Proper management of wastewater is necessary to protect both people and ecosystems. Wastewater management enables the harvesting of the many resources wastewater and treatment holds.
The perspective on wastewater is shifting from a waste byproduct to a valuable asset. We have gathered five cases proving that wastewater can be a key contributor to both environmental and economic sustainability.
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Launched at the IWA World Congress & Exhibition 2024 in Toronto, a new edition of the white paper "Unlocking the potential of wastewater" presents insights and solutions from Denmark's water sector on viewing wastewater as a resource while safeguarding people and ecosystems.
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The water sector is facing a growing number of challenges affecting all aspects of operations. Taking a data-driven approach to running a wastewater treatment plant opens new opportunities for optimisation. The Danish water sector has already proven that digitalisation holds the key to radical transformation.
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Dive into our digital visualisation of Denmark’s water value chain, and discover companies and organisations that specialise in water-related technology, research, and innovation.
Discover the Danish water value chainEvery day, billions of litres of wastewater flow through pipes, treatment plants, and back into nature. For a long time, this was thought of as a problem to manage. Denmark decided to think differently, and treat it as an opportunity.
Today, Danish wastewater treatment plants don’t just clean water. They produce energy, recover nutrients, and help power entire neighbourhoods. And they do it while protecting rivers, coastlines, and drinking water for millions of people.
Download the latest white paper to learn more.
Denmark started taking wastewater seriously in the 1980s, when its lakes and coastal waters were showing clear signs of damage. Strict rules were introduced. New technologies were developed. And over time, a culture of innovation took hold.
The results speak for themselves. Today, more than 95% of all wastewater in Denmark is treated to the highest biological standard. The sector aims to be fully energy neutral by 2030, and some plants are already producing more energy than they consume.
Energy. When organic matter in wastewater breaks down, it produces biogas. That gas is used to generate electricity and heat — which can power the treatment plant itself, and even supply nearby homes through district heating networks.
Fertiliser and soil improver. The solids left over after treatment — called sludge — are rich in phosphorus and other nutrients. Instead of throwing them away, Denmark uses advanced processes to turn them into safe, valuable materials for agriculture.
Clean water for industry. Industrial facilities can treat their own wastewater on-site and reuse it in production processes, reducing pressure on freshwater sources. Carlsberg’s largest brewery in Denmark, for example, treats and recycles 90% of its process water on-site, cutting both water consumption and wastewater discharge.”
A foundation for green energy. The hydrogen economy needs enormous quantities of ultra-pure water. Treated wastewater is one of the most promising sources — meaning wastewater plants could become a critical part of tomorrow’s clean energy infrastructure.
Denmark’s approach to wastewater shows what is possible when regulation, investment, and long-term thinking work together. The results are real — but so are the remaining challenges. PFAS contamination, greenhouse gas emissions from treatment processes, and the energy demands of advanced purification are problems the sector is still working to solve.
The technologies being developed and tested in Denmark are not exclusive to Denmark. They are scalable and have already been applied in Singapore, the United States, China, Italy, and Germany, among others. But scaling them requires commitment, from governments, utilities, and industries alike.
Wastewater is one of the most underused resources we have. Using it better is not a silver bullet for the water or climate crisis. But it is a meaningful and necessary part of the solution.
Denmark’s wastewater sector demonstrates how treatment plants can serve multiple purposes at once, producing energy, recovering nutrients, protecting water quality, and supporting climate targets. The best solutions solve more than one problem at the same time. Achieving this, however, requires close collaboration between authorities, utilities, research institutions, technology providers, and industries.
Dive into the digital visualisation of Denmark’s water value chain, and discover companies and organizations specialising in wastewater treatment, resource recovery, and digital innovation.
Explore the water value chainIn this Q&A, we explore why wastewater management plays such a central role in Denmark’s water-flow, how wastewater management supports climate targets, and what makes the Danish model a source of inspiration for policymakers and water-technology developers worldwide.
In 2022, 95.7% of all wastewater in Denmark underwent full biological treatment. More than 95% is subject to tertiary treatment, one of the highest rates globally. This results from strict regulations since the 1980s, a discharge-tax system, and public-private climate partnerships. Globally, around 20% of household and industrial wastewater is properly treated.
Danish plants convert organic sludge into biogas through anaerobic digestion. The biogas powers combined heat and power (CHP) generators producing electricity and heat. Excess heat feeds district heating networks. Some plants also use heat pumps drawing on the temperature of treated effluent. Danish plants achieve 77% net energy self-sufficiency; several are now net energy producers. The sector’s 2030 goal is full energy neutrality.
Resources include: phosphorus and nitrogen (as fertilisers), biogas (energy), biochar (soil amendment and carbon sink), heat (for district heating), and water (for industrial reuse). In 2021, 76% of Danish sewage sludge was applied to farmland. Newer pyrolysis technology converts sludge to biochar at 500-800°C, eliminating PFAS while locking 28-50% of the carbon in stable form for centuries.
A digital twin is a real-time virtual model that mirrors the physical plant. It integrates online sensor data with process simulation models, letting operators test operational strategies in a virtual environment before committing to real changes. The digital transformation of the wastewater sector explores how these technologies enable scenario-based optimisation and real-time performance monitoring.
PFAS (‘forever chemicals’) are around 10,000 synthetic substances that persist indefinitely in the environment. Standard municipal plants are not designed to remove PFAS. Technologies under development include foam fractionation, flocculation with FluorFloc, and ion exchange resin columns. Pyrolysis at high temperatures fully destroys PFAS compounds, offering a promising solution for eliminating these contaminants from sewage sludge. Denmark has co-proposed an EU ban on 10,000 PFAS substances.
Denmark charges treatment facilities a discharge tax per kilogram of organic matter (BOD), phosphorus, and nitrogen discharged, creating strong financial incentives to invest beyond regulatory minimums. The 2023 EU Urban Wastewater Treatment Directive extends this to cosmetics and pharmaceutical industries, who must fund at least 80% of the fourth treatment step costs.
Power-to-X, converting renewable electricity into hydrogen or synthetic fuels via electrolysis, requires very large volumes of ultrapure water. Treated wastewater is a candidate source, requiring advanced oxidation, membrane filtration, and multi-stage biological treatment. Research into groundwater, seawater, and treated wastewater as input sources is actively underway in Denmark.
Perspective
Groundwater management
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