Synchronous microbial vanadium (V) reduction and denitrification in groundwater using hydrogen as the sole electron donor

Abstract

Groundwater co-contaminated by vanadium (V) (V(V)) and nitrate requires efficient remediation to prevent adverse environmental impacts. However, little is known about simultaneous bio-reductions of V(V) and nitrate supported by gaseous electron donors in aquifers. This study is among the first to examine microbial V(V) reduction and denitrification with hydrogen as the sole electron donor. V(V) removal efficiency of 91.0 ± 3.2% was achieved in test bioreactors within 7 d, with synchronous, complete removal of nitrate. V(V) was reduced to V(IV), which precipitated naturally under near-neutral conditions, and nitrate tended to be converted to nitrogen, both of which processes helped to purify the groundwater. Volatile fatty acids (VFAs) were produced from hydrogen oxidation. High-throughput 16S rRNA gene sequencing and metagenomic analyses revealed the evolutionary behavior of microbial communities and functional genes. The genera Dechloromonas and Hydrogenophaga promoted bio-reductions of V(V) and nitrate directly coupled to hydrogen oxidation. Enriched Geobacter and denitrifiers also indicated synergistic mechanism, with VFAs acting as organic carbon sources for heterotrophically functional bacteria while reducing V(V) and nitrate. These findings are likely to be useful in revealing biogeochemical fates of V(V) and nitrate in aquifer and developing technology for removing them simultaneously from groundwater.

Microbial Community Responses to Vanadium Distributions in Mining Geological Environments and Bioremediation Assessment

“…These members of the microbial community accumulated in our study and were also found in the vanadium‐contaminated environment (Cao et al, ). They potentially participate in V(V) reduction because vanadium is a redox‐sensitive metal similar to selenium and chromium (Jiang et al, ). In the vertical soil profile, Acidobacteria that accounted for a large proportion of the microbial population can adapt to vanadium‐polluted environments (Cao et al, ).…”

“…Comparative evaluation of the performance of dissolved organic carbon sources shows that acetate supports highly efficient V(V) bio‐reduction (Liu et al, ). Oxidation of gaseous and solid electron donors, such as hydrogen and elemental sulfur (Jiang et al, ; Zhang, Zhou, et al, ; Zhang, Qui, et al, ), can also be coupled to V(V) bio‐reduction without residual organics. Furthermore, coexisting common electron acceptors in groundwater, such as nitrate and sulfate, can decrease the efficiency of V(V) bio‐reduction since they are more efficient electron acceptors (Liu et al, ).…”

Insights into interactions between vanadium (V) bio-reduction and pentachlorophenol dechlorination in synthetic groundwater

“…Vanadium, a redox-sensitive metal, widely occurring in the Earth's crust, is employed in metallurgy, manufacturing, and petroleum refining industries [2], and is an efficient catalyst in the selective catalytic reduction of nitrogen oxides in exhaust gases [3]. Dissolution of vanadium-rich rocks and anthropogenic activities lead to the presence of vanadium in groundwater [4,5]. For example, mining and smelting processes discharge vanadium into soil, after which vanadium can enter aquifers through infiltration [6].…”

Insights into simultaneous microbial chromium and nitrate reduction: inhibitory effects and molecular mechanisms

“…However, groundwater contaminants are not unique in most cases; concurrent contamination by various oxidized contaminants such as nitrate and chromate is increasingly commonplace . Human activities including electroplating and alloy production have had profound impacts on the discharge of chromium (Cr) into aquifers .…”

“…4 However, groundwater contaminants are not unique in most cases; 7 concurrent contamination by various oxidized contaminants such as nitrate and chromate is increasingly commonplace. 7,8 Human activities including electroplating and alloy production have had profound impacts on the discharge of chromium (Cr) into aquifers. 9 Excessive intake of hexavalent chromate [Cr(VI)] (0.1 mg L −1 of MCL in drinking water proposed by U.S. EPA) can cause carcinogenic, teratogenic and mutagenic effects in animals and humans.…”