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Open AccessArticle

Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios

1
Department of Civil, Energy, Environmental and Materials Engineering, Mediterranean University of Reggio Calabria, Via Graziella, loc. Feo di Vito, I-89122 Reggio Calabria, Italy
2
Department of Environmental Engineering, University of Calabria, via P. Bucci, 87036 Rende (CS), Italy
*
Authors to whom correspondence should be addressed.
Academic Editors: Constantinos V. Chrysikopoulos and Maria Cristina Collivignarelli
Water 2021, 13(4), 391; https://doi.org/10.3390/w13040391
Received: 4 January 2021 / Revised: 27 January 2021 / Accepted: 28 January 2021 / Published: 3 February 2021
Anaerobic digestion (AD) represents a suitable option for the management of the waste-activated sludge (WAS) produced in municipal wastewater treatment plants. Nevertheless, due to its complex characteristics, WAS is often barely degradable under conventional anaerobic processes. The use of conductive materials during AD provides a promising route for enhancing WAS digestion, through the effects of direct inter-species electron transfer (DIET). The present paper aims to evaluate the effects of the addition of four different materials—granular activated carbon (GAC), granular iron, and aluminium and steel scrap powders—in semi-continuous lab-scale reactors under very high volatile fatty acids-to-alkalinity ratios. In particular, the use of metallic aluminium in WAS digestion was investigated for the first time and compared to the other materials. The AD of WAS without the addition of conductive materials was impossible, while the use of steel powder and zero-valent iron is shown not to improve the digestion process in a satisfactory way. On the contrary, both GAC and Al allow for effective WAS degradation. At stable conditions, methane yields of about 230 NmLCH4/gVS and 212 NmLCH4/gVS are recorded for GAC- and Al-amended reactors, respectively. These two materials are the most promising in sustaining WAS AD through DIET also in case of unbalanced volatile fatty acids-to-alkalinity ratios. View Full-Text
Keywords: aluminium; alkalinity; anaerobic digestion; granular activated carbon; waste-activated sludge; zero-valent iron aluminium; alkalinity; anaerobic digestion; granular activated carbon; waste-activated sludge; zero-valent iron
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MDPI and ACS Style

Calabrò, P.S.; Fazzino, F.; Limonti, C.; Siciliano, A. Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios. Water 2021, 13, 391. https://doi.org/10.3390/w13040391

AMA Style

Calabrò PS, Fazzino F, Limonti C, Siciliano A. Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios. Water. 2021; 13(4):391. https://doi.org/10.3390/w13040391

Chicago/Turabian Style

Calabrò, Paolo S.; Fazzino, Filippo; Limonti, Carlo; Siciliano, Alessio. 2021. "Enhancement of Anaerobic Digestion of Waste-Activated Sludge by Conductive Materials under High Volatile Fatty Acids-to-Alkalinity Ratios" Water 13, no. 4: 391. https://doi.org/10.3390/w13040391

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