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Groundwater at trichloroethylene (TCE)-contaminated sites lacks electron donors, which prolongs TCE’s natural attenuation process and delays treatment. Although adding electron donors, such as emulsified oil, accelerates TCE degradation, it also causes the accumulation of hazardous metabolites such as dichloroethylene (DCE) and vinyl chloride (VC). This study combined in situ chemical reduction using organo-iron compounds with enhanced in situ bioremediation using emulsified oil to accelerate TCE removal and minimize the accumulation of DCE and VC in groundwater. A self-made soybean oil emulsion (SOE) was used as the electron donor and was added to liquid ferrous lactate (FL), the chemical reductant. The combined in situ chemical reduction and enhanced in situ bioremediation achieved favorable results in a laboratory microcosm test and in an in situ biological field pilot test. Both tests revealed that SOE+FL accelerated TCE degradation and minimized the accumulation of DCE and VC to a greater extent than SOE alone after 160 days of observation. When FL was added in the microcosm test, the pH value decreased from 6.0 to 5.5, however, during the in situ biological pilot test, the on-site groundwater pH value did not exhibit obvious changes. Given the geology of the in situ pilot test site, the SOE+FL solution that was injected underground continued to be released for at least 90 days, suggesting that the solution’s radius of influence was at least 5 m.

Several remediation technologies were evaluated in this study to efficiently break down lubricant in contaminated soil, including chemical oxidation, bioremediation, and the combination of chemical oxidation and bioremediation. The chemical oxidation batch experiment results indicated that when soil pH was acidified to 3.0, traditional Fenton's oxidation most effectively removed lubricant in contaminated soil. However, this method may cause permanent damage to the ecosystem since it requires acidic soil conditions. Further experimentation showed that by adding citric acid to traditional Fenton's oxidation, this modified Fenton's process oxidized the lubricant even more efficiently, by forming an effective chelation and preventing the production of ferric oxide precipitates, all under neutral soil conditions. In the bioremediation tests, results showed that lubricant degradation efficiencies improved by adding peptone and glutamate salt, since they served as nutrients for the soil microbes. Overall, the combination of a 56 d biopile with ammonium chloride and monosodium glutamate, followed by a modified Fenton's oxidation, was found to be the optimal degradation approach in lubricant-contaminated soil, with a promising 99.2% removal efficiency for an initial concentration of 10,000 mg kg−1 of lubricant.