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

Morales Arteaga, Juan Francisco (author), Zupanc, Mojca (author), Dular, Matevž (author), Leštan, Domen (author), Kaurin, Anela (author)

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.

• Language: English
• Keywords: sewage sludge, toxic metals, EDTA, hydrolysis, microwaves, cavitation, phosphorus
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2023
• Number of pages: 13 str.
• Numbering: Vol. 20, iss. 3, art. 2544
• PID: 20.500.12556/RUL-144176
• UDC: 502.1
• ISSN on article: 1660-4601
• DOI: 10.3390/ijerph20032544
• COBISS.SI-ID: 140480003
• Publication date in RUL: 02.02.2023

Record is a part of a journal

• Title: International journal of environmental research and public health
• Shortened title: Int. j. environ. res. public health
• Publisher: MDPI
• ISSN: 1660-4601
• COBISS.SI-ID: 1818965

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: blato iz čistilnih naprav, strupene kovine, EDTA, čiščenje, mikrovalovna pečica, kavitacija, fosfor

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