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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #229161
Title: Macroscopic and microscopic variation in recovered magnesium phosphate materials: Implications for phosphorus removal processes and product re-use

Author
item MASSEY, MICHAEL - STANFORD UNIVERSITY
item Ippolito, James
item DAVIS, JESSICA - COLORADO STATE UNIVERSITY
item SHEFFIELD, RON - LOUISIANA STATE UNIV.

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2009
Publication Date: 9/29/2009
Citation: Massey, M.S., Ippolito, J.A., Davis, J.G., Sheffield, R.E. 2009. Macroscopic and Microscopic Variation in Recovered Magnesium Phosphate Materials: Implications for Phosphorus Removal Processes and Product Re-use. Bioresource Technology. 101:877-885.

Interpretive Summary: The objective of this study was to examine and characterize crystalline magnesium ammonium phosphate hexahydrate (struvite) recovered from dairy wastewater, crystalline magnesium ammonium phosphate hydrate (dittmarite) recovered from a food processing facility, and a heterogeneous product also recovered from dairy wastewater using “wet” chemical techniques, powder x-ray diffraction (XRD), and scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy (SEM-EDS). Struvite crystals had regular and consistent shape, size, and structure, and SEM-EDS analysis clearly showed the struvite crystals as a surface precipitate on calcium phosphate seed material. Dittmarite crystals showed no evidence of seed material, and were not regular in size or shape. XRD analysis identified no crystalline magnesium phosphates in the heterogeneous product and indicated the presence of sand particles, while magnesium phosphate precipitates on calcium phosphate seed material were observed in this product under SEM-EDS examination. Macroscopic/microscopic characteristic variations of magnesium phosphates recovered under field conditions could affect their potential for beneficial re-use.

Technical Abstract: Phosphorus (P) recovery and re-use will become increasingly important for water quality protection and sustainable nutrient cycling as environmental regulations become stricter and global P reserves decline. The objective of this study was to examine and characterize several magnesium phosphates recovered from actual wastewater under field conditions. Three types of particles were examined including crystalline magnesium ammonium phosphate hexahydrate (struvite) recovered from dairy wastewater, crystalline magnesium ammonium phosphate hydrate (dittmarite) recovered from a food processing facility, and a heterogeneous product also recovered from dairy wastewater. The particles were analyzed using “wet” chemical techniques, powder x-ray diffraction (XRD), and scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy (SEM-EDS). The struvite crystals had regular and consistent shape, size, and structure, and SEM-EDS analysis clearly showed the struvite crystals as a surface precipitate on calcium phosphate seed material. In contrast, the dittmarite crystals showed no evidence of seed material, and were not regular in size or shape. The XRD analysis identified no crystalline magnesium phosphates in the heterogeneous product and indicated the presence of sand particles. However, magnesium phosphate precipitates on calcium phosphate seed material were observed in this product under SEM-EDS examination. These substantial variations in the macroscopic and microscopic characteristics of magnesium phosphates recovered under field conditions could affect their potential for beneficial re-use and underscore the need to develop recovery processes that result in a uniform, consistent product.