| With the rapid development of economy and industry,heavy metal?vanadium?contaminated groundwater has become a safety hazard of drinking water.The microbial remediation technology of vanadium contamination is considered to be very promising.In this study,the performance of microbial remediation of vanadium contaminated groundwater was investigated with various kinds of inocula.The involved microbes were analyzed.The feasibility of continuous microbial V?V?removal was explored with sawdust used as solid carbon sources.The V?V?reduction mechanism of functional species was also revealed.With the soils sampled from vanadium ore mining areas?vanadium titanomagnetite,stone coal,petroleum associated minerals and uvanite?as inocula,the average V?V?removal efficiencies?60 h?were 92.0%,69.0%,91.0% and 87.1%,respectively.It was indicated that the soils of the vanadium ore mining areas could be used as inocula for the bioremediation of vanadium containing groundwater.The results of microbial community analysis have shown that the genera such as AcidobacteriaceaeSubgroup1uncultured,Bryobacter and Microvirga were enriched,which might contribute to the V?V?removal in the reactors.The health risk assessment results of original soil samples collected from farmland near various vanadium ore mining areas have shown that the hazard quotient?HQ?values were 0.69?vanadium titanomagnetite ore mining area?,3.64?stone coal ore mining area?,0.77?petroleum associated minerals ore mining area?and 0.56?uvanite ore mining area?,respectively.The farmland soil near stone coal ore mining area has posed higher non-carcinogenic risks to the public.The V?V?removal efficiencies?60 h?were ranging from 82.7% to 98.4% with the sampled soils as inocula.Results showed that bacterial communities of bioreactors were dominated by the microbes which could tolerate or reduce toxicities of heavy metals,such as the bacteria from the genera of Ruminococcaceaeincertaesedis,Trichococcus and Comamonas.With anaerobic sludge as inocula and sawdust as solid carbon sources,the removal efficiency of V?V?is about 90.3% in the synthetic groundwater.While in the actual groundwater,the V?V?removal efficiency is around 53.2%.The sawdust could be used as the carbon sources for the bioremediation of vanadium containing groundwater.With the medical stone?4.0 g?and phosphate rock?4.0 g?added,the V?V?removal efficiency in the actual groundwater increased to 82.6%.The addition of medical stone and phosphate rock could strengthen the ability of microbes to remove V?V?.The results of the column experiments with sawdust as carbon sources have shown that the microbes could quickly exert sustained vanadium remediation abilities in the systems inoculated with the domesticated soils from petroleum associated minerals ore mining area and farmland near the uvanite ore mining area.While the system with the domesticated anaerobic sludge as inocula could remove V?V?in the actual groundwater more effectively for a longer time.The results have shown that V?V?could be reduced by Enterococcus faecium,and the reduction of V?V?with the initial concentration from 25.5 to 254.7 mg/L could be realized within 15 d.The microbial reduction rates increased with the increasing initial V?V?concentrations.The results also reflected that the combined removal of V?V?and Cr?VI?could be realized by Enterococcus faecium.The Cr?VI?bioreduction was enhanced with V?V?,while the V?V?reduction was suppressed.Results showed that V?V?was able to be reduced by the crude cell extracts,cell membrane fractions and intracellular soluble substances of Enterococcus faecium.It was suggested that V?V?could be reduced by Enterococcus faecium both inside and outside of the cells.The bioremediation processes of the vanadium contaminated groundwater with various kinds of inocula and the V?V?reduction mechanism were revealed in the study.The obtained results could suggest a theoretical foundation for the remediation of vanadium contaminated groundwater and provide technical support for practical applications. |
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