Improving the Biogas Production and Methane Yield in a UASB Reactor with the Addition of Sulfate

Dimitra Theodosi Palimeri, Konstantina Papadopoulou, Apostolos G. Vlyssides and Anestis A. Vlysidis ()
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Dimitra Theodosi Palimeri: School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece
Konstantina Papadopoulou: School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece
Apostolos G. Vlyssides: School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece
Anestis A. Vlysidis: School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece

Sustainability, 2023, vol. 15, issue 20, 1-21

Abstract: Sulfate is of great importance in anaerobic digestion as its addition can help control the microbial community. In this study, the effect of sulfuric acid addition on the performance of a UASB reactor fed with hydrolyzed starch was investigated. The total organic carbon (TOC), Fe, SO 4 2− removal and methane production were monitored under various chemical oxygen demand (COD) to SO 4 2− ratios, hydraulic retention times (HRTs) and organic loading rates (OLRs). When the HRT was 16 h, and the OLR was equal to 2 g COD/L UASB -day, methane production was 0.24 L CH 4 /L UASB -day. After the addition of sulfuric acid, TOC removal reached 95%, and the population of Ruminococcus sp. that utilize soluble carbohydrates increased by 19.7%. Nitrogen removal was less than 25%, while the population of Ignavibacterium sp. accounted for 2.3%. When the HRT, OLR and COD/SO 4 2− ratios were equal to 16 h, 2 g COD/L UASB -d and 3.72, respectively, methane production was 0.267 L CH 4 /L UASB -day. When the OLR increased to 5.94 g, the COD/L UASB -day and COD/SO 4 2− ratios were equal to 12.5, and methane production was three times higher (0.84 L CH 4 /L UASB -day), with a methane content in the produced biogas greater than 70% due to the increased amount of Methanosaeta sp. and direct interspecies electron transfer. Sulfate addition increased the relative abundance of Desulfovibrio sp., accounting for 9.9% and an iron accumulation exceeding 98.0%. This study indicates that appropriate sulfate concentrations in the feed in combination with the presence of iron in the UASB lead to enhanced methane yields.

Keywords: anaerobic digestion; UASB reactor; COD/SO 4 2− ratio; methane production; microbial diversity; sulfate reduction; sulfate-rich substrate (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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