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Open AccessArticle

Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter

1
Department Polytechnic of Engineering and Architecture, University of Udine, Via del Cotonificio 108, 33100 Udine, Italy
2
Department of Agricultural, Food, Environmental and Animal Sciences (DI4A), University of Udine, Via delle Scienze 206, 33100 Udine, Italy
*
Author to whom correspondence should be addressed.
Academic Editor: Marco Pellegrini
Water 2021, 13(7), 933; https://doi.org/10.3390/w13070933
Received: 1 March 2021 / Revised: 23 March 2021 / Accepted: 25 March 2021 / Published: 29 March 2021
(This article belongs to the Special Issue Treatment and Reuse of Sewage Sludge)
Land application of sewage sludge on agricultural soils can be sustainable only if pollutant contents and organic matter quality meet the requirements imposed by minimization of environmental risks. This study investigated the degradation of linear alkylbenzene sulfonates (LAS) and extractable organic halogens (EOX) and the formation of humic substances (HS) during the thickening and storage phases of sewage sludge treatment. Changes in spectroscopic properties (UV-Vis, FT-IR, and excitation-emission matrix (EEM) fluorescence) of HS were also evaluated to assess the occurrence of biological activities during these curing phases of sewage sludge (SS). Humic acids (HA), fulvic acids (FA), EOX, and LAS were extracted from sewage sludge sampled from four municipal wastewater treatment plants of different size and treatment sequence, before and after 90 days of aerobic or anaerobic storage. During storage, the loss of organic C in the SS ranged from almost null to 31%. No significant changes of FA were registered, whereas HA increased in almost all samples, up to 30%. The amount of humic substances synthesized during storage correlated with the percentage of C lost. Spectroscopic changes of FA and HA showed an increase in their aromaticity, with a corresponding decrease in the aliphatic contribution. These changes show the improved agronomical quality of SS. LAS decreased during storage up to 30%, surprisingly more under anaerobic than aerobic conditions, whereas EOX decreased significantly in all samples, even up to 81%. In conclusion, although storage may be normally considered not influencing the quality of SS, their organic matter quality improved and contamination decreased during 90 days of storage, whatever the conditions of oxygen availability applied. View Full-Text
Keywords: sewage sludge reuse; EOX; LAS; humic substances; land use sewage sludge reuse; EOX; LAS; humic substances; land use
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MDPI and ACS Style

Khakbaz, A.; Goi, D.; Bravo, C.; Contin, M. Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter. Water 2021, 13, 933. https://doi.org/10.3390/w13070933

AMA Style

Khakbaz A, Goi D, Bravo C, Contin M. Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter. Water. 2021; 13(7):933. https://doi.org/10.3390/w13070933

Chicago/Turabian Style

Khakbaz, Ali; Goi, Daniele; Bravo, Carlo; Contin, Marco. 2021. "Thickening and Storage of Sewage Sludge Contribute to the Degradation of LAS and EOX and the Humification of Organic Matter" Water 13, no. 7: 933. https://doi.org/10.3390/w13070933

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