Impact of thermal hydrolysis on VFA-based carbon source production from fermentation of sludge and digestate for denitrification: experimentation and upscaling implications.

Autor: Carranza Muñoz A; IVL Swedish Environmental Research Institute, Valhallavägen 81, 114 28 Stockholm, Sweden; Department of Molecular Sciences, Biocenter, Swedish University of Agricultural Sciences (SLU), 756 51 Ultuna-Uppsala, Sweden. Electronic address: andrea.carranza.munoz@ivl.se., Olsson J; The Käppala Association, Södra Kungsvägen 315, 181 66 Lidingö, Sweden., Malovanyy A; IVL Swedish Environmental Research Institute, Valhallavägen 81, 114 28 Stockholm, Sweden., Baresel C; IVL Swedish Environmental Research Institute, Valhallavägen 81, 114 28 Stockholm, Sweden., Machamada-Devaiah N; Department of Industrial Biotechnology, KTH Royal Institute of Technology, Roslagstullsbacken 21, 114 21 Stockholm, Sweden., Schnürer A; Department of Molecular Sciences, Biocenter, Swedish University of Agricultural Sciences (SLU), 756 51 Ultuna-Uppsala, Sweden.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2024 Nov 15; Vol. 266, pp. 122426. Date of Electronic Publication: 2024 Sep 10.
DOI: 10.1016/j.watres.2024.122426
Abstrakt: Stricter nutrient discharge limits at wastewater treatment plants (WWTPs) are increasing the demand for external carbon sources for denitrification, especially at cold temperatures. Production of carbon sources at WWTP by fermentation of sewage sludge often results in low yields of soluble carbon and volatile fatty acids (VFA) and high biogas losses, limiting its feasibility for full-scale application. This study investigated the overall impact of thermal hydrolysis pre-treatment (THP) on the production of VFA for denitrification through the fermentation of municipal sludge and digestate. Fermentation products and yields, denitrification efficiency and potential impacts on methane yield in the downstream process after carbon source separation were evaluated. Fermentation of THP substrates resulted in 37-70 % higher soluble chemical oxygen demand (sCOD) concentrations than fermentation of untreated substrates but did not significantly affect VFA yield after fermentation. Nevertheless, THP had a positive impact on the denitrification rates and on the methane yields of the residual solid fraction in all experiments. Among the different carbon sources tested, the one produced from the fermentation of THP-digestate showed an overall better potential as a carbon source than other substrates (e.g. sludge). It obtained a relatively high carbon solubilisation degree (39 %) and higher concentrations of sCOD (19 g sCOD/L) and VFA (9.8 g VFA COD /L), which resulted in a higher denitrification rate (8.77 mg NOx-N/g VSS∙h). After the separation of the carbon source, the solid phase from this sample produced a methane yield of 101 mL CH 4 /g VS. Furthermore, fermentation of a 50:50 mixture of THP-substrate and raw sludge produced also resulted in a high VFA yield (283 g VFA COD /kg VS in ) and denitrification rate of 8.74 mg NOx-N/g VSS∙h, indicating a potential for reduced treatment volumes. Calculations based on a full-scale WWTP (Käppala, Stockholm) demonstrated that the carbon sources produced could replace fossil-based methanol and meet the nitrogen effluent limit (6 mg/L) despite their ammonium content. Fermentation of 50-63 % of the available sludge at Käppala WWTP in 2028 could produce enough carbon source to replace methanol, with only an 8-20 % reduction in methane production, depending on the production process. Additionally, digestate production would be sufficient to generate 81 % of the required carbon source while also increasing methane production by 5 % if a portion of the solid residues were recirculated to the digester.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2024. Published by Elsevier Ltd.)
Databáze: MEDLINE
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