This research investigated an integrated, multi-process approach to produce separate nutrient products that can then be recombined to produce customized fertilizers of any NPK ratio using struvite precipitation, ammonia stripping–acid absorption, and evaporation to recover phosphorus (P), nitrogen (N), and potassium (K), respectively, from hydrolyzed urine. Bench scale experiments were conducted using three hydrolyzed urine solutions: synthetic urine, synthetic urine with six endogenous metabolites, and real urine. For struvite precipitation, MgCl2 6H2O, MgCO3, and MgO were tested and dosed at a molar ratio of 1.1:1 Mg:P. There was a statistically significant difference between total phosphorus (TP) recovery by each magnesium (Mg) source and urine solution; MgCl2 6H2O (99–100% TP recovered) &gt; MgCO3 (55–77%) &gt; MgO (52–66%) and real urine &gt; synthetic urine with six endogenous metabolites &gt; synthetic urine. For ammonia stripping–acid absorption, five conditions with varying pH and temperature were tested. There was no statistically significant difference in total ammonia nitrogen (TAN) recovery due to the Mg source used in struvite precipitation or the urine solution, however, there was a statistically significant difference in TAN recovery by experimental stripping conditions. Increasing both the pH and temperature recovered a higher percent of TAN compared to solely increasing the pH or temperature. In real urine, consumed cost for stripping increased as follows: control condition of pH 9.2, 22°C &lt; elevated temperature condition of pH 9.2, 70°C &lt; elevated pH condition of pH 10.5, 22°C. For evaporation, there was only a statistically significant difference between K recovery by ammonia stripping–acid absorption conditions where pH 9.2, 22°C &gt; pH 10, 40°C &gt; pH 9.6, 55°C &gt; pH 10.5, 22°C. Reduced purity of the final K product was observed as pH was increased due to sodium from NaOH. Results show nutrient recovery in real urine ( 99 % N, 99% P, and 80% K recovered as fertilizer products) was consistently greater than or equivalent to synthetic urine.

Integrated, multi-process approach to total and customizable nutrient recovery from hydrolyzed urine

256th National Meeting (2018)

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