Pulsed Corona Discharge in Valorisation of Urine as a Sustainable Source of Nutrients: Targeted Oxidation of Pharmaceutical Residues and Inhibition of Urea Enzymatic Hydrolysis

Human urine is a sustainable source of nutrients with significant fertilizer potential. The presence of pharmaceutical residues, however, obstructs its use in agriculture. Also, the loss of ammonia formed in enzyme-catalyzed hydrolysis of urea in stored urine compromises the approach. This study presents gas-phase pulsed corona discharge (PCD) used in the oxidation of pharmaceuticals and enzymes, improving the applicability of urine as a fertilizer. The prioritized beta-blocker propranolol (PR) and antibiotic tetracycline were chosen as target micropollutants for the experimental study, demonstrating enhanced oxidation relative to matrix constituents. Tetracycline showed its more recalcitrant character in urine than PR for its more pronounced matrix-mediated scavenging or complexation. The PCD oxidation significantly lowered the urease enzyme activity, thus preventing nitrogen loss through ammonia volatilization. According to the phytotoxicity assessment using the Pisum sativum garden peas test, urine PCD-treated with the energy dose sufficient to substantially degrade pharmaceuticals is not phytotoxic when applied at recommended agronomic doses. The findings reveal the use of PCD as an energy-efficient technology for producing safe and stable urine-derived fertilizer.