Cases and challenge owners
BlueGreen Innovation Challenge 2026
Case 1
How can AI and data make sewer network maintenance more precise and intelligent?
Beneath our cities lies an extensive sewer network that requires continuous maintenance and renovation. But how do we know where to act first? This case explores how AI, CCTV inspections, data, and digital platforms can be combined to provide utilities with a stronger basis for detecting damage, predicting remaining service life, and prioritising investments.
Additional information
The sewer system is one of society’s largest hidden infrastructures. Beneath our cities lie thousands of kilometres of pipes, manholes and structures that continuously age, are exposed to various stresses and develop damage. At the same time, investments in maintenance and renovation are substantial, and utilities face the challenge of avoiding both premature renovation and waiting until damage develops into an acute problem.
Traditionally, sewer system monitoring relies on CCTV inspections, where an operator reviews footage and assesses the condition, damage and need for intervention. This process is time-consuming, dependent on individual assessments and difficult to scale across large sewer networks.
How can artificial intelligence and digital platforms support more systematic and data-driven monitoring of sewer systems?
Machine learning is already used in many situations where little or no information about the system is available. But can it be made more relevant to the specific location with only a limited effort or cost?
The case focuses on the use of AI for analysing and assessing sewer networks. One example is the automated analysis of CCTV inspections, where AI can identify and classify damage. But could AI also identify incorrect connections, detect unwanted rainwater entering combined sewer systems, and estimate the remaining service life of different components within the sewer system?
Can AI and digitalisation be integrated even further into processes for prioritising investments and infrastructure projects across sewer networks?
The goal is not simply to identify faults, but to transform large amounts of data into decision support and generate real-world data where information is currently lacking. This can help utilities prioritise investments, plan renovations and optimise infrastructure operations.
The case will explore the intersection between existing data and the generation of real-world data for prioritising infrastructure investments, using the opportunities currently available within software development, AI, digitalisation and data platforms. Technical knowledge of sewer system design, materials, damage mechanisms and service life provides the foundation. The question is how these areas of expertise can be combined so that digital tools support better decisions and more precise investment strategies.
Participants are encouraged to think broadly and explore how the digital monitoring of future sewer systems can create greater value for utilities, citizens and society through better data quality, more accurate forecasts and smarter use of resources.
Case Owner:
Samn Forsyning
Case 2
Can we use rainwater evaporation for both climate adaptation and better, greener urban spaces?
Rainwater does not necessarily have to be drained away or infiltrated into the ground. This case explores how evaporation can become a measurable and documented part of urban climate adaptation. The task is to develop urban solutions or installations that combine water management with elements such as vegetation, shade, recreational spaces, and biodiversity – while functioning effectively during both droughts and heavy rainfall.
Additional information
Research into evaporation as a climate adaptation solution is already underway, particularly at the Danish Technological Institute and the University of Copenhagen, with several examples of pilot solutions. Projects such as Grøn Gentagelse and the DAMP evaporation project in Folehaven demonstrate that evaporation-based solutions can work in practice. However, these solutions are still at the pilot stage, and further work is needed to establish how evaporation can become an integrated part of broader rainwater management.
When we discuss rainwater in cities, the focus is often on draining it away, slowing its flow, allowing it to infiltrate into the ground or treating it. Yet evaporation is also part of the natural water cycle. In densely built-up urban areas, evaporation can be an overlooked process, despite its potential to reduce water volumes, improve the microclimate and create greener, more pleasant public spaces.
The challenge is that evaporation is rarely included as an explicit and documented component of climate adaptation solutions. How much water can actually be removed through evaporation? Which materials, plants, surfaces and structures enhance this effect? And how can solutions be designed to deliver both technical benefits and added value for public spaces?
This case focuses on developing new products or types of installations for public spaces that actively use the evaporation of rainwater. These could combine water retention, planting, surfaces, street furniture, shade, places to sit and relax, and biodiversity.
Participants will explore how evaporation can become a practical component of climate adaptation. Where can the solution be located? What volumes of water can it manage? How will it perform during dry periods and heavy rainfall? How will it be operated and maintained? And how can its effect be documented to ensure that it becomes not just a green feature in a public space, but a genuine part of rainwater management?
The case aims to connect technical water management with high-quality public spaces. It is not simply about removing water, but about using it actively to create better cities.
The central question of the case
Can we develop products for public spaces that make evaporation a measurable part of climate adaptation while creating more comfortable places to spend time, adding greenery and enhancing the quality of urban spaces?
Case Owner:
Danish Technological Institute
Case 3
What will it take to make the waters around Haderslev clean enough for swimming?
Haderslev lies between Haderslev Dam and Haderslev Fjord, but algal blooms and poor water quality currently limit opportunities for swimming. The case challenges participants to turn existing knowledge into a realistic roadmap for better bathing water quality – combining technical measures with regulation, financing, stakeholder involvement, and tangible benefits for citizens.
Additional information
Haderslev is uniquely located between Haderslev Dam and Haderslev Fjord. Clean, accessible water could strengthen everyday life for citizens and support recreation, health, tourism and the city’s blue identity.
Today, both water bodies are affected by historical pollution, nutrient pressure, urban runoff and physical changes. In summer, algae blooms and poor water quality can make the water unsuitable for bathing.
The challenge
This case asks: When can citizens safely take a dip in Haderslev – and what will it take technically, legally, economically and socially to get there?
The goal is to turn existing knowledge into a realistic roadmap for better bathing water quality in and around Haderslev.
Focus areas
- What are the main causes of algae blooms and poor bathing water quality?
- What is the gap between current conditions and safe, attractive bathing water?
- Which measures could reduce nutrient loading and create visible value for citizens?
- How can technical solutions be combined with legal requirements, financing, stakeholders and maintenance?
- How can citizens, landowners, authorities and local businesses be engaged around a shared benefit?
Expected outcome
Participants will receive background data and knowledge from previous investigations into water quality, catchment pressures, existing projects and local conditions. Based on this, the group will develop a practical roadmap towards improved bathing water quality.
The roadmap should include proposed measures, key stakeholders, implementation steps and a rough economic estimate. The ambition is to create a solution that is realistic for Haderslev and useful for other Danish towns facing similar water quality challenges.
Case Owners:
SEGES Innovation and Haderslev Municipality
Case 4
How can rainwater and groundwater be collected and used as a resource across an entire urban district?
At Winsløwparken, water should not simply be drained away – it should be considered a valuable resource. This case explores how rainwater and groundwater can be collected, treated, stored, and shared between buildings and future property owners. The task covers everything from nature-based and technical solutions to data, management, ownership structures, and models for a shared local water supply.
Additional information
Water is one of the city’s most overlooked resources. During some periods, we face challenges from large amounts of rainfall, while during dry periods there is demand for water for urban nature, cooling, operations and other purposes. Nevertheless, rainwater is often managed as something that should be drained away as quickly as possible rather than as a resource that can be stored, shared and used when needed.
The case focuses on creating an integrated water cycle for the urban district. How can rainwater and groundwater become active resources in the development of a new urban area? How can nature-based and technical solutions work together to treat, store and make water visible? And how can the resource subsequently be shared across buildings, functions and future properties?
Winsløwparken faces a particular challenge and opportunity. The area is being transformed from a single property into several future properties with different owners, interests and needs. At the same time, groundwater is already being managed in the area, opening up new opportunities to consider water as a shared resource rather than an individual challenge.
We are looking for solutions that can:
- Create a robust local system for collecting, treating, storing and using water.
- Develop models for sharing water between buildings, functions and owners.
- Use digitalisation, data and intelligent control systems to document water quality and available volumes, while supporting operations, decision-making and trust between stakeholders.
The goal is not simply to establish a rainwater system or a technical utility solution. The goal is to develop an integrated water system in which the value of water is retained for as long as possible and where the resource can move to where it creates the greatest benefit for people, nature and the city.
How can we create a water system where no drop goes to waste and where water can be collected, shared and used across the entire urban district?
Case Owner:
Freja Ejendomme
Case 5
How can we reduce sewer overflows while creating a healthier and more attractive urban stream?
An urban stream in Randers is affected by combined sewer overflows and wastewater-related pressures, while space for traditional solutions is limited. This case challenges participants to rethink approaches to retention, treatment, disconnection, and compact solutions to reduce pollution, improve ecological conditions, and enhance the stream’s recreational value.
Additional information
In many older urban areas, rainwater and wastewater flow through the same sewer system. When the system becomes overloaded during rainfall, overflows into nearby streams can occur. This means that it is not only rainwater, but rainwater mixed with wastewater that ends up in the receiving water body.
This case focuses on an urban stream that is currently affected by overflows from the combined sewer system and wastewater-related pressures from a nearby hospital area. The stream flows into the Gudenå River and is also located in an area where it has the potential to become a green and recreational space for local citizens.
The challenge is that the stream’s potential does not match its current condition. Pressure from the combined sewer system is an obstacle to achieving good ecological status, while space around the stream is limited. There are no obvious large areas available for traditional retention basins, temporary water storage or treatment solutions, making it difficult to implement new discharges and improvements in the conventional way.
The case is about thinking outside the box and identifying new ways of reducing the pressure from the combined sewer system. Can the water be detained, controlled, treated or managed differently? Can parts of the catchment be disconnected? Can compact solutions be implemented where space is limited? And can the hospital area or surrounding urban spaces become an active part of the solution?
The goal is to develop a concept that reduces the discharge of wastewater-contaminated rainwater into the stream, supports progress towards good ecological status and at the same time creates a more attractive recreational area for the city.
The central question of the case is: How can an urban stream that is currently affected by combined sewer overflows and wastewater-contaminated rainwater be transformed into a healthier stream with greater recreational value for the city’s residents?
Case Owner:
Randers Municipality
Case 6
A city with water on all sides
A small Danish city surrounded by hills, streams and lakes faces a growing challenge from rainwater runoff and flooding. This case explores how nature-based solutions such as rain gardens, green surfaces and permeable pavements can complement traditional drainage infrastructure. The challenge is not only to find the right solutions and locations, but also to consider maintenance, costs, biodiversity, climate resilience and how local stakeholders can become actively involved.
Additional information
Imagine a small city of just over 4.500 inhabitants. It is a lovely place situated between steep forested hills and one of Denmarks largest streams and lakes.
But the city is not without its issues – and one of them is rainwater runoff. When a city is in a hilly area rainwater from a potentially large area may concentrate downhill. And having a stream right on the other side of the city guarantees a minimum water table all year long. And a city means lots of impermeable surfaces. Altogether this creates the risk of flooding of homes and businesses, cellars and garages and more. In Denmark, flood damages cost municipalities, business owners and private property owners around 7 billion DKK each year. This figure is expected to rise to 12 billion in 2050 and 27 billion in 2100, calling for urgent action and future climate adaption/proofing of vulnerable areas not only locally but on catchment scale.
Hystorically, urban water management and flood prevention has relied on increasing grey infrastructure capacity – such as increasing stormwater pipe sizes and wastewater plant capacity. However, this approach is capital and material intensive, imposes heavy nuisances on citizens and is not future climate change proof, as if climate extremes continue to rise, new rennovations and capacity increases will become inevitable.
Therefore, turning to a new nature-based approach has become more popular. Introducing green, permeable areas in cities such as rain gardens, green roofs or walls, or nature inspired infrastructure such as permeable roads, pavements and parking lots, the permeability and water storage capacities of cities can be increased, thus preventing water from accumulating in said vulnerable areas and causing floodings. However, this approach is relatively new and needs to be seamlessly implemented in urban areas in a way that is functional, easy to maintain for public and private stakeholders, is accepted and preferred by citizen rather than a cause for concern and provides multiple other benefits and opportunities – e.g. biodiversity, heat island mitigation, noise and air pollution reduction as well as social and psychological benefits for local communities. In light of all this here is our challenge:
How can Nature Based solutions help mitigate the challenges with rainwater runoff in a typical Danish city?
· What types of NbS would fit within the local infrastructure?
· Where do we put them so we maximise benefits, and minimise implementation difficulties and costs as well as future maintenance
· How do we get the local stakeholders involved? – Not just in the planning and implementation phase, but also in the maintenance and future development of new green and green-grey areas.
This case is part of the completion of the Cure-NbS project on Nature Based Solutions.
Case Owner:
BYKVAD, Via University College
Case 7 – Postponed
Electrocoagulation as Integrated Stormwater Treatment
Many rainwater solutions are effective at retaining water and particles but are less capable of removing dissolved substances such as zinc, copper and phosphorus. This case explores how electrocoagulation can be used as a compact treatment technology and integrated directly into existing pipes, manholes, basins and underground rainwater systems.
Additional information
Many rainwater solutions are effective at retaining water and removing particles, but they are less effective at removing dissolved substances. This is particularly the case for heavy metals such as zinc and copper originating from urban areas, roofs, roads and heavily trafficked surfaces. When these substances are discharged into streams, lakes or coastal waters, they can negatively affect the aquatic environment and make it more difficult to achieve good ecological status.
This case focuses on electrocoagulation as a compact technology for rainwater treatment. The technology is based on an electrochemical process in which aluminium electrodes can help bind and remove dissolved substances from the water. However, the challenge is not only whether the technology works, but also how it can be designed and integrated into existing infrastructure and systems.
How can an electrocoagulation cell be incorporated into existing pipe systems, manholes, storage facilities or underground treatment units? Could it be installed upstream of a wet pond, allowing the water to be treated before being discharged further? Or could it be integrated directly into the pond as a floating, submerged or fixed installation?
Participants will work with either treatment efficiency, physical integration or operation. The solution must function hydraulically, be accessible for maintenance and be suitable for real-world rainwater systems where space is often limited. Consideration must also be given to control systems, energy consumption, electrode replacement, documentation and the potential for implementation in both new and existing facilities.
The central question of the case is: Can electrocoagulation be developed into a compact and well-documented rainwater treatment technology that removes dissolved heavy metals while also being practically integrated into pipe systems, underground infrastructure and wet ponds?
Case Owner:
Aalborg University
Case 8
From Wastewater to a Blue-Green Ressource
Climate change is increasing pressure on sewer systems and wastewater treatment plants, while more areas are experiencing drought and challenges related to water balance. This case explores how Rhizop’air and LARS can be used for nature-based treatment and local reuse of treated wastewater. The aim is to view water as a resource that can remain in the landscape and contribute to nature, groundwater recharge and climate adaptation. Participants will develop a concept for how the solution can complement existing wastewater infrastructure, with a focus on operation, documentation and scalability to other areas.
Additional information
Climate change is leading to more intense rainfall events, and during peak loads, significantly larger volumes of water can enter wastewater systems. This puts pressure on both sewer networks and wastewater treatment plants and increases the need for solutions that can complement existing grey infrastructure.
At the same time, treated wastewater is often discharged away from local catchments, while more areas are experiencing periods of drought and increasing pressure on the local water balance. This raises an important question: Can treated wastewater become a local resource rather than simply something that is transported away?
This case focuses on Rhizop’air and LARS – local discharge of treated wastewater. Rhizop’air is a nature-based treatment technology in which wastewater is treated biologically through a planted system consisting of an upper root zone and a lower actively aerated zone. The technology should be integrated with local discharge, infiltration or reuse, allowing the water to remain in the landscape and contribute to nature, water balance and local resilience.
The challenge is not only technical. The case explores how nature-based wastewater treatment can become part of a wider blue-green landscape in which water and nature are considered together. How can treated wastewater support drought-affected landscapes, reduce pressure on sewer systems and create value for citizens, agriculture, nature and groundwater?
Participants will develop a concept showing how Rhizop’air and LARS can complement existing wastewater infrastructure. This could be implemented as a local solution in smaller communities, as part of a climate adaptation project, as a water bank in the landscape, or as a model for how treated water can be reused and create new value.
The case must also address the questions that determine whether the solution can be scaled: Who owns the water? Who is responsible for operating the system? How can its impact be documented? How can the value of keeping water within the landscape be measured? And how can the solution be replicated in other cities and regions?
The aim is to develop a solution concept, model or roadmap showing how decentralised nature-based wastewater treatment and the local use of treated water can contribute to more resilient blue-green landscapes.
The central question of the case is: How can treated wastewater become a local resource that strengthens water balance, nature and climate adaptation rather than simply being discharged away?
Case Owner: