Recovery of trichloroethylene removal efficiency through short-term toluene feeding in a biofilter enriched withPseudomonas putida F1

Abstract

Trichloroethylene (TCE) is an environmental contaminant provoking genetic mutation and damages to liver and central nerve system even at low concentrations. A practical scheme is reported using toluene as a primary substrate to revitalize the biofilter column for an extended period of TCE degradation. The rate of trichloroethylene (TCE) degradation byPseudomonas putida F1 at 25°C decreased exponentially with time, without toluene feeding to a biofilter column (11 cm I.D.×95 cm height). The rate of decrease was 2.5 times faster at a TCE concentration of 970 μg/L compared to a TCE concentration of 110 μg/L. The TCE itself was not toxic to the cells, but the metabolic intermediates of the TCE degradation were apparently responsible for the decrease in the TCE degradation rate. A short-term (2 h) supply of toluene (2,200 μg/L) at an empty bed residence time (EBRT) of 6.4 min recovered the relative column activity by 43% when the TCE removal efficiency at the time of toluene feeding was 58%. The recovery of the TCE removal efficiency increased at higher incoming toluene concentrations and longer toluene supply durations according to the Monod type of kinetic expression. A longer duration (1.4∼2.4 times) of toluene supply increased the recovery of the TCE removal efficieny by 20% for the same toluene load.