Abstract
Tetrachloroethene (PCE) is one of the commonly found toxic chemicals in chlorinated-solvent contaminated groundwater. The objective of this study was to evaluate the effectiveness of enhanced bioremediation of PCE-contaminated groundwater with the supplement of nanoscale zero-valent iron (nZVI) contained long-lasting emulsified colloidal substrate (LECS) at a PCE-contaminated site. Approximately 50L of LECS solution was pressured-injected into a remediation well (RW) and groundwater samples were collected from RW, two downgradient monitor wells (MWs), a control well, and a background well periodically for analyses. Injected LECS caused a rapid increase of the total organic carbon (TOC) concentration (up to 874mg/L), and the increased TOC resulted in the transformation of the oxidation-reduction potential from aerobic to anaerobic stage. The pH was maintained in neutral due to the release of hydroxide ion after the oxidation of nZVI. Biodegradative reductive dechlorination of PCE was significantly enhanced, and PCE dropped from 0.5 to 0.01mg/L after 130days of operation. PCE dechlorination byproducts were also observed in downgradient MWs. Real-time polymerase chain reaction (PCR) results show that the populations of Dehalococcoides spp. (DHC) and Desulfitobacterium spp. (DSB) increased from 2×103 to 1.2×107 and from 1×103 to 7.4×106cell/L after 60days of operation in RW, respectively. DHC population was mainly composed of DHC in Victoria and Pinellas subgroups. Results demonstrate that supplement of LECS in PCE-polluted groundwater can effectively contain the PCE plume and accelerate the PCE dechlorinating rate under anaerobic conditions.
Published Version
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