Enhanced bioremediation of BTEX contaminated groundwater in pot-scale wetlands

Pot-scale wetlands were used to investigate the role of plants in enhancing the performance of engineered bioremediation techniques like biostimulation, bioaugmentation, and phytoremediation collectively. Canna generalis plants were grown hydroponically in BTEX contaminated groundwater supplied in wetland mesocosms. To quantify the contaminant uptake by the plants, wetlands with and without shoot biomass along with unplanted gravel bed were used under controlled conditions. The residual concentration of the selected BTEX compound, toluene, in the rhizosphere water was measured over the entire period of the experiment along with the water lost by evapotranspiration. The rate of biodegradation in all wetland mesocosms fitted best with the first-order kinetics. The total removal time of the BTEX compound was found to be highest in the unplanted gravel bed mesocosm followed by wetlands without and with shoot biomass. The cumulative uptake of toluene in shoot biomass of the wetland plants initially increased rapidly and started to decrease subsequently till it reached a peak value. Continuity equations integrated with biodegradation and plant uptake sink terms were developed to simulate residual concentration of toluene in rhizospheric water for comparison with the measured data for entire period of the experiments. The results of this research can be used to frame in situ plant-assisted bioremediation techniques for hydrocarbon-contaminated soil-water resources.