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Article

Removal of Toxic Metals from Sewage Sludge by Acid Hydrolysis Coupled with EDTA Washing in a Closed-Loop Process

1
Agronomy Department, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia
2
Faculty of Mechanical Engineering, University of Ljubljana, Askerceva Cesta 6, 1000 Ljubljana, Slovenia
3
Envit Ltd., Trzaska Cesta 330, 1000 Ljubljana, Slovenia
*
Author to whom correspondence should be addressed.
Int. J. Environ. Res. Public Health 2023, 20(3), 2544; https://doi.org/10.3390/ijerph20032544
Submission received: 20 December 2022 / Revised: 26 January 2023 / Accepted: 27 January 2023 / Published: 31 January 2023
(This article belongs to the Special Issue The Wastewater: Treatment and Remediation)

Abstract

Contamination with toxic metals prevents the use of sewage sludge (SS) as a soil fertilizer. Hydrodynamic cavitation, thermal microwaving, microwave-assisted alkaline, and acid hydrolysis coupled with ethylenediaminetetraacetate (EDTA) washing were tested as a method to remove toxic metals from SS. Acid hydrolysis coupled with EDTA washing was most effective and was used in a closed-loop process based on ReSoil technology. EDTA and process solutions were recycled at a pH gradient of 12.5–2, which was imposed by the addition of quicklime (CaO) and H2SO4. An average of 78%-Pb, 76%-Zn, 1%-Cu, and 17%-Cr were removed from SS in five consecutive batches. No wastewater was generated, only solid waste (40%). The EDTA lost in the process (42%) was resupplied in each batch. In a series of batches, the process solutions retained metal removal efficiency and quality. The treatment removed 70% and 23% of P and N, respectively, from SS and increased the leachability of Zn, Cu, Mn, and Fe in the washed SS by 11.7, 6.8, 1.4, and 5.2 times, respectively. Acid hydrolysis coupled with EDTA washing proved to be a technically feasible, closed-loop process but needs further development to reduce reagent, material, and nutrient loss and to reduce toxic emissions from the washed sludge.
Keywords: sewage sludge; toxic metals; EDTA; hydrolysis; microwaves; cavitation; phosphorus sewage sludge; toxic metals; EDTA; hydrolysis; microwaves; cavitation; phosphorus
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MDPI and ACS Style

Morales Arteaga, J.F.; Zupanc, M.; Dular, M.; Lestan, D.; Kaurin, A. Removal of Toxic Metals from Sewage Sludge by Acid Hydrolysis Coupled with EDTA Washing in a Closed-Loop Process. Int. J. Environ. Res. Public Health 2023, 20, 2544. https://doi.org/10.3390/ijerph20032544

AMA Style

Morales Arteaga JF, Zupanc M, Dular M, Lestan D, Kaurin A. Removal of Toxic Metals from Sewage Sludge by Acid Hydrolysis Coupled with EDTA Washing in a Closed-Loop Process. International Journal of Environmental Research and Public Health. 2023; 20(3):2544. https://doi.org/10.3390/ijerph20032544

Chicago/Turabian Style

Morales Arteaga, Juan Francisco, Mojca Zupanc, Matevž Dular, Domen Lestan, and Anela Kaurin. 2023. "Removal of Toxic Metals from Sewage Sludge by Acid Hydrolysis Coupled with EDTA Washing in a Closed-Loop Process" International Journal of Environmental Research and Public Health 20, no. 3: 2544. https://doi.org/10.3390/ijerph20032544

APA Style

Morales Arteaga, J. F., Zupanc, M., Dular, M., Lestan, D., & Kaurin, A. (2023). Removal of Toxic Metals from Sewage Sludge by Acid Hydrolysis Coupled with EDTA Washing in a Closed-Loop Process. International Journal of Environmental Research and Public Health, 20(3), 2544. https://doi.org/10.3390/ijerph20032544

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