Struvite precipitation for nutrient recovery from wastewater and sewage sludge has been attracting interest, due to the remarkable fertiliser quality of the product. A method to recover struvite from digested sludge was developed at Stuttgart University, involving first an acidic dissolution of nutrients from digested sludge followed by a precipitation step. The application was first tested in a pilot scale plant and recently upscaled to a semi-industrial size by constructing a recovery plant at a municipal wastewater treatment plant. The study reports on the technical features and the operation of the large-scale plant with a short overview on the pathway leading to the construction, as well as quality of the product.

The proposed innovative technology combines nanocomposite magnetic particles with a tailored adsorbent material for the selective removal of dissolved phosphorus from pretreated wastewater and concentrating it in a purer liquid matrix as a source for further phosphorus recovery. The adsorbent deposited on the carrier magnetic particles was carefully preselected among many other options, showing high adsorption capacity, good selectivity, stability and recovery potential. The engineered composite particles can be magnetically extracted from water, regenerated in an alkaline solution, where phosphorus desorption takes place, and reused again. Their reusability is demonstrated for 55 adsorption/desorption cycles in municipal wastewater by adjusting the process parameters, without detecting any drop in performance. Important advantage of the developed technology is the dual benefit of phosphorus elimination down to concentrations < 5 μg/L PO₄-P and < 50 μg/L Ptotal, which do not pose any eutrophication risk, and the option for subsequent recovery of the valuable nutrient, thus having the potential to be an attractive alternative to the conventional P-removal methods in wastewater treatment.

Newly developed and innovative RUN technology aims to recover nutrients from urban wastewater (blackwater) and biowaste (kitchen waste). The development of RUN technology has been supported by the life cycle assessment (LCA) in order to identify hotspots and trade-offs. While the performance of the process at a laboratory scale did not show any environmental benefits from P recovery, the LCA results have helped to improve the environmental performance at the following scale-up step. The recovery of P on a technical scale was environmentally beneficial, especially in terms of the global warming potential (GWP). However, there were still some trade-offs, e.g., freshwater and marine eutrophication were slightly higher compared to conventional P fertilizer production. Given that P is considered a critical raw material and that climate change is probably the most pressing environmental issue, RUN technology has the potential to deliver on both domains.