In a report published on 1 November 2026, researchers at RPTU Kaiserslautern-Landau in Germany reviewed how potassium in wastewater could be recovered as fertilizer, potentially supplementing mined potash. Their scoping review examined 110 publications and found that most evidence remains at laboratory scale, with 61 laboratory studies compared with 11 pilot-scale studies. iGrow News
Key takeaways
- The RPTU review covered 110 publications, including 61 laboratory studies and 11 pilot-scale studies, indicating that potassium-recovery technology is still at an early stage. iGrow News
- Wastewater composition was decisive: source-separated urine held about 900 to 2,440 milligrams of potassium per liter, while municipal wastewater after primary settling contained only about 25 milligrams per liter. iGrow News
- Individual studies reported potassium recovery of 15% to 98% for potassium-struvite precipitation and 13% to 95% for electrodialysis, but the authors said differing test conditions prevent direct comparison. iGrow News
- The researchers called for longer pilot tests using real, variable wastewater, extended equipment trials, contaminant screening and life-cycle assessment before full-scale deployment. iGrow News
What happened
Cora Eichholz and Heidrun Steinmetz of RPTU Kaiserslautern-Landau’s Department of Resource-Efficient Wastewater Treatment published their review in the journal Environmental Science and Ecotechnology; it was accepted on 8 October 2026 and publicized on 26 October. iGrow News
The team used the Joanna Briggs Institute framework for scoping reviews, searched the Scopus database and expanded the evidence through citation networks. The 110 publications were grouped by wastewater source, treatment process, technology maturity and fertilizer output. Of the 94 publications examining specific technologies, 40 addressed potassium-struvite precipitation, 17 electrodialysis and 15 ion exchange; around 34% relied on synthetic solutions. iGrow News
The results support different products for different streams. Source-separated urine contained about 900 to 2,440 milligrams of potassium per liter, and liquid digestate about 1,494 to 2,440 milligrams per liter, making those streams more suitable for solid compound fertilizers such as potassium struvite. Municipal wastewater after primary settling contained only about 25 milligrams per liter, which points toward liquid or single-nutrient products if the potassium is first concentrated and separated. iGrow News
Scale-up remains constrained by ammonium and sodium competition, membrane fouling, mineral scaling, energy use and uncertain product purity. The final fertilizer must also be safe, usable and consistent enough for agricultural markets. iGrow News
The review was funded by Germany’s Federal Ministry of Education, Research and Space through the SUSKULT project, with support from RPTU’s Open Access Publication Fund. iGrow News
Specification read
The project scale was not reported: the source gives no plant design flow, population-equivalent loading, duty cycle, treatment capacity or target fertilizer tonnage. The reported “110 publications” is an evidence-base count rather than a wastewater-flow figure, so it cannot be converted into cubic metres per day. iGrow News
For conventional municipal wastewater, the relevant treatment train is screening, primary settling, biological treatment such as A2/O, MBR, MBBR, SBR or UASB, and tertiary treatment or disinfection; DAF or ZLD may be relevant where solids or dissolved salts require additional handling. This research bears directly on the tertiary stage, where potassium concentration and separation could be integrated, although the review does not specify a plant design. iGrow News
If your plant enquiry involves a municipal wastewater flow in m³/day, routine BOD/COD loading, tightening discharge compliance and a possible fertilizer-recovery requirement, this means nutrient recovery should be scoped as a product-quality and side-stream question, not merely as another treatment unit. The operating team would need to establish the potassium-bearing stream, concentrate and separate it, manage competing ions, fouling and scaling, and verify contaminant and product compliance. Buyers can compare membrane-based process alternatives through our chemical treatment applications and MBR membrane systems reference, while the research context is relevant to broader industrial wastewater treatment considerations.
FAQ
Can potassium-recovery equipment be added to an existing municipal wastewater plant?
Potentially at the tertiary stage, but the review did not provide a plant-specific design or retrofit cost. Municipal wastewater after primary settling contained only about 25 milligrams of potassium per liter, so concentration and separation would be needed before the stream could support a liquid or single-nutrient fertilizer product. Source-separated urine and liquid digestate were more concentrated, but their suitability would still depend on composition, fouling, scaling, contaminants and product-quality requirements. iGrow News
What is the expected lead time for a full-scale potassium-recovery project?
The source does not report a procurement lead time or installation schedule. It reports that 11 of the 110 reviewed publications were pilot-scale studies and calls for longer pilot tests on real wastewater, extended equipment trials and life-cycle assessment. A buyer should therefore treat those studies and trials as pre-commercial validation steps before setting a delivery date or committing to a full-scale supplier. iGrow News
Which technology should a plant supplier be able to demonstrate?
The review covers potassium-struvite precipitation, electrodialysis and ion exchange, but its reported recovery figures came from different test conditions and cannot be compared directly. A supplier should demonstrate performance with the plant’s actual wastewater chemistry, including competition from ammonium and sodium, membrane fouling or mineral scaling, energy demand, output purity and consistency. The buyer should also request contaminant screening and evidence of compliance with the European Union Fertilising Products Regulation. iGrow News
How should cost and supplier selection be evaluated?
The source does not provide capital cost, operating cost or a supplier-selection scorecard. The reported technology maturity, reliance on synthetic solutions and need for pilot validation are the available screening criteria, together with energy use, product purity, contaminant control and regulatory compliance. Comparisons should use the same wastewater stream and test conditions rather than recovery percentages drawn from unrelated studies. iGrow News
