Molybdate to prevent the formation of sulfide during the process of biogas production

Abstract

The process of anaerobic digestion producing biogas is an eco-friendly energy source that promotes recycling from waste biomass such as food chain residues, wet waste, wastewater. In this study, we focused on the problem of the sulfide (H2S) produced by the sulfate-reducing bacteria (SRB) in the presence of sulfate residues. This byproduct is dangerous for human health and an issue due to the highly corrosive effect on metallic components. To this purpose, the Molybdate, a sulfate analog, known in the literature to inhibit SRBs by blocking the first enzyme of the metabolic pathway of anaerobic respiration, was applied. The experiments carried out showed that a concentration of 0.3 mM of molybdate was enough to inhibit the SRB in a complex environment of the anaerobically digested sludge (ADS) took from a real biogas producing bioreactor. During the study, we observed the importance of the sulfate concentration sulfate in the system. Indeed, the production of sulfide was stopped only under the threshold ratio value of 1:10 (molybdate: sulfate). In the short term, the addition of molybdate did not alter the production and quality (% of methane) of the biogas, nor the anaerobic microbial community, including SRB population itself.

Molybdate delays sulphide formation in the sediment and transfer to the bulk liquid in a model shrimp pond

“…A higher absolute abundance of the phylum Delsufobacterota, containing several SRB, was detected in molybdate treated samples, despite the fact that mitigation of sulphide production was observed. A similar trend was observed in an earlier study (Tenti et al, 2019), where SRB counts in all samples from a lab-scale anaerobic digester, were similar with or without molybdate, when molybdate concentration was lower than 1.2 mM. In this study, the detection of SRB through 16S rRNA gene amplicon sequencing showed a relative increase of SRB, but did not provide any information on their activity or absolute abundance.…”

Assessment of the Biogenic Souring in Oil Reservoirs Under Secondary and Tertiary Oil Recovery

“…Originally proposed by Peck [100], molybdate has been studied as SRB inhibitor in recent years for relevant technical applications such as in biogas generation [101] or within the oil and gas industry [4,27]. As an analogue to the sulfate ion, molybdate targets the first step of microbial dissimilatory sulfate reduction very specifically, the sulfurization of ATP to adenosine-5 -phosphosulfate (APS) under the release of pyrophosphate.…”

Assessment of the Biogenic Souring in Oil Reservoirs under Secondary and Tertiary Oil Recovery

“…Originally proposed by Peck [110], molybdate has been studied as an SRB inhibitor in recent years for relevant technical applications such as in biogas generation [111] or within the oil and gas industry [4,27]. As an analogue to the sulfate ion, molybdate targets the first step of microbial dissimilatory sulfate reduction; very specifically, it targets the sulfurization of ATP to adenosine-5 -phosphosulfate (APS) under the release of pyrophosphate.…”

“…The involved enzyme, ATP sulfurylase or sulfate adenylyl transferase, is unable to discriminate between sulfate and molybdate. The resulting molybdate intermediate is not stable, leading to gradual depletion of intracellular ATP and eventually to cell lysis, after which the molybdate is still available for further reactions [110][111][112]. Despite this catalytic mode of action, its low toxicity, and its low environmental hazard class, molybdate has not been employed in the petroleum industry widely.…”