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ABSTRACT
Since phosphorus (P) is a nonrenewable element essential for life, it is extremely important to understand its potential supply sources. This paper describes the behavior of P during the ozonation of waste activated sludge (WAS) as it is an important pool of P. Also, we investigated whether ozonation of WAS could be an effective method for both P recovery in solution and its bio- and plant-availability in solid residues based on the analysis by the Standards, Measurements, and Testing Program. The results showed that P was enriched in WAS at concentrations above 23 mg/g. Phosphorus transferred from the solid phase to the liquid phase, and the total P content in the liquid phase increased from 1.67 to 40.68 mg/L as the ozone dosage increased from 0 to 0.20 g O3/g MLSS. PO43–P was the main form of P in the liquid phase after ozonation, which is beneficial for P recovery. The P fraction analysis revealed that the released P mainly came from apatite P (AP) during ozonation. Additionally, P was more available in solid residues as the proportion of bio-available P (non-apatite inorganic P (NAIP) + organic P (OP)) improved from 73.6% in the raw WAS to 91.7% at an ozone dosage of 0.20 O3/g MLSS. In addition, the solid residues were suitable for plant availability at a moderate Fe/P ratio (0.91) after ozonation. Thus, ozonation is recommended as the preferable solution to achieve an advanced P supply in both the liquid phase and solid residues.
Ethics approval
Compliance with Ethical Standards.
Data availability statement
The data that support the findings of this study are available from the corresponding author, Zaixing Li, upon reasonable request.
Consent to publish statement
The manuscript is approved by all authors for publication.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Author contributions
Y Liu: conceptualization, investigation, writing - original draft, funding acquisition. W Gao: formal analysis, investigation, writing - original draft. S Yin: formal analysis, investigation, editing. X Lou: investigation, experimental materials provided. G Li: investigation, experimental materials provided. H Liu: investigation, experimental materials provided. Z Li: supervision, writing - review and editing, funding acquisition.