title: Apatite accumulation enhances the mechanical property of anammox granules.
abstract: The strength of granular sludge is essential for the mechanical stability of the granules. Inorganic precipitants form a major factor influencing the strength of the granules. To check the possibility of apatite accumulation in anammox granules, and study its contribution to the mechanical strength of granules, anammox granular sludge was collected from Dokhaven municipal wastewater treatment plant, the Netherlands. Mineral precipitation inside the granules was visualized by micro-computed tomography, and apatite was identified by electron probe microanalysis and X-ray powder diffraction. The mechanical strength of anammox granules was measured by a low load compression tester. The contribution of apatite to the mechanical strength was evaluated by the generalized Maxwell model. Ca-PO4 minerals are reported to accumulate in anammox granules. A transformation of Ca-PO4 happens, and apatite is the final stable form. The accumulation of apatite increases the mechanical strength of anammox granules. A fast method to monitor and evaluate the accumulation of minerals in anammox granules was proposed.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628BC Delft, The Netherlands. Yuemei.Lin@tudelft.nl
authors.forename: Y M
authors.initials: YM
authors.lastname: Lin
authors.forename: T
authors.initials: T
authors.lastname: Lotti
authors.forename: P K
authors.initials: PK
authors.lastname: Sharma
authors.forename: M C M
authors.initials: MC
authors.lastname: van Loosdrecht
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000693:Anaerobiosis; D001031:Apatites / Q000032:analysis*; D019149:Bioreactors / Q000382:microbiology; D011232:Chemical Precipitation; D004577:Electron Probe Microanalysis; D005612:Freeze Drying; D055595:Mechanical Phenomena; D009426:Netherlands; D010084:Oxidation-Reduction; D010316:Particle Size; D010758:Phosphorus / Q000032:analysis; D011208:Powders; D012722:Sewage / Q000737:chemistry*; D013997:Time Factors; D014865:Waste Disposal, Fluid; D014961:X-Ray Diffraction; D055114:X-Ray Microtomography
chemical_list: D001031:Apatites; D011208:Powders; D012722:Sewage; D010758:Phosphorus; D000641:Ammonia
keywords: Anammox; Apatite; Granular sludge; Mechanical strength; Phosphate