文摘
Batch microcosms were setup to determine the impact of different sized zero valent iron (Fep>0p>) particles on microbial sulfate reduction during the in situ bio-precipitation of metals. The microcosms were constructed with aquifer sediment and groundwater from a low pH (3.1), heavy-metal contaminated aquifer. Nano (nFep>0p>), micro (mFep>0p>) and granular (gFep>0p>) sized Fep>0p> particles were added to separate microcosms. Additionally, selected microcosms were also amended with glycerol as a C-source for sulfate-reducing bacteria. In addition to metal removal, Fep>0p> in microcosms also raised the pH from 3.1 to 6.5, and decreased the oxidation redox potential from initial values of 249 to 鈭?26聽mV, providing more favorable conditions for microbial sulfate reduction. mFep>0p> and gFep>0p> in combination with glycerol were found to enhance microbial sulfate reduction. However, no sulfate reduction occurred in the controls without Fep>0p> or in the microcosm amended with nFep>0p>. A separate dose test confirmed the inhibition for sulfate reduction in presence of nFep>0p>. Hydrogen produced by Fep>0p> was not capable of supporting microbial sulfate reduction as a lone electron donor in this study. Microbial analysis revealed that the addition of Fep>0p> and glycerol shifted the microbial community towards Desulfosporosinus sp. from a population initially dominated by low pH and metal-resisting Acidithiobacillus ferrooxidans.