Variation in phosphorus speciation of sewage sludge throughout three wastewater treatment plants: Determined by sequential extraction combined with microscopy, NMR spectroscopy, and powder X-ray diffraction

Qian Wang, Chitra S. Raju, Nina Almind-Jørgensen, Mikkel Laustrup, Kasper Reitzel, Ulla Gro Nielsen*

*Kontaktforfatter for dette arbejde

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Abstrakt

The variation in phosphorus (P) speciation of sewage sludge throughout three wastewater treatment plants (WWTPs) was obtained by combining sequential P extraction with optical and scanning electron microscopy (SEM), chemical analyses, powder X-ray diffraction (PXRD), and 27Al and 31P nuclear magnetic resonance (NMR) spectroscopy. The WWTPs combine chemical P removal (CPR) and enhanced biological P removal (EBPR) and were compared to understand the effect of iron (Fe) dosing with and without codosing of aluminum (Al) and thermal hydrolysis on the P speciation. 31P NMR showed comparable inorganic orthophosphate (ortho-P, 53-60% of total P) and organophosphate (organic-P, 37-45%) in primary sludge, whereas polyphosphate (poly-P, 23-44%) from poly-P accumulating organisms (PAOs) was mainly observed in the secondary sludge. Inorganic ortho-P (90-98%) dominated after anaerobic digestion, which degraded poly-P and most organic-P. The inorganic ortho-P was mainly Fe bound P (Fe-P), especially after anaerobic digestion (71%). Codosing of Fe and Al led to two comparable fractions: Fe-P (38%) and P sorbed on amorphous Al (hydr)oxides (38%). Vivianite was identified in all samples by microscopy and chemical extraction but was PXRD amorphous in 12 out of 17 samples. Thus, vivianite may be more common in sewage sludge than previously known.

OriginalsprogEngelsk
TidsskriftEnvironmental Science and Technology
Vol/bind56
Udgave nummer12
Sider (fra-til)8975-8983
ISSN0013-936X
DOI
StatusUdgivet - 21. jun. 2022

Bibliografisk note

Funding Information:
This work was funded by Vandsektorens Udviklings- og Demonstrationsprogram (VUDP, project 03.2020) and the Poul Due Jensen/Grundfos Foundation (2020-068).

Publisher Copyright:
© 2022 American Chemical Society.

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