Recovering Nitrogen as a Solid without Chemical Dosing: Bio-Electroconcentration for Recovery of Nutrients from Urine
2017
Ledezma, Pablo | Jermakka, Johannes | Keller, J. (Jurg) | Freguia, Stefano
This letter presents the proof of concept of a novel bio-electroconcentration system (BEC), a hybrid microbial electrolysis/electrodialysis cell specifically designed to recover nitrogen (as ammonia NH₄-N), phosphorus (as phosphate PO₄-P), and potassium (as K⁺) from urine. Using a synthetic urine medium, the BECs could reach high current densities of up to 37.6 A m–² at Ewₑ values of 0.0 versus the standard hydrogen electrode (SHE) and 50 A m–² at 0.2 V versus SHE, which in turn drove the removal and recovery of N, P, and K at rates of 7.18 kg of NH₄-N m–³ day–¹, 0.52 kg of PO₄-P m–³ day–¹, and 1.62 kg of K⁺ m–³ day–¹ into a concentrate stream (containing 1.87 M NH₄-N, 0.29 M PO₄-P, and 0.18 M K⁺). Finally, this communication demonstrates the recovery of a nitrogen-rich solid from the synthetic urine (in the form of pure NH₄HCO₃ crystals with 17% N content) without any chemical additions via the flash-cooling of the produced nutrient-rich concentrate to 4 °C. These two new products may help facilitate the reuse of urine nutrients in the fertilizer or protein production industries of the future.
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