Papers by Keyword: Electron Donor

Abstract: Effects of different electron donors (acetate and hydrogen), acetate and perchlorate concentrations on microbial perchlorate reduction in groundwater were studied. The results showed that acetate and hydrogen addition as an electron donor can significantly improve perchlorate removal efficiency while a longer period was observed for hydrogen (15 d) than for acetate (8 d). The optical ratio of electron donor (acetate)-to-electron acceptor (perchlorate) was approximately 1.65 mg COD mg perchlorate-1. The highest specific reduction rate of perchlorate was achieved at the acetate-to-perchlorate ratio of 3.80 mg COD mg perchlorate-1. The perchlorate reduction rates corresponded well to the theoretical values calculated by the Monod equation and the parameters of Ks and Vm were determined to be 15.6 mg L-1 and 0.26 d-1, respectively.

Abstract: In this study, a trichloroethylene (TCE)-spill site was selected to assess the feasibility of enhanced in situ anaerobic bioremediation of TCE-contaminated groundwater using hydrogen as the electron donor produced from nanoscale zero-valent iron (nZVI). Results of hydrogen production experiments show that nZVI had a good efficiency on hydrogen production. Results of microcosm study show that indigenous microorganisms were capable of degrading TCE under anaerobic reductive dechlorinating conditions. Compared to the live control and autoclaved control microcosms, microcosms with hydrogen addition significantly enhanced the TCE removal rates. Results imply that nZVI can be applied as the source of hydrogen to bioremediate TCE-contaminated groundwater under anaerobic conditions. Except for the biotic mechanism, the supplied nZVI can also cause the TCE degradation via abiotic mechanism through oxidation-reduction process. For field application, if proper doses of iron nanoparticles can be applied in the mid- or downgradient areas, both chemical and biological mechanisms can enhance the removal of the contaminants and their byproducts. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site. The nZVI treatment scheme would be expected to provide a more cost-effective alternative to remediate chlorinated-solvent contaminated aquifers.

Abstract: The aim of the work was the comparison between a selected reactive mixture containing organic matter for SRB and other electron donors, such as ethanol and polysaccharides. The comparison was performed in order to select the best operating conditions in terms of organic sources for SRB. A continuously operating fixed-bed column was filled with a batch-optimised solid reactive mixture (6% leaves, 9% compost, 3% zero valent iron, 30% silica sand, 30% perlite, 22% limestone) and inoculated by SRB. At steady state 50±10% sulphate abatement was reached and metals were totally removed. Batch tests with ethanol showed the ability of SRB to grow on this substrate efficiently. Experimentation using ethanol was performed using two different column reactors filled with perlite, one inoculated by SRB and the other used as blank. Sulphate abatements of the inoculated column were 70±10% against 10±5% of the blank column. Preliminary batch tests with polysaccharides showed the ability of bacteria to grow on these substrates.