Long-term effectiveness and sustainability of EHC remediation in carbon tetrachloride-contaminated groundwater: Mechanistic understanding and practical applications

The presence of carbon tetrachloride in groundwater raises concerns for human health and the environment. Thus, there is an urgent need for a faster and more efficient groundwater remediation method. Our study found that the EHC remedial agent can achieve promising pilot remediation results quickly, as demonstrated in laboratory tests. During the pilot test, the contaminated groundwater was subjected to injection with the EHC remedial agent using in -situ high-pressure rotary jet technology. It was observed that indicators such as alkalinity and SO42 can signify the occurrence of biological reduction, with the presence of ZVI significantly shortening the beginning time of biological action within the EHC. The pilot test results reveal that the initial four days following the injection of the EHC witnessed only chemical reduction, with chemical and biological reduction coexisting from day 4 to day 45. Post the 45-day mark, the removal of contaminants solely relied on biological reduction. While chemical reduction displayed a rapid rate but limited duration, insufficient for ensuring longterm effectiveness in the remediation process, bioremediation offered sustained efficacy for continuous contaminant reduction. These findings signify a more eco-friendly and efficient approach to groundwater remediation, offering both human health and environmental benefits.