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

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

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

blato iz čistilnih naprav;strupene kovine;EDTA;čiščenje;mikrovalovna pečica;kavitacija;fosfor;sewage sludge;toxic metals;hydrolysis;microwaves;cavitation;phosphorus;

Data

Language:	English
Year of publishing:	2023
Typology:	1.01 - Original Scientific Article
Organization:	UL BF - Biotechnical Faculty
UDC:	502.1
COBISS:	140480003
ISSN:	1660-4601
Views:	30
Downloads:	5
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	blato iz čistilnih naprav;strupene kovine;EDTA;čiščenje;mikrovalovna pečica;kavitacija;fosfor;
Type (COBISS):	Article
Pages:	13 str.
Volume:	ǂVol. ǂ20
Issue:	ǂiss. ǂ3, art. 2544
Chronology:	2023
DOI:	10.3390/ijerph20032544
ID:	17916532