HypoWave+ – Implementation of a hydroponic system as a sustainable innovation for resource-efficient agricultural water reuse

Challenges and background

Climate change, urbanization and the pollution of conventional water resources will in the coming decades lead to rising regional competition over the use of the increasingly scarce water resources. At the same time, there is a growing demand for regional vegetables that are produced in a resource-efficient way. For irrigation in agriculture, environmentally friendly water recycling can serve to increase the water supply. So far, there had been no large-scale implementation of the piloted HypoWave concept. This task has now being addressed in the follow-up project HypoWave+, which was coordinated by the TU Braunschweig.

Research approach

The aim of the transdisciplinary research network was to establish a new form of regional vegetable production. Based on the results of the HypoWave research project, farmers in the Gifhorn region decided to establish a company that produces hydroponically grown vegetables. HypoWave+ accompanied this project scientifically and investigated open questions in the areas of water treatment, vegetable production, intelligent process control, quality management and institutional arrangements. The aim was to further develop the marketability of hydroponically produced vegetables by means of environmentally friendly water recycling with the aim of applying it at other locations as well.

Within the framework of HypoWave+, Fraunhofer IGB has been working on the digitalization of the established processes. To this end, the team has been coordinating the work on integrated data acquisition and control of the water treatment and the greenhouse production, as well as on setting up and operating the infrastructure required for data acquisition and processing. In addition, the IGB coordinated the detection of (plant)-pathogenic microorganisms and viruses in the treated water and, together with other partners and actors on site, contributed its technical expertise on questions of acceptance and quality of the new process chain as well as on risk management.

Digitalization

The networking of water management and crop production system elements—a challenge due to the proprietary control logic of the individual components—was successfully implemented by Fraunhofer IGB. In addition, the extent to which artificial intelligence (artificial neural networks) can be used to optimize operations was also investigated. The work on integrating such AI elements is important in order to harness the potential of this rapidly developing technology for the requirements of water reuse. This can increase the efficiency of the resources used on the one hand and reduce the risks of closing the cycle on the other. This lays the foundation for the spread of water reuse in Germany and for the exportability of solutions developed in Germany.

Integrated quality management

As part of the integrated quality management system, Fraunhofer IGB has focused in particular on risk management. For example, a risk management plan (RMP) was developed in close cooperation with the partners involved in the implementation of water reuse in Weißenberge, which formed the basis for the successful application to the lower water authority in Gifhorn. This made the exemplary implementation of water reuse in Weißenberge possible in the first place. In addition, an integrated quality management concept was developed here in collaboration with ISOE, which was published and is thus also available for other applications [1, 2].

It was found that the risks to humans and the environment posed by water reuse in Weißenberge can be classified as low overall with the existing process chain. This was also confirmed by water and product analyses. Chemical and microbial risks were successfully addressed through water treatment and multiple barriers.

With regard to phytopathogenic microorganisms, exemplary studies were conducted at Fraunhofer IGB, which will allow for better classification and minimization of corresponding risks for water reuse in hydroponic systems in the future. While human pathogenic microorganisms are the focus in the context of water reuse, information on the introduction of plant pathogenic microorganisms, which can cause financial losses for farmers in particular, is very limited. Our investigations have shown that under Hypowave+ conditions, there is only a very low risk of damage from plant pathogenic microorganisms in treated water. Since the investigations used in the project are very cost-intensive, further methods were developed to simplify the detection of certain plant-pathogenic microorganisms and make it more accessible. This should provide a better data basis in the future, as measurability has been simplified [3].

Publications

1. Winker, Martina/Marc Beckett/Thomas Dockhorn/Nico Domurath/Tim Gebhardt/Jorn Germer/Heide Kerber/ Christian Lampe/Marius Mohr/Stefan Pieper/Michaela Rohrbach/Engelbert Schramm (2025): Integrated Quality Management for Hydroponic Water Reuse – A Dual-Objective Approach. Water Reuse. https://doi.org/10.2166/wrd.2025.033
2. Beckett, Marc/Marius Mohr/Martina Winker/Michaela Rohrbach/Antje Schwarzer/Tim Gebhardt/Thomas Dockhorn (2025): A critical assessment of the applicability of EU regulation 2020/741 for the development of a risk management plan for hydroponic water reuse. Water Reuse. https://doi.org/10.2166/wrd.2025.032
3. Kriem, Lukas Simon, King, Neil, Niemann, Sinja, Vainshtein, Yevhen, Sonntag, Mirko (2025): Molecular Identification of Human and Plant Pathogens in Municipal Domestic Wastewater for Hydroponic System Applications, International Journal of Microbiology, 2025, 6958575, 14 pages. https://doi.org/10.1155/ijm/6958575

Molecular biological detection system for the detection of human pathogenic viruses in wastewater

In conventional wastewater systems, the treated wastewater is discharged into surface waters after passing through the treatment plant. There, it is further diluted and broken down by several natural processes: the inflow of fresh water, the effects of natural UV light, sedimentation, and biological degradation and filtration as it seeps into the groundwater.

In hydroponic systems with a shortened or closed water cycle, these natural dilution and degradation processes do not occur. The treated wastewater is used directly for irrigation. As a result, any remaining viruses cannot be diluted and could theoretically accumulate over several cycles. Human pathogenic viruses such as noroviruses, adenoviruses, or hepatitis A and hepatitis E viruses are particularly relevant, as they can be infectious even at very low concentrations and can directly contaminate edible plant parts via irrigation water.

Enrichment via ultrafiltration enables detection of even small virus quantities

Against this background, targeted and sensitive monitoring for such viruses in recirculating water is particularly important. A molecular biological detection system has therefore been developed at Fraunhofer IGB. First, the wastewater is concentrated by ultrafiltration: viruses are physically separated from large volumes of water by membranes with pore sizes in the nanometer range and highly enriched in a small volume. This pretreatment is crucial for making even very small amounts of viruses detectable. The concentrated material is then analyzed using quantitative real-time PCR (qPCR). Specific primers and probes enable the targeted, parallel, and quantitative detection of relevant human pathogenic viruses. The method is robust against typical inhibitors in wastewater and delivers reliable results within a few hours.

The combination of ultrafiltration and qPCR allows the microbiological safety of the reused irrigation water to be monitored regularly and reliably – a key prerequisite for the safe and sustainable operation of hydroponic production systems with wastewater reuse. At the same time, this form of water reuse makes a valuable contribution to conserving water resources, recycling nutrients, and significantly reducing the demand for fresh water in food production.