Gentle remediation options for DDT- and HCH-contaminated soil

Gentle remediation options (GROs) such as vermiremediation have not been applied in Colombian soils with DDT and HCH yet, while bioaugmentation and biostimulation under anaerobic and/or aerobic conditions have been successfully implemented. However, it is important to determine under which of the latter conditions the assessed consortium performs better. This research evaluated vermiremediation and bioaugmentation under anaerobic and/or aerobic conditions, assisted with biostimulation, in a DDT- and HCH-contaminated soil. Bacteria were isolated from the contaminated soil and used for bioaugmentation. Two GROs were conducted for 60 days: 1) vermiremediation by Eisenia foetida without/with biostimulation with compost from organic waste; 2) bioaugmentation of a Proteobacteria and Firmicutes consortium under anaerobic and/or aerobic conditions, and biostimulation with the compost. Finally, the removals determined the efficiency of each treatment. In the first GRO, all the earthworms died by intoxication after 48 h of experimentation. In the second GRO, the highest removals were obtained with the anaerobic treatment: 27% 4,4'-DDT, 52% 4,4'-DDE, 58% 4,4'-DDD, 72% α-HCH, 35% β-HCH, 92% γ-HCH, and 23% δ-HCH. The results indicate that vermiremediation is not feasible for restoring soils with these pollutants at the studied levels. On the contrary, although the synergy between bioaugmentation and biostimulation represents a promising alternative, it is crucial to conduct longer evaluations of the proposed treatments to better understand their effects on the decontamination of soils with DDT and HCH.