Water management

^{Web special Fraunhofer magazine 2.2024}

Pessimists view the glass as half empty: According to a study by the GFZ German Research Centre for Geosciences, Germany lost 750 million metric tons of water a year from 2002 to 2022 through factors such as declining soil moisture, decreasing groundwater, melting glaciers, and generally sinking water tables. The country’s total stores of water shrank by 15.2 cubic kilometers over this period. That’s almost half of the total water consumed by industry, agriculture, and private households across the whole of Germany in a year.

Optimists look to the stores of water still present in Germany. Groundwater levels rose nationwide in 2023, a relatively wet year, and 2024 has turned out to be fairly damp as well so far. Per capita drinking water use has declined significantly, from 147 liters a day in 1990 to 121 in 2023. “There is a growing public awareness of water management,” says Dr. Marius Mohr, head of the Water Technologies, Resource Recovery and Scale-up innovation field at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart. And with good reason, he says, in light of the increase in extreme weather events such as torrential rains and droughts. Although spring 2024 felt very different, he notes, “We will experience periods of drought in Germany in the foreseeable future much like those Spain already has today.”

Given these forecasts, keeping the glass at least half full will require big changes in how people use water. The German federal government’s 2023 National Water Strategy calls for sustainable use of water resources along with improved protection for natural water stores to guard against contamination with chemicals and microplastics. This will require significant efforts across all sectors: industry, agriculture, public water supply. There are currently eleven Fraunhofer institutes participating in the Fraunhofer Water Systems Alliance (SysWasser), all contributing their expertise to make water infrastructure systems more sustainable and more resilient. The ultimate aim is to move water and wastewater management in the direction of a circular economy and to support the agriculture sector in adjusting to new climate conditions.

Private households and municipalities: greater digitalization

The research sector, government, and industry all hope the digital transformation will provide powerful leverage in the world of water management. For example, the InDigWa project was launched in the fall of 2023 within the Morgenstadt (City of the Future) Innovation Network, a network of Fraunhofer institutes, municipalities, and businesses. As part of the project, the Fraunhofer Institute for Industrial Engineering IAO and the Fraunhofer Institute for Systems and Innovation Research ISI and Fraunhofer IGB plan to collect data on the entire drinking water cycle, from well to use and disposal.
Smart interconnectivity: “Industry and medium-sized businesses and the various stakeholders in the municipal water supply and wastewater disposal space have already developed a lot of individual innovations,” explains project manager Susanne Liane Buck from Fraunhofer IAO. “Our approach is to link these isolated solutions together into a single system and incorporate consumers as well in order to enhance the efficiency of the drinking water supply on the basis of collected data.”
The project calls for existing approaches such as low-flow showers and separate cycles for drinking water and “gray” water, meaning wastewater with moderate levels of contaminants, to be installed and tested in selected homes in a residential development in Bremen. For outdoor areas, there are plans for smart rainwater management to improve the efficiency of managing water supply and disposal systems, including during periods of drought and heavy rain. An innovative watering system for green space in the immediate area is intended to reduce the use of drinking water. Buck explains: “Our goal is to create a template for holistic water management that works in both new construction and existing neighborhoods.”

Twelve project partners, from the local water supplier and a housing developer to building technology and sensor companies and the wastewater disposal provider, are all on board in the interdisciplinary InDigWa project. Collecting data from private households is a challenge in light of privacy regulations, Buck says. After all, water use is a reflection of very private areas of people’s lives. But that window on what happens in the bathroom or kitchen is especially important in terms of further developing water-saving fixtures, for example. As a sociologist, Buck also knows that implementing innovations is never just about the technology itself. It also involves how willing people are to participate. And people in Germany, at least, are used to having top-quality water flow from the tap anytime they turn it on. That is why Mohr, for his part, takes a dim view of installing a second supply line inside buildings to provide “second-class water” for things like watering plants: “Once you increase the number of supply networks, the risk of improper connections rises, and that’s something we can’t have when it comes to drinking water. Even the slightest doubt about quality will be enough to turn people against using the drinking water that comes from the tap and send them running to buy water in plastic or glass bottles instead, which is even less sustainable.”

Projects like InDigWa can also help maintain water quality, however. “Increasingly long periods of heat also bring hygiene problems with them, such as a rising risk of Legionella bacteria in the water,” Buck explains. Continuous data collection is likely to make it possible for municipalities to monitor these factors more efficiently going forward.

For consumers, reports on their own consumption through an app or in other forms could also come as a wake-up call of sorts. After all, who among us knows how much water they use to shower in the morning or water the plants? Putting a figure to everyday usage like this and communicating it back to the consumer, whether that means a private individual or a company, is also the goal of the CrowdWater project funded by the German Federal Ministry for Economic Affairs and Climate Action (BMWK): Under the overall coordination of the Fraunhofer Institute for Applied Information Technology FIT, selected households and businesses are being equipped with smart meters and connected together to create a “living lab” that surveys water use in different sectors under real-world conditions.
“Our goal is to develop a decentralized data platform that can be used to measure water consumption in connection with specific events and then report it back to the consumer,” explains Dr. Marc Jentsch, an IT expert at Fraunhofer FIT. “After that, we plan to analyze the degree to which knowing their usage data changes people’s consumption habits and what incentives can spur sustainable water use.” Right now, Jentsch and his team are still looking for private households and manufacturing companies in the districts of Troisdorf, Kirchen (Sieg) and Hennef that are interested in participating in the living lab.

A sports school is already on board. To date, the school only has a single central meter for water consumption, so there are no details about how much water is being used for the swimming pool, showers, or watering the green space. Jentsch explains: “The school is hoping to use smart sensors to monitor water use by different areas in real time in the future.” As for the utility companies, they see huge potential for optimization in detecting leaks. “CrowdWater will help us significantly increase the density of the sensor network so leaks can be detected and stopped much faster,” Jentsch says. According to a study by the International Water Association, 346 million cubic meters of water is lost on the way to the consumer worldwide each day. The estimate for Germany is about 400 million cubic meters of water loss per year.

Agriculture: plants need water to grow

And those levels of loss are becoming less and less acceptable. After all, water is not only a vital resource in its own right, but also the foundation of food production. Sixty-nine percent of global water stores from groundwater and freshwater sources such as lakes and rivers are currently used for agriculture. But with the global population on the rise, the agriculture sector is expected to require as much as 50 percent more water by 2050 — even as water is increasingly in short supply due to climate change. Hydroponics, an approach that has been proposed to help with this dilemma, seems contradictory at first glance. Wouldn’t no longer growing plants in a soil substrate, but entirely in containers of water instead, actually increase water use?

No, says Marc Beckett, who works on development and implementation of sustainable water management and water use systems at Fraunhofer IGB. First, the water that supplies the plant with needed nutrients can be recycled, so it is enriched and reused over and over, while the water used for conventional agriculture seeps down into the soil or evaporates. That means the water doesn’t reach the plant, leading to higher water usage. “With hydroponics, we can cut water use by as much as 90 percent in these situations,” Beckett explains. Second, this form of cultivation also requires significantly less space, and because it does not depend on a specific location, it can be implemented even in urban environments, including through vertical farming.

Even more important when it comes to water conservation is the fact that hydroponics does not necessarily require the use of potable water. Wastewater can also be used, although this does, of course, require prior purification to remove germs and other harmful substances, whether using UV light or membrane or activated charcoal filtration. The HypoWave project and its successor HypoWave+, in both of which Fraunhofer IGB is involved, are working to develop solutions for hydroponic plant production, using municipal wastewater as a source of water. “Instead of removing nutrients like nitrogen, phosphorus, potassium, and calcium from the wastewater in an energy-intensive process, we leave that task to the plants,” Beckett explains. This approach is already being piloted in the Gifhorn district.

Tailored nutrition for plants

To that end, microbiologist Dr. Lukas Kriem is also planning to use waste to produce nutrient solutions for use in hydroponics: “Potassium, for example, is relatively easy to isolate from waste such as banana or potato peels. Reclaiming phosphate and nitrate from waste and wastewater is trickier. We’re working to develop suitable microbiological processes for that.”
This research approach was born of necessity: In a project at a refugee camp in the Sahara, scientists Beckett and Kriem were looking for a way to work with local stakeholders to further develop a hydroponic system so vegetables and herbs could also grow using hydroculture. In the NexusHub successor project, Fraunhofer IGB experimented with reusing animal and bone meal in hydroponic cultivation of vegetables and developed processes to create a hydroponic nutrient solution out of organic waste and use it to grow cilantro and kale. The energy needed to do this is to come from a solar array that is under development by the Fraunhofer Institute for Chemical Technology ICT. This will make this style of cultivation a sustainable possibility for even remote areas. The approach has already been implemented on a pilot scale in Kenya. “We aim to develop robust solutions that add value to even substances viewed as worthless in the past,” says Kriem.

Outside Africa, efficient and low-cost wastewater treatment is also growing more important. And not only because wastewater from households and industry contains pollutants such as microplastics and PFAS, or “forever chemicals,” which then get into the environment. In the ROOF WATER-FARM joint research project, the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT developed a method that can be used to treat “black” water – wastewater from toilets – on a decentralized basis and use it for vegetable production. In the SUSKULT project, the researchers are working on integrating water treatment facilities into agriculture. After all, from nutrients and water to heat and CO2, all of the resources needed for agriculture are present at a wastewater treatment plant. In the RoKKa project, Fraunhofer IGB is also working to convert treatment plants into wastewater biorefineries, including the use of residue and waste products: The researchers are using six pilot plants at the Erbach treatment plant in Baden-Württemberg to demonstrate the production of useful substances from sewage sludge. “The nitrogen that is present in high concentrations in the sewage water is especially interesting,” Mohr explains. Typically, nitrogen is produced from the air for use in fertilizers, an energy-intensive process. Separating the nitrogen early on could also reduce the harmful nitrous oxide emissions that typically arise when these substances are broken down.

Industry: recycling water, reclaiming raw materials

The research institutes that make up the Fraunhofer Water Systems Alliance (SysWasser) are also looking for innovative ways to process industrial and municipal wastewater streams so the water can be recycled in the manufacturing or agriculture sectors. This approach offers huge potential in terms of sustainable water management, as Germany’s manufacturing sector uses 4.5 billion cubic meters of water annually. At the same time that water conservation efforts are under way, there is also a growing awareness in industry that process water often contains chemicals or residual substances that could be reused in industrial applications. Wastewater from metalworking businesses can even be used as a source of costly raw materials such as silver and copper, which can be extracted and then recycled. This aspect makes reclamation an exciting prospect for both environmental and economic reasons.

What is in the water? To find out, the Fraunhofer Institute for Photonic Microsystems IPMS has developed an integration technology that can be used in the future to measure water parameters such as pH levels and nitrate, phosphate, and potassium concentrations continuously in parallel and in real time, all with just one sensor chip. Multiple ion-sensitive field-effect transistors (ISFETs) are built into the chip to determine the concentration of numerous ions in the water. Dr. Olaf R. Hild, head of the Chemical Sensors business unit at Fraunhofer IPMS, believes in the new technology: “This kind of measurement system unlocks new possibilities for applications in environmental analytics, agriculture and water management, and in the booming market for indoor farming applications.”

Researchers from the Fraunhofer Institute for Ceramic Technologies and Systems IKTS have set up a technology platform on the grounds of the Bitterfeld-Wolfen wastewater treatment plant to develop and test different treatment andbpurification methods to meet the needs of industrial customers. This sewage treatment plant is one of the largest in central Germany, and it processes wastewater from nearly 300 businesses located in a nearby chemical park. By combining advanced ceramic membranes with electrochemical, sonochemical, photocatalytic and biological processes, even process water with extremely heterogeneous compositions can be filtered and treated as required. The result is water and valuable materials, both ready for reuse.

This circular approach can make even sustainable products more sustainable. Take solar panels, for example: Scientists from the Fraunhofer Institute for Building Physics IBP and the Fraunhofer Institute for Solar Energy Systems ISE worked together with TU Berlin and Rena Technologies GmbH to create a model of water flows in a 5-gigawatt solar cell factory. Then, on that basis, they reviewed the introduction of various strategies for circular use of water. The researchers found that the amount of water used to produce the solar cells could be reduced by as much as 79 percent and wastewater by up to 84 percent, all with production technologies already available today. And that makes it easier to build new solar cell factories, even in locations with less water available.

“We have two approaches to recommend: reuse of low-contaminated wastewater (LCR) and what is called minimal liquid discharge (MLD), in which certain residual substances are reused for other purposes,” explains Peter Brailovsky from Fraunhofer ISE. This makes it possible to use residual etching solutions and other substances in cement production.

Repurposing used materials: In the near future, reprocessing of water needed for recycling lithium-ion batteries will be similarly important. The wastewater contains dissolved metal ions such as lithium, nickel, cobalt, copper, and aluminum − all critical materials for batter production that Germany typically has to import at high prices. At the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Spanish chemical engineer Dr. Cleis Santos is working in the MeGaBatt project to develop electrochemical technologies with which process water from the battery recycling process can be treated in ecofriendly, low-cost ways so the critical raw materials are also kept within the cycle. “We already know this works at the lab scale,” she explains. “But our goal is, by the time the project ends in 2028, to have built a pilot plant that demonstrates that this method also makes economic sense on a large scale.” Forecasts predict that the volume of batteries requiring recycling in Europe will increase from the current level of 50 kilotons to 2,100 kilotons in 2040. In the medium term, smart battery recycling could reduce dependence on battery material imports, at least to some degree. The MeGaBatt project is part of the BattFutur initiative, with which the German Federal Ministry of Education and Research (BMBF) is supporting next-generation battery researchers under the Forschungsfabrik Batterie (Battery Research Factory) umbrella project.

Electrochemical deionization of water, in which electrodes are used to remove ions from the water, is also interesting to other wastewater producers, such as hospitals, Santos says – and for desalination of seawater. More water from seawater? That’s an intriguing prospect. In fact, there are already 22,000 desalination plants around the world, producing both potable and process water from the oceans. But existing technologies – thermal desalination and pressing seawater through a membrane that can retain salt – require a lot of energy, which makes them expensive. Electrochemical desalination requires less energy, Santos notes. Mohr, from Fraunhofer IGB, sees an urgent need for development of new concepts on this point. Although it is unlikely that people in Germany will have to resort to drinking desalinated seawater anytime soon, he still points out: “Water is no longer a national issue. It should be viewed as a global challenge instead.” He has been working on the big issues relating to water for over 20 years now. Is there any risk that his research will become boring or routine? No, Mohr says: “To this day, it still feels like pioneering work.”