BIODEGRADATION KINETICS OF CARBON-TETRACHLORIDE BY PSEUDOMONAS-CEPACIA UNDER VARYING OXIDATION-REDUCTION POTENTIAL CONDITIONS

In recent years, considerable interest has been given to the in situ d egradation of hazardous contaminants by stimulating indigenous microor ganisms. Optimization of environmental conditions, especially oxidatio n-reduction potential (ORP), for metabolism of hazardous constituents by indigenous microorganisms may assist in cost- effective mitigation by enhanced bioremediation. Pseudomonas cepacia, the predominant speci es, was selected as the microorganism of study to evaluate ORP effects on biodegradation of carbon tetrachloride (CT), a common contaminant in many sites. Titanium (III) citrate was used to poise ORP at desired levels. Results indicate that initial ORP appears to be critical for initiating the CT degradation process. Substantial CT degradation occu rred when cultures were poised at negative ORP conditions, while negli gible CT removal was observed at oxidative ORP conditions. Accumulatio n of chloroform (CF) produced by CT metabolism was not observed, which may be attributed to its metabolism by P. cepacia and another pathway that preclude CF generation. The maximum biodegradation rate was foun d to occur at approximately -150 mv(2) and an overall substrate remova l rate constant, K, of 6.9 x 10(-3) h(-1) was observed al an initial C T concentration of 323 mu g/L.