Struvite for Recovery of N&P and Ozone Oxidation of Residual Pharmaceuticals in Human Urine

Abstract

An experimental study was conducted for struvite formation to recover N&P and ozone (O3) oxidation to remove residual pharmaceuticals in human urine. Sea water reverse osmosis (SWRO) concentrate was used as a magnesium source in the struvite production using hydrolyzed urine. The condition of struvite formation was set at pH 10 and volumetric ratio of the SWRO concentrate to urine 0.1 to adjust Mg/P molar ratio of 1.4. The residual pharmaceuticals were analyzed by LC/MS with solid-phase extraction (SPE) as a pre-treatment of samples. O3 oxidation was carried out at pH 11, O3 injection range 1 to 5 mg/L and contact time 15 minutes. The hydrolyzed urine contained N&P 4,117 mg/L and 638 mg/L mostly in the form of NH3-N (3,784 mg/L) and PO4-P (601 mg/L), of which 2.3% and 92.7% were recovered, respectively in formation of the struvite (2.65 g/L-urine). Caffeine (3,329 μg/L), diclofenac (666 μg/L) and ibuprofen (408 μg/L) were three major pharmaceuticals detected in the urine sample. The pharmaceutical content of the struvite was 57.21 μg/g for caffeine, 12.87 μg/g for diclofenac and 8.94 μg/g for ibuprofen. 43.9% of caffeine in the urine was removed at 1 mg/L of O3 injection, 33.6% for diclofenac at 4 mg/L and 28.68% for ibuprofen at 3 mg/L. It was considered that the O3 oxidation of the urine could reduce the pharmaceutical content in the struvite and encourage use of the struvite derived from the human urine as an agricultural fertilizer. Key words: Human Urine, Nitrogen and Phosphorus Recovery, Ozone Oxidation, Pharmaceuticals in urine, Seawater Reverse Osmosis Concentrate, Struvite