Genome-resolved metagenomic insight into vanadate and ammonium elimination in sulfur-based autotrophic biosystem

The extensive use of ammonium (NH4+) as a precipitant in non-ferrous metallurgy, such as vanadium production, leads to the co-occurrence of toxic heavy metals and NH4+-N in the resultant wastewater. Finding an efficient and cost-effective method for simultaneously removing vanadate [V(V)] and NH4+-N in a single step has remained unexplored. This study presents a novel approach by establishing the synchronous bio-elimination of V(V) and NH4+-N in a sulfur (S0)-based autotrophic system. Remarkably, 96.7 ± 2.2 % of V(V) and 99.4 ± 0.8 % of NH4+-N were successfully removed within 24 hrs. V(V) was transformed into V(IV) precipitates, while S0 was oxidized into sulfate, achieving complete nitrogen removal. Fifty-six genomes were retrieved and constructed from metagenomic binning, unveiling symbiotic interactions involved in sulfur, nitrogen, and vanadium transformation. With the annotation of functional genes (e.g., nar, nir, nap, nor, nos, sox, sor, dsr) and multi-heme c-type cytochromes, it was identified that V(V) reduction and denitrification, coupled with S0 oxidation, were mediated by species such as Sulfuricurvum sp., Achromobacter sp., and Thiomonas sp.. Meanwhile, NH4+ oxidation was accomplished by Anaeromyxobacter sp.. Furthermore, autotrophs harnessed inorganic carbon through the Calvin-Benson-Bassham and Wood-Ljungdahl pathways to synthesize organic intermediates, which were subsequently consumed by heterotrophic organisms (e.g., Pseudomonas sp.) to facilitate V(V) reduction and denitrification. The quantification of transcripts associated with genes responsible for V and N metabolism provided additional evidence of these metabolic pathways' existence. This study offers a sustainable and environmentally friendly strategy for mitigating the adverse environmental impacts of vanadium production wastewater.