Table 1.
Mechanisms associated with the initial step in the biodegradation of each type of VOC.
| Category | Compounds | Aerobic degradation | Anaerobic degradation |
|---|---|---|---|
| Chlorinated ethenes | Tetrachloroethene (PCE) | Oxidation*1 | Reductive dechlorination116,164) |
| Trichloroethene (TCE) | Oxidation115,201) | ||
| Dichloroethene (DCE) cis-dichloroethene (cis-DCE) trans-dichloroethene (trans-DCE) 1,1-dichloroethene (1,1-DCE) | |||
| Vinyl chloride (VC) | |||
| BTEX | Benzene | Oxidation57,58,186) | *2 |
| Toluene | Fumarate addition199) | ||
| Ethylbenzene | Oxidation/fumarate addition16,199) | ||
| Xylene o-xylene m-xylene p-xylene |
Fumarate addition96,199) | ||
| Chlorinated methanes | Carbon tetrachloride (CT) | *3 | Reductive dechlorination61,146) |
| Chloroform (CF) | Oxidation28) | ||
| Dichloromethane (DCM) | Dechlorination (glutathione substitution)127) | Fermentation105) |
*1
The aerobic degradation of PCE is limited, except as described by Ryoo et al. (155).
*2
The mechanisms underlying the anaerobic degradation of benzene are unclear, although hydroxylation to phenol, methylation to toluene, and carboxylation to benzoate were proposed by Weelink et al. (199).
*3
The aerobic degradation of CT remains ambiguous.