This study explores the use of carbon-based materials, specifically biochar and hydrochar, to enhance toluene removal in microaerobic conditions with nitrate addition in extracted groundwater. Biochar and hydrochar exhibit adsorption capabilities for toluene, with biochar maintaining stable toluene removal efficiency by reducing NO3−-N loss through partial denitrification. Additionally, biochar stimulates the growth of toluene-degrading bacteria, including Thauera, Rhodococcus, Ideonella, and Denitratisoma, capable of denitrification. In contrast, hydrochar stimulates denitrifiers without toluene-degrading capacity, such as Candidatus Competibacter and Ferrovibrio. The study emphasizes the importance of low NO3−-N concentrations in reducing toluene-degrading capacity.

Groundwater pollution from petroleum leakage poses a significant environmental challenge, and multi-phase extraction (MPE) emerges as an effective treatment technology. Biotreatment utilizing microorganisms is a cost-effective method for organic contaminant degradation in extracted groundwater, where nitrate serves as a suitable electron acceptor. The study suggests that the mixed electron acceptors of oxygen and nitrate can benefit biodegradation processes by stimulating both aerobic and anaerobic enzymatic pathways.

The research contributes to understanding the dynamic interactions in groundwater remediation using biochar and hydrochar, providing insights into microbial community structures, toluene-degrading bacteria, and denitrifiers. Ultimately, these findings offer valuable information for developing remediation techniques for contaminated groundwater.