Development of a Ganoderma lucidum bioreactor for dichlorodiphenyltrichloroethane contaminated soil treatment

Dichlorodiphenyltrichloroethane (DDT) and its transformation products (collectively referred to as DDX) remain persistent contaminants in Swedish soils despite being banned over 50 years ago. Their partitioning to soil organic matter limits bioavailability and hampers bioremediation efforts. This study created and evaluated a novel pilot bench-scale bioreactor system, which integrates surfactant-assisted soil washing with fungal degradation of DDX for the treatment of aged, contaminated soil. White-rot fungus Ganoderma lucidum was investigated for its ability to degrade DDT in a pre-trial, due to its production of high redox potential extracellular ligninolytic enzymes. In a mycelial suspension, G. lucidum degraded 73 ± 6% of ∑DDX within 10 days. A prototype trickle-bed bioreactor was then developed in which Tween 80 was continuously circulated through contaminated soil to mobilize DDX into solution before contact with G. lucidum colonized woodchips. After 28 days of treatment and a parallel control, ∑DDX in the soil decreased from 10 500 ± 990 µg to 4 300 ± 610 µg in the fungal treatment compared with 7 600 ± 920 µg in the control. Higher mobilization of DDX to the liquid phase was also observed in the treatment bioreactor. Overall, the integrated system reduced ∑DDX by approximately 45% relative to the control and demonstrated effective coupling of soil washing with fungal degradation. These findings highlight the potential of mycoremediation large-scale systems for the treatment of historically contaminated soils. KEY POINTS: Bench-scale system integrates washing of aged, contaminated soil with fungal degradation of DDT Ganoderma lucidum degraded DDT in liquid culture and pilot bioreactor Surfactant mobilization improved DDT and transformation product availability for fungal treatment.