(677g) Process Simulation Study on the Lifecycle and Techno-Economic Analyses of Electrochemical Phosphate Recovery from Municipal Wastewater Using Sacrificial Magnesium Anode.

Phosphorus (P) is essential for both plant and animal growth. It is a significant element in the global food supply chain and a key component in agricultural fertilizers worldwide. However, it is primarily obtained from finite phosphate rock reserves [1], which are predicted to be consumed during the next century [2]. The concern of unsustainable P reserves, their uneven global distribution, and the increasing demand for P fertilizers due to global population growth create the need for innovative P management approaches [3]. A potentially innovative solution that has emerged is recycling P contained in wastewater streams as struvite fertilizer [4]. This approach does not only conserve P resources but also prevents eutrophication of surface water bodies which impacts biodiversity and water quality [5].

Struvite precipitation is mainly achieved through chemical and electrochemical methods [6]. Chemical struvite precipitation (CSP) typically involves the addition of Mg²⁺ salts and alkalinity (NaOH) to precipitate struvite, while electrochemical struvite precipitation (ESP) adds ions and alkalinity via potentially-driven half-cell reactions at the anode and cathode, respectively, to induce struvite precipitation [7]. The CSP method has received extensive investigations, and industries have successfully commercialized it [7]. However, it has many limitations, such as high chemical cost and sludge [7], [8], which ESP as a new technology, has shown the potential to overcome [9]. Though ESP has proven to be a suitable replacement for CSP, it has not yet been commercialized because several areas of the method have not been fully explored, including the environmental and cost impacts. Consequently, this study will employ process simulation tools to evaluate the electrochemical recovery of P through struvite precipitation from simulated municipal wastewater and conduct techno-economic and life-cycle analyses to forecast the technology’s costs, embodied energy, and emissions and compare with conventional P fertilizer facilities.

The ESP process simulation in this study will be developed using OLI Flowsheet: ESP software (version 11.5) using Mg²⁺ ion from magnesium metal used as a sacrificial anode and stainless steel as the cathode. Prior to using the output of the proposed simulation to study the environmental and cost impacts of the ESP technology, the accuracy of the model’s predictions on P recovery with solution pH, and electrolytic energy consumption with P recovery will be validated through statistical testing using data generated from experimental trials using simulated wastewater solutions.

The lifecycle analysis in this study will follow best practices and will focus on estimating the embodied energy (MJ/ton_P) and carbon emissions (ton_CO2/ton_P) associated with all process consumables (electrical power and chemicals) of the electrochemical P recovery system. Concurrently, the economic sustainability of the ESP process will be evaluated through capital expenses, operating expenses, and profitability analyses.

References

[1] S. Daneshgar, A. Callegari, A. Capodaglio, and D. Vaccari, “The Potential Phosphorus Crisis: Resource Conservation and Possible Escape Technologies: A Review,” Resources, vol. 7, no. 2, p. 37, Jun. 2018, doi: 10.3390/resources7020037.

[2] J. Hallas, C. Mackowiak, A. Wilkie, and W. Harris, “Struvite Phosphorus Recovery from Aerobically Digested Municipal Wastewater,” Sustainability, vol. 11, no. 2, p. 376, Jan. 2019, doi: 10.3390/su11020376.

[3] D. Cordell, J.-O. Drangert, and S. White, “The story of phosphorus: Global food security and food for thought,” Glob. Environ. Change, vol. 19, no. 2, pp. 292–305, May 2009, doi: 10.1016/j.gloenvcha.2008.10.009.

[4] S. R. Golroudbary, M. El Wali, and A. Kraslawski, “Environmental sustainability of phosphorus recycling from wastewater, manure and solid wastes,” Sci. Total Environ., vol. 672, pp. 515–524, Jul. 2019, doi: 10.1016/j.scitotenv.2019.03.439.

[5] S. A. Parsons and J. A. Smith, “Phosphorus Removal and Recovery from Municipal Wastewaters,” Elements, vol. 4, no. 2, pp. 109–112, Apr. 2008, doi: 10.2113/GSELEMENTS.4.2.109.

[6] C. A. Cid, J. T. Jasper, and M. R. Hoffmann, “Phosphate Recovery from Human Waste via the Formation of Hydroxyapatite during Electrochemical Wastewater Treatment,” ACS Sustain. Chem. Eng., vol. 6, no. 3, pp. 3135–3142, Mar. 2018, doi: 10.1021/acssuschemeng.7b03155.

[7] S. Kataki, H. West, M. Clarke, and D. C. Baruah, “Phosphorus recovery as struvite from farm, municipal and industrial waste: Feedstock suitability, methods and pre-treatments,” Waste Manag., vol. 49, pp. 437–454, Mar. 2016, doi: 10.1016/j.wasman.2016.01.003.

[8] Y. Jaffer, T. A. Clark, P. Pearce, and S. A. Parsons, “Potential phosphorus recovery by struvite formation,” Water Res., vol. 36, no. 7, pp. 1834–1842, Apr. 2002, doi: 10.1016/S0043-1354(01)00391-8.

[9] D. Wang et al., “Advanced municipal wastewater treatment and simultaneous energy/resource recovery via photo(electro)catalysis,” Chin. Chem. Lett., vol. 34, no. 5, p. 107861, May 2023, doi: 10.1016/j.cclet.2022.107861.