<p>Making a positive impact on the planet motivates us to take on and solve global water challenges. Through our projects, we support the UN Sustainable Development Goals together with clients and partners from all over the world. From developing offshore wind farms, to safeguarding cities from flooding, protecting shorelines from erosion and enriching biodiversity in water basins. </p>

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How Söråker WWTP used a coupled groundwater-sewer model for a comprehensive evaluation with detailed insights 
 
The Söråker wastewater treatment plant (WWTP) in northern Sweden, operated by the water utility MittSverige Vatten, faced significant challenges due to high inflow and infiltration flows, particularly during snowmelt periods. These issues were exacerbated by the village's high groundwater levels, aging infrastructure and anticipated population growth. But by implementing a solution that integrates advanced technology with practical engineering, MittSverige Vatten has gained a detailed and holistic overview of hydrogeology and sewer networks for more efficient reduction of inflow and infiltration.
 
Challenge
 
Söråker's location on a slope near the Baltic Sea, combined with its glacial till soil composition, naturally led to elevated groundwater levels. Additionally, the village's infrastructure, including basements with drainage connected to the sewer network, contributed to excessive groundwater leakage into sewer pipes. Previous efforts, such as field surveys and scattered pipe relining, provided limited insights into these complex issues, jeopardising the WWTP's treatment efficiency and posing risks to residents and the environment.
 
Solution
 
In collaboration with DHI, Söraker WWTP implemented a multi-step approach:
 

Development of a coupled MIKE SHE groundwater-sewer model that allows detailed digital investigation of inflow and infiltration from groundwater and stormwater into the sewer network
Calibration of the model against groundwater monitoring points and total inflow to the WWTP
Evaluation of future scenarios involving strategies like deeper ditches, additional drainage and sewer pipe relining
Assessment of scenario impacts on inflow, treatment efficiency and groundwater levels. The integration of MIKE SHE and MIKE+ sewer models enabled detailed, physically based simulations, offering insights beyond traditional methods

 
Results
 
Söraker WWTP gained actionable solutions for informed decision-making that will enable them to accommodate the need for new housing areas at a reasonable cost and simultaneously reduce environmental impact on surrounding water environments. And by enhancing the operational and environmental efficiency of the existing WWTP, costly investments in upgrading the sewer network can be avoided. The implemented solutions are expected to alleviate the WWTP’s environmental load, enhance water quality and mitigate flooding risks. Results include:
 

An estimated investment savings of EUR 14 million by eliminating the need for costly investments in conventional sewer separation
A 30% reduction in biological oxygen demand (BOD) load to receiving waters, minimising environmental impact
Accommodation of new housing areas within existing WWTP permits thanks to reduced environmental impact from the WWTP


Lowering environmental impact of Germany’s first floating LNG terminal

Marine modelling studies contributed to the safe design of Wilhelmshaven LNG terminal and validated low environmental impact on nearby waters and nature reserves
 
Germany relies on various energy sources to ensure supply for citizens and businesses. In the wake of the Russia-Ukraine conflict, Germany took the initiative to build LNG receiving facilities at its Northern coast. Uniper started a project to build and operate the country’s first floating liquified natural gas (LNG) terminal with support from the government, which could provide up to 6% of the German gas demand. In building the terminal, there is a need to comply with safety and environmental obligations. DHI’s marine modelling studies and environmental impact assessments (EIAs) have helped Uniper establish safe design conditions and validated low environmental impact on nearby waters and nature reserves related to the terminal construction.
 
Challenge
 
Following the geopolitical situation and global natural gas supply crisis, Germany’s first LNG terminal in Wilhelmshaven gained rapid regulatory authority approval for construction in 2022. The terminal was built as a Floating Storage and Regasification Unit (FSRU), which is in fact a special vessel that receives LNG from arriving vessels and converts it back to its gaseous state. The vessel will have a fixed and secure berth at the existing transshipment facility. During the planning and implementation phase of port and terminal projects, the safety of terminal design and accurate predictions of potential impacts on marine ecosystems are important factors to consider. What’s more, Uniper was facing a tight timeline to ensure that the country’s energy supply would not be disrupted. As such, they urgently needed to establish environmental design conditions for the Wilhelmshaven terminal to quantify and manage risks and impacts.
 
Solution
 
DHI provided Uniper with modelling studies and EIAs related to the construction of the Wilhelmshaven terminal. The modelling results contributed to the terminal’s design, safety and operability, and the EIAs ensured that environmental impacts were kept to a minimum. The solution included:
 

A detailed metocean study to get a full picture of the hydrographic conditions, such as wind, water levels, currents and waves
Environmental data for navigational safety for inbound and outbound carriers carried out in a Full Mission Bridge Simulator by our partner Nautitec
An investigation of dynamic mooring forces and vessel motions not only for the Wilhelmshaven terminal itself but also when an LNG carrier is moored simultaneously. This led to the identification of design conditions for the bollards and fenders of the terminal and threshold conditions for safe mooring.
Environmental impact assessments- Biocide concentrations: The public and mussel farmers in the area were concerned about the possible increase in biocide concentrations due to the terminal in Wilhelmshaven. The LNG terminal has been in operation for a year and is regularly monitored by the authorities with regard to the use of biocides. A so-called monitoring, which examines the effects on the Jade and the Jade Bay, has not identified any negative effects on the water after one year of operation. The discharge of cooled water in summer and heated water in winter was also no longer measurable in the water itself.- Fish and larvae migration: As the released water from the terminal is either warmer or colder than the ambient water, there were concerns that fish and larvae would not swim through it. DHI validated that no ‘temperature barriers’ have formed around the terminal and thus fish and larvae migration would not be affected. DHI also helped assess the potentially dangerous areas for fish and larvae in the vicinity of the terminal’s inlets. Knowledge of the extent of the affected area would allow Uniper to implement compensation measures.

 
Results
 
In December 2022, the Wilhelmshaven terminal started operations with its first import of LNG, sufficient to supply energy to 50,000 German households for a year. The terminal will handle 6% of Germany's future gas requirements and serve as a bridging technology towards a green future. In a later phase, the terminal will be equipped to switch to imports of low-carbon energy sources such as green hydrogen. DHI’s solution has:
 

Contributed to the fast operation of the Wilhelmshaven terminal thanks to accurate simulation covering hydrodynamics, thermodynamics, chemistry, waves, wind and dynamic mooring
Validated the low environmental impact of the terminal construction on nearby waters and nature reserves
Helped Germany ensure sufficient energy to power homes and businesses


Taking seabird flight registration to new heights

A DHI study for Vattenfall measures seabird collision risks and can help speed up offshore wind farm approvals
 
A DHI study for the European energy company Vattenfall finds that seabirds deliberately avoid rotor blades at offshore wind farms. The findings could help pave the way for a faster permit process. The study mapped the flight paths of thousands of seabirds around wind turbines in the North Sea, and during two years of monitoring using cameras and radar, not a single bird was recorded colliding with a rotor blade. The results could pave the way for simpler permit processes for offshore wind power by improving our knowledge about seabird collision risk.
 
Challenge
 
Demand for more renewable energy is soaring, and the offshore wind sector is constantly developing to keep up. However, the slow permit processes for establishing new offshore wind farms make it challenging to accelerate growth in the sector. The environmental impact assessment required in the permit process typically includes studies on how the proposed new wind farm will impact seabirds and marine life in the area. But it has previously been challenging to carry out research on the collision risk for birds at offshore wind farms due to lack of technical monitoring solutions and the severe weather conditions which has made the task of accurate monitoring and registration more difficult.
 
To overcome this challenge, a study was commissioned by the energy company Vattenfall to be carried out at the Aberdeen Offshore Wind Farm in the North Sea on the east coast of Scotland.
 
Solution
 
The movements of herring gulls, gannets, kittiwakes and great black-backed gulls at the Aberdeen Offshore Wind Farm were studied in detail from April to October in 2020 and 2021 when bird activity is at its highest in this region. This was the first time that any kind of bird species has been studied this closely and in detail at an offshore wind farm. The research team was led by DHI, and the team combined radar data with cameras to identify the species of seabird and create a three-dimensional image of birds’ flight patterns and how they avoid rotor blades. By combining the two, the researchers were always able to record where each bird was and what the bird was doing in relation to wind turbines, the distance to them and current weather conditions.
 
The system was able to track birds across both cameras, which was supported by an artificial intelligence system with high tracking accuracy. The study also took into account the turbulence from the back of the turbines in addition to wind and weather conditions.
 
The research team placed a camera with a 220-degree view on two of the 11 wind turbines – in the middle and at the edge of the wind farm – and a radar device covering the entire wind farm. The system first detected the approaching birds by radar and automatically handed them over to the cameras for further tracking. A total of 1,753 coupled tracks were recorded during 2020 and 1,370 tracks during 2021. Detailed statistical analyses of the seabird flight data were enabled both by the large sample sizes and by the high temporal resolution in the combined radar track and video camera data (2.5 seconds).
 
Results
The data showed that seabirds will be exposed to very low risks of collision in offshore wind farms during daylight hours. No collisions or even narrow escapes were recorded in over 10,000 bird videos during the two years of monitoring covering the monitoring period.
 
The results of the study show that it is possible to predict collision risks more accurately and allow more realistic figures to be derived for estimates of the cumulative effect of wind farms. Similar studies could be done for future offshore wind farm sites, ultimately paving the way for simpler permit processes for offshore wind power without compromising on the protection of vulnerable seabird species.

Mapping submerged navigational hazards in the Arctic 

Satellite tool enables detailed large-scale mapping to make it safer to navigate Greenland’s arctic waters
 
Climate change is widening the areas of operation in the Arctic, with ice-free conditions enabling the expansion of economic activities, access to natural resources and opening of new shipping routes. However, navigating in Arctic waters poses significant challenges due to the lack of precise nautical charts. This leaves mariners reliant on personal experience and onboard equipment, which is inadequate as decision support in route planning outside existing routes. Together with the Royal Danish Navy, DHI has developed a satellite-data-based tool enabling safer navigation in the coastal Arctic waters of Greenland. In collaboration with the Nordic Institute in Greenland, local knowledge is now being included in this tool, enabling stakeholders across the Arctic to plan routes for a wide range of civil and naval tasks, improving safety for local communities and the fragile marine environment.
 
Challenge
 
Maritime activities in the Arctic are growing, and the region is becoming increasingly important from a geopolitical perspective. But it is not easy to navigate in the Arctic region as nautical charts are generally not up to date, and the positional accuracy is often inadequate even in the close vicinity of settlement areas. Maritime operations in the Arctic are therefore often associated with navigational risks. This hinders tasks and activities such as recreational navigation, operating commercial or scientific vessels and search-and-rescue operations.
 
To ensure that these activities can be carried out safely, local stakeholders need a risk-mapping solution to improve navigation in remote areas with little or no chart coverage. This need was highlighted by the grounding in 2023 of the cruise liner Ocean Explorer. The ship got grounded in the remote Alpe fjord in Northeast Greenland because of insufficient hydrographic data. Luckily, there were no human or environmental catastrophes.
 
Solution
 
To address the challenges, DHI worked with key Arctic stakeholders including the Royal Danish Navy, to develop a satellite-based tool called NANOKnavi. Nanok means polar bear in Greenlandic.
 
The Nordic Arctic Co-operation Programme, administered by the Nordic Institute in Greenland helped finance the investigation of how local expert knowledge can enrich and validate the machine-learning-based NANOKnavi data product. By bridging local knowledge and satellite-based mapping in collaboration with Greenlandic and Swedish first responders, Greenlandic pilots and Greenlandic tourist operators, the novel NANOKnavi data products are benefitting sustainable development for the people of the Nordic Arctic.
 
The tool minimises navigational risk and increases environmental situational awareness by mapping submerged rocks, intertidal zones and coastlines and is ideal for shallow depth areas in the remote and poorly charted areas across the Arctic region. The mapping is based on DHI’s automated remote sensing processing chains, including a proprietary machine-learning model based on open-source satellite data, validated against in-situ multi-beam echo-sounding data. By using satellites to map the coastal zone, dangerous shallow waters across vast regions can be mapped very quickly – a task that would be impossible with any other technologies such as traditional vessel-based surveys or drones.
 
A key aspect in the development of NANOKnavi was the involvement of local navigators to make sure that their knowledge and experience with the local waters were included in the final solution. And that their navigational needs were met to ensure the safety of everyone.
 
Results
 
Building on satellite data, users can be certain that their GPS position matches their position on the NANOKnavi map. Relying on detailed and up-to-date satellite data instead of decades-old surveys, NANOKnavi equips navigators with an overview of subsurface hazardous rocks, tidal zones and coastlines.
 
The result is peace of mind for navigators of the Arctic waters around Greenland, whether it is a local fisherman, a captain on a naval ship or a cruise ship or environmentalists seeking to protect marine life and biodiversity in the Arctic region.

Exploring the potential of counter-current AB process (CCAB) applications in Denmark
Treatment of wastewater is required to reduce the carbon content as well as pollutants in the wastewater to mitigate eutrophication of the receiving water bodies. This process requires significant amounts of energy for pumping and aeration. Harvesting carbon (measured as chemical oxygen demand – COD) in the primary stage at the WWTP could be a cost-efficient way to lower energy requirements while using the removed carbon for biogas production. DHI received funding from the Market Development Fund to develop a new concept for COD harvest and to implement it in the primary stage at Esbjerg East WWTP, Denmark. With input from other Danish utilities, DHI developed the new counter-current AB process (CCAB), which increased COD harvest in the primary clarifier from 30% to 62%.
 
Challenge
The Danish Water and Wastewater Association performs a yearly benchmark of Danish WWTPs, which has revealed that in recent years, an increasing number of utilities have become energy neutral. This trend is expected to continue as it corresponds with local and national political goals. While WWTPs need significant amounts of energy for pumping and aeration, fortunately, utilities can claim major savings by improving treatment efficiency and increasing on-site energy production through anaerobic digestion of the primary sludge.
Existing technologies for increased COD harvest are costly and require high maintenance
 
Two commercially available technologies for increased COD harvest from municipal wastewater dominate the market: fine-mesh sieving (filtration) and chemically enhanced primary clarification. Both offer increased COD harvest compared to traditional methods, but unfortunately include significant downsides. Filtration requires advanced machinery with costly maintenance, while chemically enhanced clarification produces a high amount of inert chemical sludge that does not contribute to biogas production and generates additional load on the sludge handling systems.
 
Solution
Laboratory tests were carried out to determine the potential of CCAB operation before full-scale implementation and during full-scale operation at Esbjerg East WWTP. Good correlation was shown between lab and full-scale results. This allowed DHI to use lab-scale tests as an indicator of COD harvest potential of the technology. Advanced online process control was installed to ensure stable operation and sampling campaigns were performed to determine the actual COD harvest and used as input to model the CCAB process.
 
The modelling software WEST was used to run simulations of the baseline (current) operation of four WWTPs in Denmark. The results were compared to three alternative technologies with primary COD capture. The simulated scenarios included filtration, chemically enhanced clarification and CCAB systems. The endpoints for evaluation and comparison of the different scenarios were: (i) COD load provided for anaerobic digestion, (ii) power consumption for aeration and (iii) external carbon dosing to meet denitrification needs.
 
Results


Higher COD harvestLab-scale tests and full-scale operation showed comparably high COD harvest in the primary stage, from 30% to 62%. This number compares favourably with other commercially available technologies.


Potential for increased efficiency (WEST results)The CCAB process showed a positive impact on the energy production due to a doubling of the COD harvest in the primary stage. Furthermore, removing COD in the primary stage proportionally reduces aeration needs in the biological stage. A comparison of the test period with a similar period during baseline operation showed approximately 40% increased energy efficiency.


Significant savings with short ROI timesThe business cases evaluated favour CCAB operation in three out of four plants. CCAB operation is economically feasible at plants with existing primary clarifiers (ROI &lt; 2 years) but also in cases where primary clarifiers would have to be built (ROI &lt; 6 years). In all three cases, the yearly savings were higher for CCAB compared to any other scenario.



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