Considering the limited literature and the difficulty of quantifying 1-μm micro-nanoplastics (1-μm MNP) in complex aqueous matrices such as wastewater and sludge, the removal rate of these very small particles in wastewater treatment plants (WWTP) represents a major challenge. In this study, coagulation-flocculation-sedimentation (CFS) with aluminum salts was investigated to evaluate the removal of 1-μm MNPs spiked in tap water, raw wastewater, pre-settled wastewater, and activated sludge. Quantification of 1-μm MNP was performed using the high-throughput flow cytometry (FCM) analysis which takes only a few minutes and produces results with high accuracy and reproducibly. The results indicated that the 1-μm MNPs were highly stable in pure water and unable to settle rapidly. In raw wastewater, sedimentation without coagulants removed less than 4% of 1-μm MNP. Conversely, CFS treatment showed a significant improvement in the removal of 1-μm MNP from wastewater. At dosages of 0.3-3 mg Al3+/L, the removal of MNPs in wastewater reached 30% and no flocs were observed, while floc formation was visible with increased dosages of 3-12 mg Al3+/L, obtaining MNP removal greater than 90%. CFS in activated sludge with a solids content of 5800 mg MLSS/L registered the highest removal efficiency (95-99%) even for dosages of 0.3-60 mg Al3+/L and pH dropping to 5. However, activated sludge showed extremely high removal efficiency of MNPs (97.3 ± 0.9%) even without coagulants. The large, dense flocs that constitute activated sludge appear particularly efficient in capturing 1-μm MNPs during the sedimentation process even in the absence of coagulants.

Flow cytometry as a tool for the rapid enumeration of 1-μm microplastics spiked in wastewater and activated sludge after coagulation-flocculation-sedimentation / Foladori, Paola; Lucchini, Giulia; Torboli, Alessia; Bruni, Laura. - In: CHEMOSPHERE. - ISSN 0045-6535. - STAMPA. - 359:(2024), pp. 14232801-14232810. [10.1016/j.chemosphere.2024.142328]

Flow cytometry as a tool for the rapid enumeration of 1-μm microplastics spiked in wastewater and activated sludge after coagulation-flocculation-sedimentation

Foladori, Paola
Primo
;
Torboli, Alessia
Penultimo
;
2024-01-01

Abstract

Considering the limited literature and the difficulty of quantifying 1-μm micro-nanoplastics (1-μm MNP) in complex aqueous matrices such as wastewater and sludge, the removal rate of these very small particles in wastewater treatment plants (WWTP) represents a major challenge. In this study, coagulation-flocculation-sedimentation (CFS) with aluminum salts was investigated to evaluate the removal of 1-μm MNPs spiked in tap water, raw wastewater, pre-settled wastewater, and activated sludge. Quantification of 1-μm MNP was performed using the high-throughput flow cytometry (FCM) analysis which takes only a few minutes and produces results with high accuracy and reproducibly. The results indicated that the 1-μm MNPs were highly stable in pure water and unable to settle rapidly. In raw wastewater, sedimentation without coagulants removed less than 4% of 1-μm MNP. Conversely, CFS treatment showed a significant improvement in the removal of 1-μm MNP from wastewater. At dosages of 0.3-3 mg Al3+/L, the removal of MNPs in wastewater reached 30% and no flocs were observed, while floc formation was visible with increased dosages of 3-12 mg Al3+/L, obtaining MNP removal greater than 90%. CFS in activated sludge with a solids content of 5800 mg MLSS/L registered the highest removal efficiency (95-99%) even for dosages of 0.3-60 mg Al3+/L and pH dropping to 5. However, activated sludge showed extremely high removal efficiency of MNPs (97.3 ± 0.9%) even without coagulants. The large, dense flocs that constitute activated sludge appear particularly efficient in capturing 1-μm MNPs during the sedimentation process even in the absence of coagulants.
2024
Foladori, Paola; Lucchini, Giulia; Torboli, Alessia; Bruni, Laura
Flow cytometry as a tool for the rapid enumeration of 1-μm microplastics spiked in wastewater and activated sludge after coagulation-flocculation-sedimentation / Foladori, Paola; Lucchini, Giulia; Torboli, Alessia; Bruni, Laura. - In: CHEMOSPHERE. - ISSN 0045-6535. - STAMPA. - 359:(2024), pp. 14232801-14232810. [10.1016/j.chemosphere.2024.142328]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/410696
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