Impact of solid content on hydrothermal pretreatment of municipal sludge prior to fermentation and anaerobic digestion

Farokh Laqa Kakar; Steven N Liss; Elsayed Elbeshbishy

doi:10.1016/j.chemosphere.2022.136363

Impact of solid content on hydrothermal pretreatment of municipal sludge prior to fermentation and anaerobic digestion

Chemosphere. 2022 Dec;308(Pt 3):136363. doi: 10.1016/j.chemosphere.2022.136363. Epub 2022 Sep 7.

Authors

Farokh Laqa Kakar¹, Steven N Liss², Elsayed Elbeshbishy³

Affiliations

¹ Environmental Research Group for Resource Recovery, Department of Civil Engineering, Faculty of Engineering, Architecture and Science, Ryerson University, 350 Victoria Street, Toronto, Ontario, M5B 2K3, Canada.
² Department of Chemistry and Biology, Faculty of Science, Ryerson University, 350 Victoria Street, Toronto, Ontario, M5B 2K3, Canada; School of Environmental Studies, Queen's University, Kingston, ON, K7L 3N6, Canada; Department of Microbiology, Stellenbosch University, Private Bag, XI, Matieland, 7602, Stellenbosch, South Africa.
³ Environmental Research Group for Resource Recovery, Department of Civil Engineering, Faculty of Engineering, Architecture and Science, Ryerson University, 350 Victoria Street, Toronto, Ontario, M5B 2K3, Canada. Electronic address: elsayed.elbeshbishy@ryerson.ca.

PMID: 36087725
DOI: 10.1016/j.chemosphere.2022.136363

Abstract

This study investigated the impact of the solid sludge content concentrations (SC) on hydrothermal pretreatment (HTP) before fermentation and anaerobic digestion. Five different SC of 3.5%, 7%, 10%, 12%, and 16% were investigated in two different scenarios. The first scenario entailed using only the pretreated samples as substrates, whereas in scenario two, the substrates included pretreated samples combined with the supernatant. Results revealed that the highest overall pCOD solubilization (considering HTP and fermentation) of 64% was achieved for the sample with 12% SC combined with supernatant. The maximum volatile fatty acids production of 2.8 g COD/L occurred with 10% SC without supernatant. The maximum methane yield of 291 mL CH₄/g VSS added was attained at 7% SC without supernatant. Furthermore, the results indicated that increasing the SC beyond 7% in scenario 1 and 10% in scenario two led to a decrease in methane yield. Additionally, optimizing for all desired endpoints may be difficult, and there are limits on the increase in SC concerning methane production.

Keywords: Anaerobic digestion; Fermentation; Hydrothermal pre-treatment; Solid content; Volatile fatty acids.

MeSH terms

Anaerobiosis
Bioreactors
Fatty Acids, Volatile
Fermentation
Methane*
Sewage* / chemistry

Substances

Fatty Acids, Volatile
Sewage
Methane