Combination of nanoscale-zero-valent iron and organic sub-strate stimulation for efficient remediation of co-mingled plume contaminated with Cr(VI) and chlorinated solvents
Abstract
Chromium and chlorinated ethenes represent typical toxic pollutants that cause pollution of groundwater and soil due to their frequent industrial application. The present work reports results of 1-year pilot-remediation in-situ study dealing with a co-mingled plume containing the above-mentioned pollutants.
The successful decontamination was achieved by the sequential use of nanoscale zerovalent iron (nZVI) particles and in situ biotic reduction supported by whey injection. The results revealed that nZVI was efficient toward Cr(VI) by itself and completely removed it from the groundwater (99%) and the subsequent application of whey resulted in a high removal of chlorinated ethenes (97-99%).
The persistence of the reducing conditions after the depletion of the organic substrates indicated complementarity between nZVI and the whey phases. The subsequent application of whey phase assisted the microbial regeneration of the spent nZVI by promoting its reduction into Fe(II), which further supported remediation conditions at the site.
Illumina sequencing and the detection of functional genes documented a development in the reducing microbes (iron-reducing, sulfate-reducing and chlororespiring bacteria) that benefited under the conditions of the site and that was probably responsible for the high dechlorination and/or Cr(VI) reduction. The results of this study demonstrate the feasibility and high efficiency of the combined nano-biotechnological approach for the removal of Cr(VI) and chlorinated ethenes from the groundwater.