Modeling the biodegradation kinetics of aromatic and aliphatic volatile pollutant mixture in liquid phase

• Biodegradation of complex mixtures of VOCs was evaluated.
• Different combination of MEK, MIBK, toluene, o-xylene and ethyl benzene were used.
• A general mixed-substrate biodegradation model was developed.
• Model incorporates self inhibition and various interactions between compounds.
• Model predicted biodegradation of mixtures of similar/dissimilar VOCs was satisfactory.

Volatile Organic Carbon (VOC) emissions from industries typically consist of a mixture of compounds of different chemical properties. The biodegradation kinetics of individual VOCs often get affected in the presence of other VOC species. In the present study, biodegradation kinetics of different multiple substrate mixtures of common industrial ketones viz. methyl ethyl ketone (M) and methyl iso-butyl ketone (B); and mono-aromatic VOCs such as toluene (T), ethyl benzene (EB) and o-xylene (X) were studied. Acclimatized aerobic bacterial consortium was used for the biodegradation study. A general mixed-substrate biodegradation model was developed which can describe the biodegradation kinetics of common industrial VOCs when present as a mixture, incorporating biokinetic parameters obtained from single substrate biodegradation studies. This model also employs a parameter for interaction effect, which may be obtained from biodegradation studies with binary mixtures. Three types of basic inhibitions, possible in the biodegradation of any mixture i.e. (i) self-substrate inhibition, (ii) interactive inhibition among VOCs of similar chemical nature and (iii) inhibition due to dissimilar VOC species, are considered in the general model. The performance of the proposed model was evaluated using the experimental data obtained from a previously published work, as well as from relevant data reported in the literature. High E-values obtained consistently for the simulations indicated good performance of the proposed model. This general model can be used for simulating the biodegradation of mixtures of similar/dissimilar VOCs and may be helpful in the optimal design of biological systems treating multiple VOCs.