Removal of toxic metals from sewage sludge by EDTA in a closed-loop washing process

Morales Arteaga, Juan Francisco (author), Kaurin, Anela (author), Leštan, Domen (author)

Sewage sludge (SS) is a potential resource for P and other nutrients, but often contaminated with metals. SS containing Pb-102, Zn-968, Cu-267, Cr-101, Mn-222, and Fe-8374 mg kg$^{-1}$ was washed in a batch process for 1 h with a recycled washing solution containing 50 mmol L$^{-1}$ of recycled EDTA and 50 mmol L$^{-1}$ H$_2$SO$_4$, solid/liquid ratio 1/7 (w/V). After solid/liquid separation, the washed SS was further rinsed 3-times with cleansed recycled solutions. EDTA and process solutions were recycled/cleansed in a pH gradient of 12.5–2.0 imposed by addition of CaO and H$_2$SO$_4$ (the ReSoil® method). EDTA, recycled as ineffective Ca-EDTA, was activated by capturing Ca with H$_2$SO$_4$. The process was closed-looped, no wastewater was generated, solid waste was centrifuged away. 10 consecutive SS washing batches preserved the quality of the process solutions. Metals were mainly removed from the SS organic fraction, the average removal was Pb-35, Zn-59, Cu-60, Cr-19, Mn-25, and Fe-1%. Washing reduced the leachability of Cu and Cr from SS by 13.4 and 3.5 times, but increased the leachability of Pb, Zn, Mn, and Fe by 2.5, 3.8, 1.9, and 1.6 times, respectively. Metal concentrations in the leachates were below the limits stipulated as hazardous. The content of accessible P and K in washed SS decreased by 24 and 45%, and the total N decreased by 10%. Overall, the results prove the feasibility of the novel SS washing process.

• Language: English
• Keywords: potential toxic elements, toxic metals, soil washing, chelating agents, contaminated soil, EDTA, toxic emissions, phosphorus, sewage sludge
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: 9 str.
• Numbering: Vol. 307, pt. 2, art. 135917
• PID: 20.500.12556/RUL-140919
• UDC: 502.1
• ISSN on article: 0045-6535
• DOI: 10.1016/j.chemosphere.2022.135917
• COBISS.SI-ID: 122208003
• Publication date in RUL: 21.09.2022

Record is a part of a journal

• Title: Chemosphere
• Shortened title: Chemosphere
• Publisher: Elsevier
• ISSN: 0045-6535
• COBISS.SI-ID: 25213696

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: toksične kovine, potencialno škodljivi elementi, EDTA, pranje tal, onesnaženost tal, remediacija tal

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: J7-2601
• Name: Metoda dekontaminacije aktivnih blat in njihovih produktov za njihovo trajnostno uporabo kot fosfatna gnojila

• Funder: ARRS - Slovenian Research Agency
• Project number: P4-0085
• Name: Agroekosistemi