Aachen network for wastewater reuse wants to give water a new lease of life
AIX-Net-WWR, the “Aachen Network for Waste Water Reuse,” is working toward the vision of a complete recycling loop for wastewater.
After a selection process lasting several years, the Aachen-based business and research network AIX-Net-WWR was able to prevail alongside numerous other applications and began its work on 1 January 2024 to develop innovative solutions for the reuse of wastewater over the next three years. The approximately €12 million project, with a focus on the Aachen city region, is funded by the RUBIN ("Regional Entrepreneurial Alliances for Innovation") programme under the "Innovation & Structural Change" heading of the Federal Ministry of Education and Research (BMBF)
The environment
Around the world, climate change with record heatwaves and droughts is increasingly leading to regional water shortages on the one hand and heavy rainfall events with associated flooding on the other. After many years of intensive negotiations, all United Nations member states have committed to changing the global economy in a climate-friendly way. The Green Deal should lead to investments totalling at least 1 trillion euros in the European Union by 2050.
The goals and recommendations for action are described in the United Nations' 17 Sustainable Development Goals (SDGs). Nine of these goals alone relate to the topic of "water". Sustainable water management is therefore a key prerequisite for the implementation and achievement of a large part of the Sustainable Development Goals. At the same time, ESG (Environmental Social Governance) investment criteria have been recognised on the financial market. This demonstrates that only sustainable entrepreneurship can be economically viable in the future. The new AIX-Net-WWR alliance is taking action in the context of these pioneering framework conditions.
Current situation and goals
In view of increasing water scarcity and rising energy prices, sustainable water management is essential. Most cities today have a centralised water supply and wastewater disposal system. However, this has some disadvantages, such as decreasing water supplies with increasing water demand and the loss of resources and energy, especially in the form of water and heat (approx. 55 m³ water/person/year and approx. 550 kWh/person/year), for direct recycling at the point of wastewater generation. In many central wastewater treatment plants, the wastewater is also insufficiently treated for possible reuse, depending on the size of the connection, so that the remaining substances contribute to increasing water pollution. In the AIX-Net-WWR city of the future, there should be standardised, semi-decentralised wastewater reuse systems at district level with innovative individual technologies that address the problems mentioned. Semi-decentralised means that several buildings are connected to one system. The advantages of semi-decentralised systems lie in particular in the close spatial linking of wastewater generation and treatment. This enables the direct reuse and utilisation of the treated water and the energy present in the wastewater at the place where the wastewater is produced, and this is optimised both ecologically and economically.
When designing the semi-decentralised treatment plants, AIX-Net-WWR set itself the following goals:
- the possibility of treating wastewater to produce different qualities of water, such as bathing water, irrigation water, process water, sanitary water and drinking water
- the use of the systems in the construction of new residential areas but also for the conversion of existing structures with the involvement of local supply and disposal companies
- a modular and scalable design
- the cost-effectiveness of the systems within a few years by saving the core resources of water and energy and standardising the systems
The innovative individual technologies within the standardised systems should also be able to treat industrial and commercial wastewater, thus enabling individualised solution models.
A particular concern is the early involvement of local utilities and waste disposal companies as future operators of the systems in order to fulfil the economic interests of sustainable water supply.
The network and its partners
AIX-Net-WWR consists of 11 companies, one start-up and five research institutions from the Aachen region (Figure 2). The partners combine their expertise in the fields of water treatment, environmental technology and digital control systems.
The network is also supported by numerous industrial companies and utilities (Figure 3). The network is very interested in further associated partners and supporters. If you are interested, please send an e-mail to: aixnetwwr@intewa.de
AIX-WWR
In the 1st joint project AIX-WWR "(Semi-) decentralised wastewater treatment system", a demonstrator in container form for the treatment of domestic wastewater is being developed with the aim of achieving the most complete recycling possible. A core component of the demonstrator is an innovative, energy-efficient membrane bioreactor (MBR), in which wastewater is first treated biologically and then with an ultrafiltration membrane. In addition, powdered activated carbon (PAC) is dosed to remove trace substances, e.g. pharmaceutical residues and household chemicals.
In addition to wastewater treatment, heat recovery from wastewater is also part of the project. There is currently an exchange with a regional water supplier in order to enable the practical realisation of the theoretical concept.
The demonstrator will treat 20 m³ of domestic wastewater per day, which corresponds to approx. 135 PE. For this purpose, it will be installed, tested and further developed locally at the Aachen Test Institute for Wastewater Technology during the project period.
In the first year of the project, the concept of the MBR was worked out and process flow diagrams and design drawings were created (Figure 4). In the demonstrator setup, one container will contain the MBR, while two further containers will contain the measurement technology and additional treatment stages (see AIX-SOLVED and AIX-OXI below) to achieve drinking water quality.
The containers were delivered in January 2025 and are currently being prepared for operation. Commissioning is planned for the second quarter of 2025.
AIX-SOLVED
The contamination of wastewater from private households and industry with heavy metals and dissolved trace substances, such as additives and pharmaceuticals, is steadily increasing in Europe. As these dissolved substances are difficult or impossible to biodegrade and accumulate in the environment with unknown effects, environmental regulations for wastewater treatment and water reuse in the EU are increasing. However, these trace substances do not sediment and pass through conventional filter systems due to their size in the nanometre and micrometre range. In addition, their low bioavailability means that they are hardly biodegradable in wastewater treatment plants, making it increasingly difficult to comply with environmental regulations in the EU.
In the 2nd joint project AIX-SOLVED "Advanced treatment stages for the removal of dissolved substances", a purification process is being developed in which iron oxide and iron hydroxide-based adsorber granulates are biofunctionalised with enzymes, whereby dissolved substances are adsorbed and/or degraded. For the adsorber granulates, known granulates and a newly developed adsorber granulate, which utilises bauxite residue as a raw material, are used. Bauxite residue is a waste product of aluminium production and is therefore available in large quantities worldwide. As part of the project, a prototype is being developed and tested both on a laboratory scale and in pilot tests on the demonstrator using three types of substance that are common in wastewater:
- Heavy metals: zinc, copper, chromium, cadmium and nickel, which are present in wastewater due to domestic installations, removal of metal roofs and gutters and use of detergents and cleaning agents.
- Additives: such as the UV-B filter octocrylene in sun creams, the corrosion inhibitor 1H-benzotriazole and the plasticiser bisphenol A.
- Medicines: analgesics (such as diclofenac), antiepileptic drugs (such as carbamazepine, gabapentin and primidone), antibiotics (such as clarithromycin, sulfamethoxazole, metronidazole and trimethoprim)
A new type of filter unit based on a screen crusher is being developed for the optimum use of the coated granulate in decentralised water treatment. The first granules were produced and characterised in the first year of the project. This was followed by the determination of the diameter of the granulate to be used and the selection of the peptides and enzymes. In addition, the concept of the filter system with a sieve screen was defined.
AIX-OXI
The 3rd joint project AIX-OXI "Oxidative treatment using non-thermal plasmas" is developing an innovative plasma technology for the energy-efficient removal of organic trace substances from wastewater. The aim is the decomposition of poorly degradable compounds through plasma oxidation. The process is based on the generation of reactive oxygen and hydroxyl radicals, which enable the effective elimination of trace substances. The aim of the development is to create two reactor types: a continuous flow reactor and a semi-continuous reactor with a treatment volume of 10m3/d. A central component of the system is a new type of electrode for generating the non-thermal plasma, which is crucial for the efficiency of the purification process.
In the first year of the project, several electrodes were developed for testing, a pilot-scale plasma source was built (Figure 6) and the concept and a 3D drawing for the upscaled prototype were created. Current work is focusing on characterising the plasma and testing the mechanical stability of the electrodes.
AIX-WATCH
The 4th joint project AIX-WATCH "Monitoring and control technology incl. development of a validation methodology" focusses on the development of innovative technologies for monitoring and ensuring the chemical and hygienic quality of treated wastewater for reuse. The focus is on the development of new measurement, control and validation methods for decentralised water reuse systems.
Online monitoring reduces the need for on-site specialists and simplifies the operation of decentralised wastewater systems. The new measurement technology provides quick results on water quality without the need for lengthy laboratory analyses.
An important technical component is 2D fluorescence spectroscopy, which is used for precise inline analysis of water quality parameters such as TOC, BOD, COD and trace substances. A robust 2D fluorescence probe (Figure 7) is being developed for this purpose, which enables continuous real-time monitoring. This is supplemented by a cloud-based, data-driven assistance system that uses machine learning methods to detect anomalies and enable predictive analyses.
Furthermore, innovative measurement and sampling control systems are being developed to ensure automated monitoring of wastewater flows. Methods for validating WWR plants using online measurements are also part of the project. The combination of sensor technology, data analysis and automation is intended to improve quality assurance and process optimisation in wastewater reuse plants. In the first year of the project, the first measuring devices were procured and put into operation, and some of the test and analysis planning was carried out. The cloud architecture and data acquisition software were also created.
AIX-DEZI
The 5th joint project AIX-DEZI "Decentralised industrial application" focuses on the development of novel technologies for the treatment of municipal and industrial wastewater. At the DWI - Leibniz Institute for Interactive Materials, these technologies are being tested on a small laboratory scale and expanded to a larger pilot scale in cooperation with the company SIMA-tec.
The focus here is on two aspects of municipal water treatment: the desalination of brackish and seawater and the removal of PFAS from wastewater. PFAS are persistent carbon compounds that are found in many everyday products and are difficult to break down. Their detection in wastewater is often difficult as they are only present in very small concentrations. The RWTH Institute of Urban Water Management is responsible for analysing PFAS and salts as part of this project.
Two technologies are to be used for purification: Nanofiltration (NF) membrane technology and flow capacitive deionisation (FCDI). NF membrane technology uses membranes with pore sizes of 1-10 nanometres to filter out impurities. As part of the project, membranes are to be coated in order to reduce the size of the pores so that PFAS, for example, can be removed. Figure 8 shows a) hollow fibre membranes, b) their coating and c) a membrane module. The first successful coatings and the target density for PFAS retention have been achieved. Trials with real water are currently taking place and the first models for a scale-up are being created. FCDI uses an electric field to desalinate water by adsorbing charged substances such as salts on carbon particles. Initial successes in the desalination of brackish water were achieved and a pilot model was created with SIMA-tec. The experimental results are incorporated into a simulation model that enables predictions to be made about the purification performance under various operating parameters.
The first AIX-Net-WWR alliance meeting took place on 6 November 2024 at the digitalHUB in Aachen. During the event, the partners discussed market conditions, technology paths and operator models in order to optimise the marketing of the developed solutions. Other key topics included implementation and success planning as well as overcoming the shortage of skilled labour.
In interactive world cafés, the partners presented their technologies, discussed challenges such as cost-effectiveness, sustainability and longevity of the systems and promoted dialogue with associated partners.
The alliance is open to further associated partners who want to actively support the project with the common goal of making AIX-Net-WWR a leading network for water reuse worldwide and giving wastewater a new life. We look forward to your participation! Our next alliance meeting will take place on 6 November 2025 in Aachen and we would be delighted to welcome you then. If you are interested, please register here: aixnetwwr@intewa.de.
Summary and outlook
This technical article presents the Aachen-based network AIX-Net-WWR, which aims to achieve sustainable wastewater recycling. Funded by the BMBF, the alliance is developing semi-decentralised wastewater treatment systems that reuse water and energy directly on site.
The network's five joint projects focus on different technologies: AIX-WWR is developing a demonstrator with a membrane bioreactor for biological purification and heat recovery, while AIX-SOLVED is researching enzyme-coated adsorber granules for the removal of heavy metals and trace substances. AIX-OXI focuses on plasma technology for oxidative treatment, AIX-WATCH on digital monitoring methods and AIX-DEZI on innovative processes for industrial wastewater treatment.
Looking ahead, the developed technologies will be further optimised, tested in pilot plants and evaluated economically. The alliance plans to establish itself as a leading competence centre for water reuse and invites other associated partners to join the initiative. The next alliance meeting on 6 November 2025 will provide an opportunity for professional exchange and networking.
Authors
Dr Olga Murujew, Project Manager AIX-Net-WWR
Oliver Ringelstein, AIX-Net-WWR Alliance Coordinator
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Status: 27.2.25
Further information:
Basic knowledge of water treatment: wiki.intewa.net/index.php/Hauptseite
Website with information on the project: www.aix-net-wwr.com/de/home
Note: Changes to the technical article are only permitted with the express authorisation of the author!