Microbial removal of nutrients from anaerobic digestate: assessing product-coupled and non-product-coupled approaches

Eric Agyeman-Duah; Christopher C Okonkwo; Victor C Ujor

doi:10.3389/fmicb.2023.1299402

Microbial removal of nutrients from anaerobic digestate: assessing product-coupled and non-product-coupled approaches

Front Microbiol. 2023 Dec 11:14:1299402. doi: 10.3389/fmicb.2023.1299402. eCollection 2023.

Authors

Eric Agyeman-Duah¹, Christopher C Okonkwo², Victor C Ujor¹

Affiliations

¹ Fermentation Science and Metabolic Engineering Group, Department of Food Science, University of Wisconsin-Madison, Madison, WI, United States.
² Biotechnology Program, Department of Chemistry and Chemical Biology, The Roux Institute, Northeastern University, Portland, ME, United States.

Abstract

Although anaerobic digestate contains >90% water, the high nutrient content of digestate makes it economically and technically intractable to treatment by existing wastewater treatment technologies. This study separately assessed the feasibility of nutrient removal from digestate by Rhizopus delemar DSM 905 and a culture of phosphate-accumulating organisms (PAOs). With Rhizopus delemar DSM 905, we investigated concomitant nutrient removal from digestate-supplemented medium and fumaric acid production, as a potentially economical strategy for digestate treatment. Following the cultivation of R. delemar DSM 905 in a fermentation medium containing 25% (v/v) digestate, the concentrations of Al, Cr, Cu, Fe, K, Mg, Mn, Pb, and Zn reduced 40, 12, 74, 96, 12, 26, 23%, ~18, and 28%, respectively. Similarly, the concentrations of total phosphorus, total nitrogen, phosphate (PO₄-P), ammonium (NH₄-N), nitrate (NO₃-N), and sulfur decreased 93, 88, 97, 98, 69, and 13%, respectively. Concomitantly, cultures supplemented with 25 and 15% (v/v) digestate produced comparable titers of fumarate (~11 and ~ 17 g/L, respectively) to the digestate un-supplemented control cultures. With PAOs, we assessed the removal of total phosphorus, total nitrogen, PO₄-P, and NH₄-N, of which the concentrations reduced 86, 90%, ~99, and 100%, respectively in 60% (v/v) digestate. This study provides additional bases for microbial removal of excess nutrients from anaerobic digestate, with the potential to engender future water recovery from this waste stream that is currently largely recalcitrant to treatment.

Keywords: anaerobic digestate; fumaric acid; microbial nutrient removal; phosphate removal; phosphate-accumulating organisms.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was financially supported by the Office of the Vice Chancellor for Research and Graduate Education at the University of Wisconsin-Madison, with funding from the Wisconsin Alumni Research Foundation.