Waterjet Injection Technology to Enhance Bioremediation of Chlorinated Solvents Contamination

This 2-year pilot-scale study aimed to remediate chlorinated volatile organic compounds (cVOCs) in a low-permeability aquifer, with trichloroethylene (TCE) and 1,2-dichloroethane (1,2-DCA) as the target contaminants. To overcome the limitations of conventional amendment delivery methods, a high-pressure waterjet injection technique was applied to create fine circular slots within the aquifer, enabling the directional delivery of electron donor substrates and improving their distribution in low-permeability zones. The efficiency of substrate transport and reaction was evaluated using time-lapse cross-hole electrical resistivity tomography (TL-CHERT) and groundwater monitoring data, including total organic carbon (TOC), chloride, and metabolic by-products such as ethene and methane. Prior to injection, the aquifer at the site was under aerobic conditions with low organic carbon content, indicating insufficient electron donor availability and unfavorable conditions for reductive dechlorination. After waterjet injection, geochemical results indicated that reducing conditions were rapidly established, accompanied by the gradual depletion of dissolved electron acceptors. As anaerobic conditions developed, concentrations of TCE and 1,2-DCA decreased to below Taiwan's Groundwater Pollution Control Standards (0.05 mg/L) within 1 month, with no rebound observed during the subsequent monitoring period. In addition, the formation and subsequent transformation of intermediate dechlorination products, along with the detection of ethene and methane, further confirmed the ongoing reductive dechlorination process. Overall, these results demonstrate that waterjet injection is a robust and practical approach for delivering amendments in heterogeneous, low-permeability formations.