Pilot-scale Study on Enhanced In-situ Anaerobic Bioremediation of Chlorinated Hydrocarbon-Contaminated Groundwater in a Low-Permeability Bedrock Fracture Zone
Chlorinated aliphatic hydrocarbons (CAHs) are prevalent groundwater contaminants at industrial sites in China. This pilot-scale study evaluated in-situ anaerobic bioremediation of CAHs-contaminated groundwater in a low-permeability bedrock fracture zone at depths up to 40 m. A self-developed anaerobic dechlorinating culture (BS-1), containing Dehalococcoides, Desulfitobacterium, and Dehalogenimonas, was injected alongside carbon sources (sodium citrate and emulsified vegetable oil) and nutrients. Pressurized nitrogen gas injection enhanced the distribution of amendments, achieving a radius of influence of 5.0 m. Over 399 days of monitoring, the combined use of slow-release and soluble carbon sources maintained anaerobic conditions (ORP < -100 mV) for over one year, providing sustained electron donors. The emulsified vegetable oil reduced injection frequency and operational costs. The BS-1 culture effectively dechlorinated vinyl chloride, cis-1,2-dichloroethylene, trichloroethylene, and chloroform, achieving removal efficiencies exceeding 95%. At times, groundwater quality met the Class IV standard of GB/T 14848-2017. This study demonstrates a green, economical, and effective solution for CAH-contaminated site remediation, with significant engineering application potential.