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Bioresour Technol. 2016 Oct;218:1151-6. doi: 10.1016/j.biortech.2016.07.088. Epub 2016 Jul 21.

Struvite crystallization under a marine/brackish aquaculture condition.

Author information

1
Section Sanitary Engineering, Department of Water Management, Delft University of Technology, Stevinweg 1, 2628CN Delft, The Netherlands. Electronic address: x.zhang@tudelft.nl.
2
Section Sanitary Engineering, Department of Water Management, Delft University of Technology, Stevinweg 1, 2628CN Delft, The Netherlands.

Abstract

The results in this study show that struvite was formed in the digester at pH 7.7 due to the magnesium naturally present and the released ammonia and phosphate, resulting in low phosphate concentration in the digester. Apparently the digester already provided proper conditions for struvite formation. Under the brackish condition, the estimated thermodynamic solubility product and enthalpy change of struvite formation were 10(-13.06) and 25.7kJmol(-1), respectively. The average crystal size under marine/brackish condition decreased with pH, but increased with temperature. X-ray diffraction measurements indicate struvite (NH4MgPO4·6H2O) and dittmarite (NH4MgPO4·H2O) were predominant phosphorus species produced in filtrates of the digester. However, struvite and newberyite (HMgPO4·3H2O) were the predominant species precipitated from synthetic brackish waters after dosing MgCl2. It is pronounced that (waste)water characteristics played also an important role on the nature of phosphate precipitates. Under high NH4(+) condition, phosphorus precipitates containing ammonia were dominant, compared to other amorphous phosphates.

KEYWORDS:

Marine/brackish aquaculture condition; Particle size distribution; Standard enthalpy; Struvite crystallization; Thermodynamic solubility product

PMID:
27469096
DOI:
10.1016/j.biortech.2016.07.088
[Indexed for MEDLINE]
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