1–5 Urine is a unique waste stream because it contains several plant nutrients-nitrogen (N), phosphorus (P), potassium (K), sulfur (S), chloride (Cl −), and magnesium (Mg 2+). Introduction The separation and treatment of urine has gained considerable attention in the past two decades as a viable process for producing fertilizer. Separation and treatment of urine can recover nitrogen, phosphorus, and potassium as separate products of value, thereby reducing the negative impacts of nutrients on the environment.ġ. Unlike traditional fertilizer production that requires finite resources, urine is widely available. Water impact Urine is a unique waste stream because it contains nutrients that are valuable in agriculture yet problematic in excess in aquatic environments. Results from this study show that an integrated, multi-process approach to urine treatment can achieve approximately 99% N, 91% P, and 80% K recovery as fertilizer products. As the pH was increased, the purity of the final K product, potash, decreased due to sodium from NaOH. For evaporation, there was a statistically significant difference between the urine solution and conditions for N recovery ( i.e., temperature and/or pH) on K recovery and product purity. This suggests that using synthetic urine as a proxy for real urine is not suitable for N recovery. Furthermore, the amount of TAN recovered in real urine and synthetic urine with metabolites was consistently greater than or approximately equal to synthetic urine. There was no statistically significant difference between the Mg source and TAN recovery in real urine and synthetic urine with metabolites but there was in synthetic urine. In real urine, consumed cost for stripping increased as follows: control condition of pH 9.2, 22 ☌ < elevated pH condition of pH 10.5, 22 ☌ < elevated temperature condition of pH 9.2, 70 ☌. For ammonia stripping–acid absorption, there was a statistically significant difference between TAN recovery and experimental stripping conditions where increasing both the pH and temperature recovered a higher percent of TAN compared to solely increasing the pH or temperature of the solution. There was a statistically significant difference between total phosphate (TP) recovered by each magnesium (Mg) source and urine solution MgCl 2♶H 2O (91–94% TP recovered) > MgCO 3 (55–77%) > MgO (52–66%) and real urine > synthetic urine with six endogenous metabolites > synthetic urine. For struvite precipitation, MgCl 2♶H 2O, MgCO 3, and MgO were tested and dosed at a molar ratio of 1.1 : 1 Mg : P. Bench-scale experiments were conducted using three stored urine solutions: synthetic urine, synthetic urine with six endogenous metabolites, and real urine. The process produces separate nutrient products that can then be recombined to produce customized fertilizers of any NPK ratio. This study investigated an integrated, multi-process approach of using struvite precipitation, ammonia stripping–acid absorption, and evaporation to recover phosphorus (P), nitrogen (N), and potassium (K), respectively, from stored urine.
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