As part of the Phos4You project, the Lippeverband tested the suitability of phosphorus recovery at a pre-industrial scale from sewage sludge ashes produced in the Emscher-Lippe-region. At the Remondis Aqua demonstration plant in Werdohl-Elverlingsen, Germany, phosphoric acid was produced from ashes which were generated by the waterboards Emschergenossenschaft and Lippeverband. This demonstrated the feasibility of phosphorus recovery from ashes with low P-load (3-6%). Further relevant results from this pilot study are:
- More than 85 % of the contained phosphorus was recovered, meeting future legal obligations to reach a P-recovery rate > 80%.
- The produced phosphoric acid fulfills the quality criteria of a technical-grade acid for industrial use.
- The by-products, gypsum (construction material) and iron/aluminum salts (precipitant for waste water treatment plans), have low concentrations of contaminants, enabling their recycling.
- The leached ashes residue experienced a positive change concerning its disposal characteristics. Its landfill class has been improved by one level compared to the untreated ashes, and therefore the restrictions and costs for disposal are lower.
Based on the collected process data, a concept for industrial implementation of the Remondis TetraPhos®-process was established for the central sewage sludge treatment location in Bottrop. A first economic viability study was carried out. The Remondis TetraPhos®-process is economically efficient, but – as for every P-recovery process – dependent on the P-load of the ashes as well as the global market price for phosphoric acid.
Due to the low P-load in the Emscher-Lippe-region ashes, a break-even can not be achieved. In the framework of Phos4You, the partners will work on options to increase the P-load in sewage sludge ashes to enhance the economy of the P-recovery process.
Read more about the Remondis TetraPhos®-process: Information sheet in the section “Phos4You documents”: www.nweurope.eu/phos4you