Biochar-microbe-hydrogel with cyclic hydraulic leaching establishing niches for integrated soil-groundwater...

Bioremediation of soil and groundwater contaminated by persistent organic pollutants (e.g., chlorinated organics) using functional bacteria faces inherent challenges, such as competition from indigenous microorganisms (exogenous bacteria is difficult to establish microbial niches in soil) and poor pollutant accessibility. This study developed an integrated strategy that combines Biochar-Microbe-Hydrogel (BMH) matrix with Cyclic Hydraulic Leaching (CHL) for the concurrent bioremediation of soil-groundwater. The BMH is active gel beads encapsulated functional bacteria in porous biochar with hydrogel. The lab-scale soil column experiments demonstrated a 91.4 % removal efficiency for 2,4,6-trichloropherol (TCP) from a high contaminated soil concentration of 667 mg·kg^-1, substantially outperforming the controls (53.9 %). The water flow by cyclic leaching promoted the elution of TCP from soil, followed by its re-adsorption and subsequent biodegradation in the BMH matrix. The constant proliferated bacteria (in this study we used Sphingomonas fennica as TCP degrading bacteria) migrated through biochar channels, constructing its niches along soil profile. This study also observed that the bacteria S. fennica competed with native soil microorganisms for niches in its high-density existence, but a shift toward cooperation was found at its low microbial abundance. This study provides an integrated bioremediation solution of soil and groundwater (BMHCHL) that is highly prospective for achieving effective field application.