AIX-Net-WWR - We drive the reuse of wastewater!
AIX-Net-WWR, the Aachen Network for Waste Water Reuse, wants to “give wastewater a new lease of life” – not just once, but again and again!
Results from the second alliance and strategy meeting in November 2025 of the Aachen Network for Waste Water Reuse
1. introduction
The water industry is undergoing profound change. Stricter legal requirements, rising expectations of water protection and increasing regional water scarcity require new technological approaches. At the same time, existing centralised wastewater infrastructures are reaching their limits in terms of capacity, energy requirements and the removal of micropollutants.
The AIX-Net-WWR - Aachen Network for Waste Water Reuse therefore aims to develop modular semi-decentralised systems for wastewater reuse, close local water and energy cycles and at the same time reliably meet the water quality requirements for discharge(EU Municipal Wastewater Directive (KARL)) or reuse (e.g. EU Directive 2006/7/EC for bathing water, EU Regulation 2020/741 and DWA-M1200 for irrigation).
Semi-decentralised systems connect several buildings with a common treatment plant at district level. The close proximity of wastewater generation, treatment and utilisation means that water, heat and recyclable materials can be recovered or used directly on site. Centralised wastewater treatment plants can also be relieved and the resilience of the water infrastructure increased.
A particular concern of the network with the new technology is to involve local utilities and waste disposal companies as future operators of the plants wherever possible. This approach can prevent the new wastewater reuse technology from being seen as competition to the existing infrastructure. This in turn helps to secure the financing of the municipalities' supply mandate.
Decentralised water supply systems also increase the crisis resilience of the critical infrastructure because they reduce dependencies on central networks and individual failure points. In the event of power outages, line breaks or sabotage, local supply units remain functional and can maintain or restore the basic supply more quickly. At the same time, they enable flexible scaling and redundancy so that regions remain more stable and capable of acting even in the event of large-scale disruptions.
The systems are designed to
- treat domestic wastewater for reuse
- supply entire neighbourhoodsnew or existing buildings
- make the entire wastewater stream available for reuse
- heat energy recovery
- utilise the existing wastewater pipes
- to involve local supply and disposal companies as operators, to be operated economically through standardisation
- improve the crisis resilience of critical infrastructure
1.1 The network
AIX-Net-WWR brings together 11 companies, one start-up and five research institutions, supported by over 30 associated partners such as industrial companies, water suppliers and wastewater disposal companies, as well as other organisations from the construction and environmental sectors. The alliance is open to further associated partners who wish to actively support the project. The common goal is to make AIX-Net-WWR a leading global network for water reuse and to give wastewater a new lease of life.
Scenario 1 - Discharge according to KARL
As required by KARL, wastewater is treated according to the 4th treatment stage for regions without acute water scarcity and without the possibility of connection to a municipal wastewater treatment plant. (see Fig. 4)
Scenario 2 - Reuse as irrigation water
For areas with local water shortages but an existing drinking water supply, Class A quality is achieved for agricultural irrigation in accordance with EU Regulation 2020/741. (see Fig. 5)
Scenario 3 - Reuse as process water
In the event of an existing water shortage, the water is treated to service water quality according to NSF/ANSI 350-2014 Class C for use in toilet flushing or washing machines, for example. This application can only be realised in new buildings. (see Fig. 6)
Scenario 4 - Reuse as drinking water
For regions with pronounced water shortages, the wastewater is treated in a multi-stage process chain to drinking water quality in accordance with the Drinking Water Ordinance. Such a system can be used in both new and existing buildings. (see Fig. 7)
3. the joint projects: Progress and current status
The five joint projects form the technological basis of the overall system consisting of a membrane bioreactor with powdered activated carbon dosing, biohybrid adsorber granulate, non-thermal plasma oxidation, nanofiltration and flow-capacity deionisation, linked by innovative control and monitoring concepts to ensure water quality.
3.1 AIX-WWR - Development of the preparation system
In AIX-WWR, a demonstrator is being developed for the treatment of 20 m³/d of domestic wastewater. The wastewater is fed from a storage tank and initially pre-treated in a screen with a 1 mm screen hole width (Figure 9). It then flows into the membrane bioreactor, which consists of a selector, denitrification, nitrification and ultrafiltration (UF). The selector is used to promote floc-forming microorganisms and inhibit filamentous microorganisms in order to optimise the biodegradation performance. In order to achieve the target of 80% trace substance removal, powdered activated carbon is dosed into the bioreactor before the wastewater is filtered through a UF membrane with a pore size of 0.02 µm. This treatment is expected to ensure that the permeate fulfils the requirements, including the elimination of trace substances according to KARL. Commissioning of the demonstrator is planned for February 2026.
3.2 AIX-SOLVED - Biohybrid adsorber granulate
AIX-SOLVED produces a biofunctionalised adsorber granulate with the aim of removing trace substances and heavy metals such as copper, zinc and chromium. The biofunctionalised granulate consists of an inorganic carrier material to which enzymes are applied with the help of anchor peptides (Figure 10a). The enzymes are produced from plants and then fixed to the granulate with an anchor peptide. The materials have already been characterised and suitable enzymes and peptides have been selected. A prototype of a batch reactor (Figure 10b) was built to test the granulate in real operation. This will be installed in the demonstrator in 2026.
3.3 AIX-OXI - Non-thermal plasma oxidation
In AIX-OXI, a non-thermal plasma process (NTP) is used to generate reactive species such as OH radicals, hydrogen peroxide and ozone for trace substance degradation and sterilisation. The process is based on a dielectric barrier discharge. The plasma gas is introduced into the water in fine bubbles using a new type of perforated electrode. A 12-litre laboratory pilot has already been tested and initial degradation tests were successful (Figure 11). Based on this, two prototypes with 10 m³/d each are being developed, which will be operated in semi-continuous and continuous mode respectively. Both prototypes will be integrated into the AIX WWR demonstrator in order to treat a partial flow.
3.4 AIX-WATCH - Monitoring and validation
AIX-WATCH is focussing on monitoring water quality and developing a new type of fluorescence probe. The fluorescence probe is designed to enable more sensitive online analysis than conventional UV-ViS probes for sum parameters such as DOC. Among other things, a ColiMinder is used for online microbiological analysis, while standard parameters such as TOC, COD, BOD, NO₃-N and NO₂-N can be recorded online using specially equipped automatic samplers and corresponding reserve samples can be formed in the event of anomalies. One aim is to detect correlations between standard parameters and the data from the online probes in order to reduce the effort required for manual laboratory analyses and thus ensure cost-effective, continuous online monitoring of water quality. By integrating all measurement data from the demonstrator into a cloud application, it should also be possible to monitor the entire system remotely. All systems analysed in AIX-WATCH will be integrated into the demonstrator in 2026.
3.5 AIX-DEZI - Nanofiltration and flow-capacitive deionisation
AIX-DEZI specialises in the treatment of industrial wastewater, in particular the desalination of brackish and seawater and the removal of perfluorinated and polyfluorinated compounds (PFAS). Flow-electrode capacitive deionisation(FCDI) is used for desalination. In parallel, UF membranes are functionalised into nanofiltration membranes (NF) by means of layer-by-layer coating, which allows the pore size and charge of the membrane to be adjusted to different waters. Efficient PFAS separation from landfill leachate has already been demonstrated experimentally with real waters
As the project progresses, the technologies will be scaled up to investigate the possible applications with real water and the interconnection of the technologies with each other and the interaction of the AIX-Net process will also be investigated.
4 Vision and outlook
In order to develop an economical system series for semi-decentralised systems, series production of the modular individual technologies is being sought. In addition, operator models for the integration of supply and disposal companies are being developed.
SAVE THE DATE: Our final meeting will take place on 15 December 2026 in Aachen and we would be delighted to welcome you there. If you are interested, please register here: aixnetwwr@~@intewa.de
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Coordination of the alliance: INTEWA GmbH
Authors: Oliver Ringelstein, INTEWA GmbH, Dr Olga Murujew, INTEWA GmbH
E-mail: aixnetwwr@~@intewa.de
Website: https://www.aix-net-wwr.com