Rapid isolation of indigenous degraders combined with autochthonous bioaugmentation for in situ remediation of groundwater contaminated with complex organic pollutants: a pilot-scale study.

Organic contamination of groundwater associated with active industrial operations is becoming increasingly prominent. In situ bioremediation is widely considered an environmentally friendly and economically feasible remediation strategy. However, wastewater and solid wastes generated by certain industries, such as pharmaceutical manufacturing, often exhibit highly complex compositions, making the direct application of conventional bioaugmentation to contaminated groundwater challenging. Autochthonous bioaugmentation (ABA) represents a promising alternative approach that relies on the rapid acquisition of efficient indigenous degrading bacteria, although its engineering application potential has not yet been fully validated. In this study, a limiting dilution method for rapid isolation of indigenous degraders was employed using contaminated groundwater as the selective medium. Within one week, 30 potential indigenous chemical oxygen demand (COD) degrading strains were successfully isolated, including a Bacillus strain LH1 capable of rapidly removing COD. Subsequently, an in situ remediation experiment was conducted at the contaminated site. After 12 days, COD removal rates reached 46.4-70.9% at multiple monitoring points, with COD concentrations in several areas declining below the regulatory threshold established for the industrial park. This study presents a successful case of rapidly acquiring indigenous degrading bacteria to support ABA, providing an engineering-ready rapid technical pathway for the bioremediation of groundwater contaminated with complex organic pollutants.