HypoWave – Water reuse in agriculture

Especially in regions where water is scarce, agricultural production often takes up most of the available water. Large quantities of this scarce resource evaporate or seep into the earth. The advantage of hydroponic plant production, which is also known to be remote from hydroponics in houseplants, is initially its low water consumption. The plants are supplied with a nutrient solution in plant containers without soil. No water seeps away and only little evaporates.

Objectives

In the “HypoWave” research project, an interdisciplinary team is investigating how the efficiency of this hydroponic plant production can be further increased by using municipal wastewater for irrigation. To this end, a pilot plant was built near Wolfsburg to reuse the specifically treated municipal wastewater for hydroponic production. There, the technical processes, plant production, the cost-effectiveness of the plant and the quality of the products produced are examined. In a second step, the potential and marketability of such production are investigated with the aid of case studies and possible actors of such systems are integrated into the research project via a stakeholder dialogue.  

Fraunhofer IGB was first involved in the work package “Piloting Wastewater Treatment”. Since 2017, IGB is coordinating the case studies and, together with project partners and local stakeholders, developing specific implementation concepts for the entire system that are adapted to local conditions.

Piloting

As part of the pilot project for the overall system, the IGB is operating an EGSB-R test system developed by its partner ACS-Umwelttechnik GmbH & Co. KG (Expanded Granular Sludge Bed) for the anaerobic pre-treatment of municipal wastewater. Here, organic impurities are converted into the energy source biogas, while the nutrients, which are necessary as fertilizer for the plants in the hydroponic system, are preserved.

Furthermore, Fraunhofer IGB has developed a comprehensive control system for the pilot plant, which enables the individual modules of wastewater treatment and plant production to communicate with each other. The control of Fraunhofer IGB is also the interface to the modelling and target value specification of the artificial neural networks of the partner aquatune - Dr. Gebhardt & Co GmbH.

Case studies

Case studies at four different locations in Germany, Belgium and Portugal are used to determine how the concept can be implemented. These case studies are being developed by transdisciplinary teams in cooperation with local stakeholders. The aim is to identify beneficial and limiting factors for the use of treated wastewater in the hydroponic system and possible site-specific applications of the concept. This should create the basis for the next steps of a possible realization at the sites being investigated.

Two case studies were completed in 2018 and the results are now available in the form of a brochure. In the district of Gifhorn (Lower Saxony), the effluent of a sewage pond for the cultivation of lettuce was investigated. This allows the concentration of nutrients in the effluent to be reduced to such an extent that connection to a larger sewage treatment plant becomes unnecessary. In Raeren in the Euregio (the border region of Belgium, the Netherlands and Germany), a wastewater treatment plant including a greenhouse for the cultivation of cut flowers was designed for an area whose wastewater flows untreated into a body of water. A short rotation plantation will also use the remaining nutrients for biomass production.

Summary

With the use of treated wastewater, two objectives can be achieved: the purification of wastewater, especially regarding nitrogen and phosphorus elimination, and optimal plant growth through good water and nutrient supply. Adequate quality management is necessary to ensure a good supply of micronutrients to the plants and to comply with microbiological hygiene requirements. For example, irrigation water should be sanitized using suitable disinfection measures, e.g. UV, ozone or membrane filtration.

Opportunity windows for the implementation of the HypoWave concept are situations in rural areas susceptible to water scarcity and where the wastewater infrastructure has to be adapted or (re)developed. Water reuse can also be integrated into wastewater treatment plants that are planning a fourth treatment stage, and is suitable in principle for city expansions and new district buildings. In this way, conflicts over the use of water resources, which are becoming more acute due to climate change and overexploitation, can be defused.

Literature

[1] Mohr, M., Schramm, E., Ebert, B., Germer, J., Bürgow, G., (2019) Nutzung des Ablaufs einer Teichkläranlage zum Anbau von Gemüse im hydroponischen System im Landkreis Gifhorn – Ergebnisse einer Fallstudie. Zbl. Geol. Paläont. Teil I, Jg. 2019, H. 1: 65–72

[2] Drewes, J., Becker, D., Jungfer, C., Krömer, K., Mohr, M., Nahrstedt, A., Schramm, E., Winker, M., Zimmermann, M. (2018) Mindestanforderungen an eine Wasserwiederverwendung: Hinweise aus Sicht der WavE-Forschungsprojekte des Bundesministeriums für Bildung und Forschung (BMBF). gwf Wasser Abwasser 12/2018: 50-59

[3] Drewes, J.; Schramm, E.; Ebert, B.; Mohr, M.; Beckett, M.; Krömer, K.; Jungfer, C. (2019) Potenziale und Strategien zur Überwindung von Hemmnissen für die Implementierung von Wasserwiederverwendungsansätzen in Deutschland, Korrespondenz Abwasser, Abfall 12/2019

[4] Mohr, M.; Günkel-Lange, T.; Fischer, M.; Germer, J.; Winker, M.; Bürgow, G. (2019) Water reuse in hydroponic systems: results from four European feasibility studies, Vortrag auf der 12^th IWA International Conference on Water Reclamation and Reuse, 16. Juni 2019, Berlin