection and maintenance featuring the MAC System, Pipebots from the University of Sheffield, and even Robo-Dogs from Jade Hochschule
• Cleaning-driven asset management presented by Sewer Robotics

Conference Programme 2025:
https://bit.ly/IKT-International-Conference-2025

International networking

In the various sessions and inbetween, participants took part in vibrant discussions and networking, proving:

The challenges in urban drainage – aging infrastructure, climate resilience, workforce shortages – are global.

Smart technologies offer new opportunities for efficient, cost-effective solutions.

 

Live demonstrations

Live demonstrations featured drone flights, IKT’s MAC system for non-destructive assessment, and robotic dogs navigating sewer networks – all in IKT’s test facilities.

This conference was more than just an event – it was the start of deeper international collaboration in wastewater innovation. It marks the beginning of closer international cooperation in the field. The journey continues next year!

 

 

Read the excellent summary of our conference, which appeared in the renowned British trade journal ‘Drain Trader Magazine’: Pushing boundaries: reflections from the IKT conference

 

Take a look at the photo impressions of this lively conference here: https://bit.ly/Photos-Conference-2025

 

In the IKT research sewer pipe, Andrews Engineers from Canada demonstrate how they inspect sewers with their drone:

 

RoboDog visits the International Conference on Communications and Transportation (IKT) and his owner, Prof. Dr. Sebastian Hollermann, reports on the possibilities of using him in the sewer system:

 

This international conference brings together experts and innovators to explore cutting-edge AI, robotics, and sensor technologies for real-time monitoring, predictive maintenance, and smarter infrastructure solutions.

The future of urban drainage and sewer management is here!

Key topics for Smart Sewer Systems and Urban Drainage:

• AI – How digitalization can transform their management
• Drones and Robotics – Improving safety and cost-effectiveness
• Robotics – Automating maintenance for efficiency
• Sensor Technologies for Inspection & Real-Time Data – Enhancing decision-making
• Predictive Analytics – Preventing failures before they happen

Programme:
International Conference 2025: AI, Drones, Sensors and Robots for Smart Sewers and Urban Drainage
2 – 3 April 2025

Venue
IKT – Institute for Underground Infrastructure
Gelsenkirchen / Germany

Who should attend?
Municipalities, utilities, innovation teams, engineers, industry professionals, contractors and suppliers who are shaping the future of sewer systems and urban drainage!

For delegates: Registration

For exhibitors: Registration is open

Contacts

Ashwini Ausekar
Phone: +49 209 17806-0
E-Mail: ausekar@ikt.institute

Dr. Iain Naismith
Phone: +44 7983 605219
E-Mail: naismith@ikt.institute

Held to celebrate IKT – Institute for Underground Infrastructure’s 30th anniversary, on September 11th and 12th, 2024, in Gelsenkirchen, Germany, the event brought together IKT’s research collaborators with sewer and urban drainage network owners from around the world.

The value of providing face to face opportunities for international exchanges in experience to address common problems was the key takeaway from IKT’s recent, in person, “Sewers for the 21st Century II” International conference.

The feedback from guests confirmed the conference was a resounding success, fostering an environment of collaboration and knowledge exchange. With a focus on resilience, sustainability, and innovation in sewer and urban drainage systems, attendees left with new insights, strengthened personal networks, and a shared vision for the future.

Dr Iain Naismith, IKT

Iain Naismith, the conference organizer and moderator commented:

The event took place was exactly as planned – by providing an informative and relaxing environment for our guests to hear and exchange their ideas for solving issues they face with ageing infrastructure and climate change adaptation. There was with plenty of time and opportunity in the programme to get to know each other, develop new contacts and initiate future collaboration.

Day 1: International Perspectives on Sewerage Issues

Session I was planned as a series of short presentations on current issues from different countries, we initially heard how different regions are tackling the challenges of ageing sewer networks and urban drainage systems.

The event began with a warm welcome from IKT’s Managing Director, Roland W. Waniek, followed by an introduction from Dr Iain Naismith, Senior Research Fellow and International Project Manager at IKT.

The first session, centered on the key sewerage issues of the 21st century, highlighted diverse experiences from around the world.

• James Gardner, Water Services Association of Australia, opened the discussions with a presentation on environmental research innovations in Australia and New Zealand.
• Dr Ajit Salvi, Brihanmumbai Municipal Corporation, India, particularly focused on the issue of improving the health and safety of sewage workers.


Prof. Jean-Luc Bertrand-Krajewski, INSA, Lyon/France

• Prof. Jean-Luc Bertrand-Krajewski, INSA Lyon, France, used coping with the consequences of urban sprawl in the City of Lyon as a case study for issues in France.
• Wendy Franken, Vlario, Belgium, emphasized collaboration between sewer network owners on multi-year planning, implementing rainwater and drought plans, making space for water and budgeting. In her role as President of the EWA (European Water Association), she also highlighted addressing implementation of the revised Urban Wastewater Treatment Directive.
• Saskia Holthuijsen, Stitching Rioned, The Netherlands, highlighted additional issues including recruitment to the sector, digitalisation, circular economy and energy.


Tom Ogden, Yorkshire Water, UK

• Thomas Ogden, Yorkshire Water, United Kingdom, considered dealing with storm overflows, flooding and pollution and explained how collaborative research was addressing issues.
• Thomas Brueggemann, IKT, Germany explained how changes in climate, demographics, sustainability and technologies are affecting networks and how collaboration between municipalities was helping address some issues.

The session gave guests a broad view of how countries are working to future-proof their infrastructure.

 

In the afternoon IKT’s Scientific Director, Prof. Bert Bosseler, gave a vision of where IKT is heading in its research and knowledge sharing on risk-oriented asset management and rainfall management, before guests were given a conducted tour of new research facilities and current projects.

IKT has just taken over from the builders its new Materials Testing Laboratories, which have EU funding support for their construction, to enable us to stay ahead of the curve in testing the new materials and products being brought to market. Dieter Homann, Director of Materials Testing and his team demonstrated a range of new testing machines including impact testing, visual inspection and destructive testing.

The current research element of the tour comprised first a viewing of the Mini-MAC, a novel non-destructive inspection system for determining the structural stability of pipes and the pipe-soil system in smaller diameter pipes.

In the yard outside the laboratory guests viewed and discussed 1:1 scale test rig mock-ups and pipe damage scenarios for our current LinKa project examining the limits of performance of CIPP lining, end sealing and lateral connection repair of larger diameter pipes.

 

LinKa (‘Liners für Kanalisation’ (sewers)) and
Linka Partner Projects – International Collaboration

LinKa project examining the limits of performance of CIPP lining

This is a Euro 2.5m project examining the limits of performance of CIPP liners for the rehabilitation of larger diameter sewers. Funded by the Ministry of the Environment of North Rhine-Westphalia and a steering group of 10 municipalities, it has involved development of 1:1 scale test rigs with a variety of damage scenario into which CIPP (Cured In Place Pipe) liners will be installed and evaluated. Alongside this major German project, IKT is running Partner Projects with network owners from Ireland, UK, Isle of Man, States of Jersey, Belgium, The Netherlands, Australia and New Zealand, addressing specific issues with CIPP they have raised. A total of 40 networks owners are involved across the main project and partner projects.

Guests also viewed the IKT large test facility, an 18m x 6m x 6m floodable test chamber for 1:1 scale underground infrastructure evaluation. This is currently being prepared to host LinKa project test rigs to determine how complete CIPP systems (liner, manhole end seals and later connection repairs against groundwater pressure.

They also heard how IKT plans to develop its rainfall/urban drainage testing facilities with a new laboratory building for a large rainfall generating test rig and enhancement to the large test facility and flow rig capabilities. These are also supported by EU research infrastructure funding.

 

Guided tour of Zollverein Coal Mine

North Rhine-Westphalia has been grappling with sewer and urban drainage issues relating to its coal mining and industrial heritage and its impact on subsidence, topography and ground water levels.

It was therefore fitting that guests were treated to an evening guided tour of Zollverein Coal Mine Industrial Complex, a UNESCO World Heritage site, where they could hear about and see this history. This also tied in with a visit the next day to see new sewer pumping station facilities.

Day 1 finished with a Conference Dinner near the Zollverein Mine.

 

Day 2: Addressing Ageing Infrastructure and Innovation

The second day continued two sessions focusing on extending the life of ageing sewer infrastructure and new innovations.

• Maria Rus, City of Almere, The Netherlands, mentioned the outcome of field experiments on tree root barriers and pipe joint resistance, but focused on how Almere, the newest city in the Netherlands already has many issues with sewers and how they are working to improve things.
• Ilda Clos, SA Water, Australia, explained how SA Water is improving how it makes informed responses to new housing developments connecting to its network and how the state is addressing network infrastructure investment.


Francieli Thums and Valentin Kovachev, Wessex Water, UK

• Francieli Thums, Wessex Water, United Kingdom, presented a range of solutions that Wessex Water has adopted for optimising its sewer infiltration investigations and for sealing sewers against infiltration.
• Dr Iain Naismith, IKT, Germany, provided an overview of how the Emschergenossenschaft, the regional sewer network operator in the Emscher Catchment Area around IKT, has made a Euro 5 Billion investment over 15 years to install hundreds of kilometers of new foul sewer to disconnect it from surface run off. This was also an introduction to the afternoon visit to one of the Emschergenossenschaft’s very large pumping stations.

 

Innovation in Urban Drainage Technology

The final session of the conference emphasized innovation in urban drainage technology.

• Caroline Wadsworth, Isle Utilities, United Kingdom, inspired the audience by showing how innovations can move from concept to implementation.
• Aaroh Swarup, Indian Society for Trenchless Technology, discussed bold steps in subsurface markets in India.
• Prof. Simon Tait, University of Sheffield, United Kingdom introduced Pipebots, a cutting-edge technology that deploys autonomous robots for sewer inspection and repair.
• The session concluded with a presentation on the progress with the EU funded Co-UDlabs Project by Prof. Jean-Luc Bertrand-Krajewski, INSA Lyon, France, which is a collaborative community of seven urban drainage laboratories, including INSA, Sheffield University and IKT.

Consortium of Urban Drainage Laboratories

Across borders: research institutions from Europe network their laboratories.

“Co-UDlabs” is an EU Horizon Funded ‘start-up community’ of European research organisations that have urban drainage testing facilities.

This 4-year project has involved a large number of ‘Trans National Access’ projects where industry and academia have been using facilities in other countries to undertake research on solutions to climate change and ageing drainage assets.

IKT to take part in €4M Horizon 2020 project to build collaborative Urban Drainage research labs communities

Visit of Huge Pumping Station

To conclude the two days, guests were taken to see the Emschergenossenschaft’s very impressive Pumping Station in the Emscher Catchment with an 8-storey deep shaft and 12 pumps, with a lift of 25m.

Part of Emschergenossenschaft’s multi-billion-euro project, nicknamed the Ruhr Area’s “Sewer Autobahn”, which separated surface water from foul drainage, it served as an inspiring example of Germany’s forward-thinking approach to sustainable water management.

 

Takeaways – networking and collaboration: the highlights of the Conference

One of the most significant outcomes of the event was the enthusiasm participants expressed about networking. The conference provided ample opportunities for attendees to connect with peers, exchange ideas, and form valuable professional relationships.

Many participants remarked on the importance of expanding their networks to include experts from across the globe, recognizing that the challenges faced by the underground infrastructure sector demand international cooperation and knowledge sharing.

 

The event also fostered a deeper understanding of the role that global collaboration plays in overcoming regional sewerage challenges. By connecting with colleagues from various sectors, participants were able to share best practices and innovative solutions, which many are eager to implement in their own projects.

As the conference wrapped up, attendees expressed excitement for future events where they can continue to grow these professional networks and work together to tackle the challenges of modern urban drainage systems.

 

Conclusion: A Future Driven by Innovation and Collaboration

IKT’s 30th-anniversary conference was a landmark event, showcasing the latest innovations and research in sewer and urban drainage management. Attendees left with fresh insights and a renewed commitment to international collaboration. The conference not only deepened participants’ technical knowledge but also highlighted the importance of building lasting relationships with industry leaders worldwide.

As we look ahead, it’s clear that the connections forged and the knowledge shared at this event will continue to drive the development of resilient, sustainable infrastructure systems for the future. Participants are already looking forward to future IKT conferences, where they can continue growing their networks and contributing to the global effort of shaping the sewers of the 21st century.

IKT International Conference “Sewers for the 21st Century II” took place on 11. – 12. September 2024 in Gelsenkirchen, Germany.

Click here to view
all conference pictures:

Photo Gallery

 

 

 

Contact Persons

• Dr Iain Naismith
  T: +44 7983 605219
  E-Mail: naismith@ikt.institute
• Ashwini Ausekar, MSc.
  T: +49 209 17806-47
  E-Mail: ausekar@ikt.institute