The Remediation of Groundwater Contaminated with High Concentrations of Sulfates and Chloroethenes Using Ferrous-Based Chemical Agents Combined with Bioaugmentation Technology

Chlorinated organic compounds, such as trichloroethylene (TCE), are a class of highly recalcitrantenvironmental pollutants, frequently detected in Taiwan's groundwater and posing significant remediationchallenges. Currently, the deregulation rate of contaminated sites in the country is less than 20%. In recentyears, improper discharges from industrial activities, particularly in fossil fuel usage, mining, and metalprocessing, have exacerbated the issue of sulfate accumulation. Notably, in many industrialized nations,TCE-contaminated sites are often associated with high concentrations of sulfate, with levels ranging from0.2 mM to 30 mM. However, the direct effects of sulfate on the TCE degradation process remain unclearin past studies, leading to the frequent neglect of such coexisting pollution problems in remediationstrategies. To address these challenges, this project proposes an innovative remediation strategy thatcombines ferrous agents with bio-agents to simultaneously tackle the co-contamination of sulfate andTCE. This approach not only effectively reduces the inhibitory effects of hydrogen sulfide ondehalococcoides but also promotes the formation of iron sulfide (FeS), thereby enhancing the abioticdegradation of TCE. Under site conditions where TCE and sulfate coexist, the synergistic actions ofsulfate-reducing bacteria and dehalococcoides, supplemented by the application of ferrous agents, enablethe simultaneous removal of both TCE and sulfate. Moreover, the hydrogen sulfide produced duringsulfate reduction reacts with ferrous agents to generate FeS, further facilitating the abiotic degradation ofchlorinated ethenes (CEs), achieving a synergistic remediation effect. This remediation strategy integratesbiological and abiotic mechanisms and is expected to enhance remediation efficiency, shorten theremediation period, and effectively avoid the risks of secondary pollution associated with over-relianceon chemical remediation technologies. This method holds great potential for future applications,contributing to the sustainable restoration of contaminated sites and providing valuable insights foraddressing similar environmental issues.