Pilot-scale Study on Enhanced In-situ Anaerobic Bioremediation of Chlorinated Hydrocarbon-Contaminated Groundwater in a Low-Permeability Bedrock Fracture Zone

• • Pressurized nitrogen gas injection after liquid amendments achieved a radius of influence of 5.0 m in low-permeability bedrock fractures, overcoming mass transfer limitations and ensuring uniform distribution of nutrients and bacteria. • • Combined injection of slow-release (emulsified vegetable oil) and soluble (sodium citrate) carbon sources maintained ORP below -100 mV for over one year, creating sustained anaerobic conditions essential for reductive dechlorination. • • The slow-release carbon source (emulsified vegetable oil) reduced injection frequency, lowering operational costs while providing stable electron donors for dechlorinating bacteria. • • The BS-1 culture achieved >95% removal of vinyl chloride, cis-1,2-dichloroethylene, trichloroethylene, and chloroform via anaerobic reductive dechlorination, with groundwater quality occasionally meeting Class IV of GB/T 14848-2017.