Borgmann Aquaponics Hydroponics
The UASB (treated aquaponics waste) effluent can be used after a targeted further processing as a source of nutrients for the hydroponics be used.
The idea: [Fish tank] → [Solid separator] → [UASB reactor]→[Remineralization component]→[Hydroponic loop]
- Nutrient content: After anaerobic treatment, the effluent still contains plenty of inorganic nutrients such as phosphate and Ammonium saltswhich are essential for plant growth.
- Project HypoWave: Researchers at Fraunhofer IGB are investigating HypoWave and its successors in the project HypoWave+, such as municipal wastewater, which is treated in UASB-like processes, can be treated in such a way that it serves as irrigation water for hydroponic plant breeding.
- Advantages: This concept combines water treatment with food production, saves drinking water and closes nutrient cycles. Pilot projects show that only a small additional addition of nutrients is necessary to achieve good plant growth.
- Challenges: A crucial requirement is the safe removal of pollutants (organic trace substances, heavy metals) and pathogenic germsto ensure product quality and food safety.
In Goddek's DAPS concept, the UASB reactor a mineralized effluate, which not yet directly suitable for hydroponics is. It contains:
| faction | problem |
|---|---|
| NH₄⁺ (instead of NO₃⁻) | Phytotoxic in high concentrations |
| Solved P (PO₄³⁻) | Often excess, risk of precipitation with Ca²⁺ |
| Organic residues | May contain pathogens/inhibitors |
| Missing elements | K, Ca, Mg, micronutrients often inadequate |
| pH unstable | Often >7.5 due to anaerobic processes |
This technique is very complex and includes (in telegram style) the following steps that are necessary to process and reuse the nutrients:
1 – Actual analysis (UASB effluate)
Entering the measured values:
NH4-N, NO3-N, PO4-P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, B, Mo pH, EC, Temperatur, Alkalinität (KH)
2 – Target profile (hydroponic target solution)
Deposit reference solutions (e.g. according to Hoagland, Resh, or system-specific):
e.g. NO3-N: 150–200 mg/L, K: 200 mg/L, Ca: 160 mg/L ...
3 – Delta calculation & processing steps
Calculate chemical process steps: Δ[ion] = Should - (Is × dilution factor)
Then depending on the delta (excerpt & examples):
| situation | measure |
|---|---|
| NH₄⁺ too high | Stripping (air input + pH↑) or nitrification stage |
| PO₄ too high | Precipitation with Ca(OH)₂ → Calculate struvite/CaP |
| K is missing | Dosage KNO₃ or K ₂SO₄ |
| Ca is missing | Ca(NO₃)₂ – but precipitation risk with PO₄ note! |
| Mg is missing | MgSO₄ |
| Fe missing | Chelate-Fe (EDTA/DTPA/EDDHA depending on pH) |
| pH incorrect | ENT₃ / KOH / Ca(OH)₂ |
4 – Precipitation risk check (critical !)
Ion product vs. solubility product (Ksp):
e.g. [Ca²⁺] × [PO₄³⁻]³ > Ksp → hydroxyapatite precipitates! [Ca²⁺] × [SO₄²⁻] > Ksp → CaSO₄ precipitation [Mg²⁺] × [NH₄⁺] × [PO₄³⁻] > Ksp → struvite (MgNH₄PO₄)
5 – Dosing calculation
Conversion of ion deficit → amount of chemicals:
Mass [g] = Δ[mg/L] × Volume [L] / (Purity × Molar fraction × 1000)
6 – Monitoring & Feedback
- Logging of measured values over time
- Trend analysis (e.g. K/Ca ratio drift)
- Critical Deviation Alarm
Comment: This brief overview already shows the technical effort required to save small amounts of nutrients. The size of the plant determines the necessity or usefulness of this process. Or the fertilizer price. The necessary nutrient full analysis quickly costs 100–200 € - per work-up cycle. Example prices here.
HypoWave+ is a research project funded by the Federal Ministry of Education and Research (BMBF) that scientifically supports the large-scale implementation of a process for water-saving plant breeding using treated municipal wastewater. It is the successor to the HypoWave pilot project.
The project deals with the large-scale realization of hydroponic vegetable cultivation in Gifhorn, in which treated wastewater serves as a complete replacement for drinking water and groundwater. The central goals are:
- Scientific support: The implementation of a real laboratory with a cultivation area of one hectare (600–700 tons of vegetables per year) will be scientifically monitored.
- Integrated quality management: Development of holistic quality management for the entire process chain, from water treatment to crop production and sales.
- Safe water treatment: Ensuring product safety through the development and establishment of a high-quality processing technique, including a novel activated carbon biofilter and a molecular biological detection system for viruses.
- Digital networking: Building a biointelligent overall system by networking water treatment and vegetable production using sensors and artificial neural networks.
- Market readiness: The findings are intended to make the process transferable to other locations as a viable, resource-efficient innovation.
Here are the most important links and other sources for the HypoWave+ project:
- Official project page at Fraunhofer IGB (German): https://www.igb.fraunhofer.de/de/referenzprojekte/hypowave-plus.html
- Official project page at Fraunhofer IGB (English): https://www.igb.fraunhofer.de/en/reference-projects/hypowave-plus.html
- Press release (2024): https://www.igb.fraunhofer.de/de/presse-medien/presseinformationen/2024/neuartiger-landwirtschaftlicher-anbau-mit-aufbereitetem-wasser-erstes-reallabor-in-betrieb.html
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