Simultaneous dissimilatory reduction of Cr(Ⅵ)and nitrate by Shewanella oneidensis MR-1 in a low-permeability groundwater zone
Cr(Ⅵ)and nitrate were common contaminants in groundwater,which can be transported into low permeability zones thus the remediation issues was ignored.Shewanella oneidensis MR-1 was used to reduce both Cr(Ⅵ)and nitrate in batch and heterogeneous column experiments.Results from batch experiments showed that Cr(Ⅵ)reduction was mainly depended on initial biomass concentration,but was hardly affected by concentrations of nitrate and lactate.On the contrary,nitrate reduction was significantly inhibited by Cr(Ⅵ).The first-order reduction rate constant of nitrate reduction decreased from 0.635h-1 to 0.164h-1 when Cr(Ⅵ)concentration increased from 0 to 0.02mmol/L.At the same time,lactate oxidation rate was also inhibited by high Cr(Ⅵ)concentration,which was possible due to the metabolism of Shewanella oneidensis MR-1 was affect by Cr(Ⅵ)toxicity.In the column experiment,when the influent Cr(Ⅵ)concentration was ≤5mg/L(about 0.1mmol/L),it could be completely removed in 15 days,and about 60％of nitrate was reduced correspondingly.When Cr(Ⅵ)concentration increased to 10mg/L(about 0.2mmol/L),about 40％Cr(Ⅵ)and 50％nitrate were reduced,respectively.The reduction products trapped within the column for Cr(Ⅵ)and nitrate were Cr(OH)3 and ammonia,respectively.
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