Struvite Production from Dairy Processing Waste

Shane McIntosh (), Louise Hunt, Emma Thompson Brewster, Andrew Rose, Aaron Thornton and Dirk Erler
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Shane McIntosh: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Louise Hunt: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Emma Thompson Brewster: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Andrew Rose: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Aaron Thornton: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia
Dirk Erler: Faculty of Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia

Sustainability, 2022, vol. 14, issue 23, 1-15

Abstract: Food security depends on sustainable phosphorus (P) fertilisers, which at present are mostly supplied from a finite rock phosphate source. Phosphate (PO 4 3− ) and ammonium (NH 4 + ) in dairy processing wastewater can be recovered as struvite (Mg + NH 4 + + PO 4 3− 6H 2 0), a nutrient rich mineral for fertiliser application. The objectives of this study were to (1) quantify the effects of, pH, temperature and Mg: PO 4 3− dosing rates on nutrient (PO 4 3− and NH 4 + ) removal and struvite precipitation from post anaerobic digested dairy processing wastewater, and (2) co-blend different dairy processing wastewaters to improve the reactant stoichiometry of NH 4 + and PO 4 3− for optimal struvite recovery and NH 4 + removal. Phosphate removal (>90%) and struvite production (>60%) was achieved across a range of synthesis conditions, and was significantly impacted by pH as determined by response surface modelling. A combination of disproportionate molar ratios of PO 4 3− and NH 4 + , presence of calcium and the apparent mineralisation of organic N, resulted in co-precipitation of hydroxyapatite and elevated levels of residual aqueous NH 4 + . In the second phase of this study, struvite was successfully precipitated and NH 4 + removal was improved (~17%) however, higher concentrations of calcium in the wastewater blends resulted in greater hydroxyapatite co-precipitation (up to 30%). While struvite was the desired product in this study the formation of multiple heterogenous P-rich products (struvite and hydroxyapatite) has the potential to improve P recovery from dairy processing wastewaters and produce a fertiliser blend with amenity and value in agricultural systems.

Keywords: dairy processing waste; food security; phosphorus recovery; struvite; sustainable agriculture (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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