Speaker
Description
The essential nutrient phosphorus is mined in only a few regions of the world and is mainly processed into fertilizers distributed worldwide. Its limited availability, together with increasing geopolitical uncertainties, highlights the need for a more resilient and circular phosphorus supply. Recovering phosphorus from wastewater treatment plants (WWTPs) is a promising approach to closing the phosphorus loop (Raniro et al. 2025).
In municipal wastewater treatments (WWTP), phosphorus is removed by biological uptake and, in some countries like Germany, by chemical precipitation, mainly using iron salts (Barjenbruch et al. 2024). As a result, most phosphorus is transferred to sewage sludge, which can be used as resource for phosphorus recovery (Raniro et al. 2025). One recovery approach is the Stuttgart Process, in which phosphorus is released by acidification and subsequently precipitated as struvite using ammonia from the sewage sludge and an external magnesium source (Meyer et al. 2019). At the WWTP Offenburg, phosphorus leaching efficiencies ranged from 40–70% at pH 3.5–4.5 (n = 18) (Meyer et al. 2019). These variations could not be explained by the measured sludge composition or the applied pH alone (Mohn et al. 2017). Further laboratory studies showed that ion concentrations and target pH influence phosphorus leaching but could not fully explain the observed variability (Monea et al. 2020; Keller et al. 2022).
This presentation introduces the motivation for phosphorus recovery from wastewater and presents the current challenges in evaluating a large dataset to better understand the factors affecting the leaching efficiency in the first step of the Stuttgart Process.
This project is funded by the German Research Foundation (Deutsche Forschungsgemeinschaft – DFG) as part of the Research Training Group 2908 "Valuable Wastewater (WERA) - Recovery of Critical Raw Materials by the Example of Phosphorus".
