Exploration of mechanisms for calcium phosphate precipitation and accumulation in nitrifying granules by investigating the size effects of granules
Exploration of mechanisms for calcium phosphate precipitation and accumulation in nitrifying granules by investigating the size effects of granules
Calcium phosphate could be accumulated in aerobic granules, which attracts attention recently for phosphorus removal and recovery from wastewater. In this study, partial nitrifying granules with high calcium precipitate content were sorted into different size groups for characterization and evaluation to reveal the dynamic balance of granules at stead state and relevant calcium phosphate precipitation and accumulation mechanism. It was found that light yellow small granules without calcium precipitates but high microbial activity co-existed with deep brown granules with calcium precipitate of around 91% and low microbial activity. Characterization with specific oxygen uptake rates, specific ammonium oxidation rates, calcium and phosphate removal rates from solution, EPS contents, elemental compositions by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for different size groups of granules enabled a proposal of a new hypothesized mechanism for calcium precipitation and accumulation. With this proposed mechanism, it is believed that sufficient granule retention time in reactors was critical for the accumulation of calcium precipitates followed by a slow microbial growth rate of biomass due to mass transfer resistance. The co-precipitation of calcium carbonate and calcium phosphate mainly occurred in granules with a size less than 710 µm while calcium phosphate dominant minerals were accumulated in granules larger than 710 µm. The results and conclusions in this study shed light on the mechanisms of calcium phosphate accumulation in granules, which could be used to better operate and control aerobic granular sludge with calcium phosphates for phosphorus removal and recovery.
Calcium phosphate, EPS, HAP, Mechanisms, Nitrifying granules, Phosphorus removal and recovery, Size effects
Liu, Yong-Qiang
75adc6f8-aa83-484e-9e87-6c8442e344fa
Cinquepalmi, Simone
520b7fae-84b8-48bc-8ee2-e304518bfa1f
1 November 2021
Liu, Yong-Qiang
75adc6f8-aa83-484e-9e87-6c8442e344fa
Cinquepalmi, Simone
520b7fae-84b8-48bc-8ee2-e304518bfa1f
Liu, Yong-Qiang and Cinquepalmi, Simone
(2021)
Exploration of mechanisms for calcium phosphate precipitation and accumulation in nitrifying granules by investigating the size effects of granules.
Water Research, 206, [117753].
(doi:10.1016/j.watres.2021.117753).
Abstract
Calcium phosphate could be accumulated in aerobic granules, which attracts attention recently for phosphorus removal and recovery from wastewater. In this study, partial nitrifying granules with high calcium precipitate content were sorted into different size groups for characterization and evaluation to reveal the dynamic balance of granules at stead state and relevant calcium phosphate precipitation and accumulation mechanism. It was found that light yellow small granules without calcium precipitates but high microbial activity co-existed with deep brown granules with calcium precipitate of around 91% and low microbial activity. Characterization with specific oxygen uptake rates, specific ammonium oxidation rates, calcium and phosphate removal rates from solution, EPS contents, elemental compositions by energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and scanning electron microscopy (SEM) for different size groups of granules enabled a proposal of a new hypothesized mechanism for calcium precipitation and accumulation. With this proposed mechanism, it is believed that sufficient granule retention time in reactors was critical for the accumulation of calcium precipitates followed by a slow microbial growth rate of biomass due to mass transfer resistance. The co-precipitation of calcium carbonate and calcium phosphate mainly occurred in granules with a size less than 710 µm while calcium phosphate dominant minerals were accumulated in granules larger than 710 µm. The results and conclusions in this study shed light on the mechanisms of calcium phosphate accumulation in granules, which could be used to better operate and control aerobic granular sludge with calcium phosphates for phosphorus removal and recovery.
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Accepted/In Press date: 7 October 2021
e-pub ahead of print date: 13 October 2021
Published date: 1 November 2021
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© 2021
Keywords:
Calcium phosphate, EPS, HAP, Mechanisms, Nitrifying granules, Phosphorus removal and recovery, Size effects
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Local EPrints ID: 451760
URI: http://eprints.soton.ac.uk/id/eprint/451760
ISSN: 0043-1354
PURE UUID: 7cc26a5d-52b7-44e1-ae38-6ef26da02e77
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Date deposited: 26 Oct 2021 16:30
Last modified: 17 Mar 2024 03:32
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Simone Cinquepalmi
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