In situ TCE bioremediation study using electrokinetic cometabolite injection

The feasibility was evaluated of using electrokinetic injection of benzoic acid cometabolite to enhance the biodegradation of a representative recalci trant contaminant, trichloroethene (TCE). Whereas in flask studies, sulfate ion alone enhanced TCE (at 6 ppm) degradation rates over those found in th e absence of suitable additives, benzoic acid showed enhanced degradation r ates for TCE at 6-50 ppm levels. Following injection of benzoic acid cometa bolite into a 1 m column of TCE contaminated Loess clay, the TCE first orde r degradation rate at the periphery was determined to be (0.039 +/- 0.007) day(-1), a value in good agreement with an anaerobic slurry flask tests at 30 degrees C, (0.047 +/- 0.009) day(-1). However, unless the rate of inject ion of an additive is made compatible with its rate of consumption, these c olumn results and a theoretical model reveal that homogeneous penetration o f additive is not achieved. It is cautioned that knowledge of the rate of d egradation of a carbon source enhancer (or additive) is critical for engine ering its homogeneous injection, whether by hydraulic or electrokinetic met hods. These results demonstrate that electrokinetic degradation of recalcit rant wastes may be practical, in particular for those sites whose soil medi a have low coefficients of hydraulic permeability (clay deposits, silty cla ys, etc.) where traditional pump and treat technology is ineffective. (C) 2 000 Elsevier Science Ltd. All rights reserved.