Struvite Precipitation from Centrate—Identifying the Best Balance Between Effectiveness and Resource Efficiency

Andreas Kolb (), Tim Gebhardt and Thomas Dockhorn
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Andreas Kolb: Institute of Sanitary and Environmental Engineering, Technische Universität Braunschweig, Pockelsstraße 2a, 38106 Braunschweig, Germany
Tim Gebhardt: Institute of Sanitary and Environmental Engineering, Technische Universität Braunschweig, Pockelsstraße 2a, 38106 Braunschweig, Germany
Thomas Dockhorn: Institute of Sanitary and Environmental Engineering, Technische Universität Braunschweig, Pockelsstraße 2a, 38106 Braunschweig, Germany

Resources, 2025, vol. 14, issue 4, 1-18

Abstract: In the context of struvite precipitation, the most significant gap pertains to the transfer of knowledge from scientific research to practical applications. The primary objective of this study is twofold: firstly, to identify the most critical process parameters influencing struvite precipitation and, secondly, to translate these parameters into a pragmatic tool for real-world applications. This study investigates the precipitation of struvite from digestion centrate to obtain information on the appropriate precipitation conditions for different initial chemical compositions. We carried out 24 lab-scale experiments to investigate the effect of varying pH value (7.0–8.5), temperature (5 °C and 33 °C) and initial phosphate concentrations (353; 165; 68 mg/L) on struvite precipitation. Varying the pH had the strongest influence on precipitation efficiencies. Adjusting pH from 7 to 8.5 increased PO 4 -P removal from 1.4% to 98.8%, whereas temperature had little impact on PO 4 -P removal. Furthermore, we found that a saturation index of at least 1.7 is imperative to precipitate at least 90% of the available PO 4 -P. Based on the results, we developed a nomogram showing the resulting saturation index and the associated PO 4 -P removal efficiency for variable initial PO 4 -P and pH levels. The tool developed in this study enables users to directly identify the so-called ‘sweet spot’, which is the optimal balance between process effectiveness and resource efficiency, for each centrate.

Keywords: magnesium–ammonium–phosphate; phosphorous recovery; anaerobic digestion centrate; nutrient recycling; saturation index (search for similar items in EconPapers)
JEL-codes: Q1 Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2025
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