Experimental Study of Biodegradation of Ethanol and Toluene Vapors

ethanol. These results clearly indicate the volatile, hydrophobic nature of toluene,
relative to that of ethanol.
In this study, it was found that unless ethanol or benzyl alcohol was added to the
reaction mixture, Pseudomonas putida could not oxidize toluene continuously. This
agrees with the results of Gibson et al. (1968). They discovered that the crude cell
extracts of Pseudomonas putida that grow on benzyl alcohol contained an active
dehydrogenase which permits benzyl alcohol to produce NADH 2 . This reduced NAD is
required in the initial reaction of toluene.
Appreciable bioremediation rates of both ethanol and toluene from
contaminated air streams using a traditional, well-mixed bioreactor were achieved. By
operating the bioreactor in a continuous mode, ethanol removal efficiencies reached
100% with inlet loadings up to 304 mg/L-h. Using ethanol as co-substrate, the removal
efficiency reached 100% for ethanol and 89% for toluene at ethanol inlet concentration
of 15.9 mg/L and toluene inlet concentration of 4.5 mg/L. With the presence of benzyl
alcohol as co-substrate at inlet toluene concentrations and total loadings up to 5.7 mg/L
and 171 mg/L-h, toluene removal efficiencies were as high as 97 %. A summary of the
bioremediation results for ethanol and toluene removal in this study is provided in Table
4-3. These results compare favorably to biofiltration units for the removal of either
ethanol or toluene from contaminated air streams, and bode well for commercial
implementation since well-mixed bioreactors are much easier to operate than biofilters.
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