Enhanced in situ bioremediation of phenol in bioestimulated unsaturated and saturated sand-bed columns

Biodegradation of phenol was observed in unsaturated sand-bed columns, in which phenol concentration declined from 298 mg phenol/kg sand to less than 1 mg/kg after 21 days. In saturated sand-bed columns, phenol concentration declined from 230 mg phenol/kg to less than 1 mg/kg after 37 days. Pseudo-first-order phenol biodegradation rates were in the range 0.25 days(-1) (R(2) = 0.9) to 0.66 days(-1) (R(2) = 0.85) and 0.08 days(-1) (R(2) = 0.68) to 0.14 days(-1) (R(2) = 0.84) in the unsaturated and saturated sand-bed columns, respectively. Unsaturated columns presented a higher biomass density (21.5 mg/g) in the sand-bed and lower biomass concentration in the aqueous phase (3.5 NTU) compared with the saturated columns (6.4 mg/g and 14.0 NTU). A high concentration of phenol releases in the sand-bed columns resulted in an initial inhibition of microbial activity and destabilization of the attached biomass.