title: Phosphorus recovery: minimization of amount of pharmaceuticals and improvement of purity in struvite recovered from hydrolysed urine.
abstract: Struvite (MgNH₄PO₄·6H₂O) is normally used as a fertilizer in agriculture, where struvite crystallization from hydrolysed human urine is a simple and reliable method for phosphorus (P) recovery. Human urine, however, contains high amount of pharmaceuticals, which may cause health risk for applications. This research investigates the possibility of decreasing the amount of pharmaceuticals (tetracycline, demeclocycline and oxytetracycline) in struvite crystals recovered from synthetic and human urines by focusing on storage time, and of increasing the quality of struvite production. Urines were stored for different times up to 15 days prior to recovery of phosphorus by two steps, spontaneous precipitation and struvite crystallization. The morphology of spontaneous precipitates and struvite crystals was observed. Spontaneous precipitation removed around 17-24% of phosphate from synthetic and human urines, while pharmaceuticals were removed with a quite high amount at a short storage time (5 days) and this amount decreased with increasing the storage time (10 and 15 days). Urines with>70% remaining phosphates were re-used for struvite crystallization by adding extra magnesium. It was found that maximum P-recovery efficiency could be achieved from struvite crystallization at 5-day storage time, 70% and 68% of remaining P in the separated supernatant from synthetic and human urines, respectively, whereas less than 1% pharmaceuticals remained in the struvite crystals from both samples. This indicates that the procedure in this work is a good method for phosphorus recovery, in which high struvite purity (>99%) is obtained with low amount of pharmaceuticals.
authors.affiliation: a Center of Excellence on Hazardous Substance Management, Department of Environmental Engineering, Faculty of Engineering , King Mongkut's University of Technology Thonburi , 126 Pracha-Uthit Rd., Bangmod, Tungkru , Bangkok 10140 , Thailand.
authors.forename: Patiya
authors.initials: P
authors.lastname: Kemacheevakul
authors.forename: Surawut
authors.initials: S
authors.lastname: Chuangchote
authors.forename: Sosuke
authors.initials: S
authors.lastname: Otani
authors.forename: Tomonari
authors.initials: T
authors.lastname: Matsuda
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Shimizu
mesh_terms: D003460:Crystallization; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D017616:Magnesium Compounds / Q000737:chemistry* / Q000652:urine; D010710:Phosphates / Q000737:chemistry* / Q000652:urine; D010758:Phosphorus / Q000737:chemistry / Q000302:isolation & purification* / Q000652:urine; D013048:Specimen Handling / Q000379:methods; D000069877:Struvite; D013754:Tetracyclines / Q000032:analysis*; D013997:Time Factors
chemical_list: D017616:Magnesium Compounds; D010710:Phosphates; D013754:Tetracyclines; D010758:Phosphorus; D000069877:Struvite
keywords: human urine; pharmaceutical; scanning electron microscope; storage time; struvite