From wastewater to a sustainable sip: pioneering water reuse
Water – a molecule so simple yet indispensable – is under unprecedented pressure. Across the globe, freshwater supplies are being strained by extreme weather events, population growth and urban demand. By 2030, it is expected that global water demand will exceed supply by 40%.1 The challenge of water scarcity is felt around the world, with one in four cities facing water insecurity.2 Even water-rich countries such as Germany have experienced severe shortages in recent years.3 As global water demand continues to rise, the need for smart, resilient water systems and locally available water resources has never been more urgent.
Reusing treated wastewater is one viable solution – and it’s already happening in innovative ways. One of these examples is Reuse Brew, a project that turns recycled water into high-quality water suitable for brewing beer. This is a major step forward, showing that advanced water reuse technologies are not only feasible but practical and safe – even for applications traditionally associated with high-quality potable water.
Why reuse matters – and why now
Water reuse is not a futuristic concept. Historically, communities have recycled water in various forms for agriculture, industry, and even indirect potable purposes. Notable examples include the Orange County Groundwater Replenishment System in California and Namibia’s Goreangab Water Reclamation Plant in Windhoek – operating since 1968 – which recycle treated effluent back into the municipal drinking water supply without any recorded public health issues.
Today, the need for reuse is driven by clear environmental and social imperatives. Freshwater sources are being depleted faster than they can be recharged. Climate change is increasing the frequency of droughts and heatwaves, while urbanisation concentrates demand in places already stressed by limited water resources.4 In Europe, southern nations such as Spain and Greece are pushing forward reuse for agricultural irrigation, and projects are multiplying across Germany, France, and beyond.
Wastewater is a particularly promising resource because it’s continuous – it flows regardless of drought or dry season – and its treatment for reuse is often more sustainable and cost-effective than alternatives like transporting water over long distances from reservoirs. This has been realised in Singapore, as recycled wastewater can now meet 40% of the country’s water demand and this figure is rising.5 Yet globally, just 11% of wastewater is reused.6 This gap reflects not a lack of potential, but the fact that many regions still lack the infrastructure, regulatory frameworks and investment needed for advanced treatment technologies.
Reuse Brew harnesses this largely untapped resource not just to produce a beverage but to spark vital conversation about the critical role of water reuse in building more reliable and resilient water systems for the future.
A sustainable revolution in a glass
Reuse Brew was conceived as a collaboration between Xylem, a global water solutions company, and the Technical University of Munich, to showcase the effectiveness and readiness of advanced water treatment technologies. Its mission is both symbolic and practical: demonstrate that treated wastewater can be refined to such high quality that it can safely be used for beer production – where consumers expect purity and flavour. Each treatment step is engineered to transform the wastewater to higher stages of purity until it reaches the quality threshold or higher for drinking water required for brewing.
For this year’s Reuse Brew, Xylem is collaborating with partners from the Nutzwasser project7, including the municipal wastewater treatment plant in Schweinfurt, Germany. Within the Nutzwasser project, researchers and practitioners are exploring how advanced treatment processes can be leveraged at varying scales – and under real-world operating conditions – to provide high quality water for applications like agricultural irrigation, urban landscape irrigation, and other uses identified in regional water strategies.
The Nutzwasser project is currently in its demonstration phase at the Schweinfurt plant and is processing wastewater using a combination of treatment steps, which will be implemented at full-scale by 2028. The steps include filtration, ozonation, biologically activated carbon (BAC) filtration, granular activated carbon (GAC) filtration, and UV disinfection. For Reuse Brew, the water is diverted after UV disinfection and run through additional advanced treatment processes using nanofiltration and Ultraviolet Advanced Oxidation (UV-AOP). The process includes several specific steps that ensure high quality standards, with each successive stage applying increasingly exacting filtration to remove remaining contaminants and ensure the water meets high standards of quality and safety required for human consumption.
How Reuse Brew treats water
The purification journey begins at the water reclamation facility in Schweinfurt, Bavaria. Here, the effluent from conventional wastewater treatment – already cleared of solids and major organic pollutants and nutrients – undergoes an advanced series of purification steps to produce water of exceptional quality. The journey continues to the Technical University of Munich, where additional treatment is applied at the Chair of Urban Water Systems Engineering to provide brewing quality water, before it ends at the Chair of Brewing and Beverage Technology to be transformed into a Bavarian Helles.
1. Conventional wastewater treatment
At the Schweinfurt plant, raw sewage goes through mechanical treatment and biological nutrient removal processes. This stage removes solids and reduces common pollutants such as organic matter, phosphorus, and nitrogen. The effluent from this stage is suitable for discharge into rivers but still contains trace organic micropollutants – molecules like pharmaceuticals and personal care chemicals – as well as pathogenic microorganisms that standard treatment doesn’t fully eliminate.
2. Ozonation
The next step is filtration followed by ozonation using Xylem’s WEDECO SMO Evo system. Ozone, a highly reactive form of oxygen, breaks down complex organic molecules that are otherwise persistent. In the Schweinfurt system, ozonation eliminates more than 80% of key indicator chemicals defined under the revised EU Urban Wastewater Treatment Directive. Additionally, the process inactivates over 99% of bacteria and viruses, adding a robust safety barrier early in the treatment chain.
3. Biologically Activated Carbon (BAC) filtration
Following ozonation, the water passes through filters populated with specialized microbes and activated carbon. These microbes biologically degrade the ozone-oxidized by-products, while the carbon adsorbs remaining organic micropollutants. This two-fold approach – biodegradation plus adsorption – further lowers the concentration of lingering contaminants.
4. Nanofiltration
Next is nanofiltration using a high-pressure membrane (DOW-Filmtec NF 4040). Nanofiltration removes dissolved salts, a wide range of micropollutants, and microbial contaminants. Unlike reverse osmosis, common in potable reuse systems but energy-intensive and challenging to operate due to concentrate disposal issues, nanofiltration strikes a favourable balance of performance and energy efficiency. This makes it ideal for the scale of Reuse Brew.
5. Advanced oxidation
The final safety barrier is advanced oxidation, implemented through Xylem’s MiPro Advanced Oxidation Process. This combines hydrogen peroxide and ultraviolet (UV) irradiation to generate hydroxyl radicals – powerful oxidants that can eliminate residual contaminants. In the Reuse Brew process, a hydrogen peroxide concentration of 1 mg/L (parts per million) and a UV dose of approximately 3000 mJ/cm² guarantee another 90% removal of residual chemicals and 99.9999% pathogen inactivation (6-log removal).
Beyond beer: the broader importance of water reuse
Throughout the duration of the Reuse Brew project around 6,000 litres of wastewater water will be treated to produce approximately 4,000 litres of high-quality water and brew 1,500 – 1,800 litres of beer. But Reuse Brew is more than a scientific demonstration and a nice beverage. It’s a conversation starter – a way to make water reuse tangible and relatable. As water scarcity becomes more acute, reuse will play a vital role in future water systems. Technologies proven in projects like Reuse Brew can be scaled for irrigation, industrial use, and potable reuse, helping reduce pressure on groundwater and surface water sources.
Raise a glass to the future
The Reuse Brew project demonstrates that wastewater is not waste. It is an important resource waiting to be transformed into exceptionally pure, safe drinking water. By combining cutting-edge engineering, rigorous science, and creative storytelling, this initiative helps shift perceptions and pave the way for broader adoption of water reuse technologies.
In a world where water scarcity isn’t just a distant threat, but a present-day reality, projects like Reuse Brew show how high-quality reclaimed water can open new pathways to strengthening water security for generations to come.
Dr. Uwe Hübner, Senior Sales & Process Engineer, Water Reuse & AOP, Xylem Water Solutions
Prof. Dr. Jörg E. Drewes, Chair of Urban Water Systems Engineering, Technical University of Munich
Prof. Dr. Thomas Becker, Chair of Brewing and Beverage Technology, Technical University of Munich