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E3 Journal of Environmental Research and Management

E3 Journal of Environmental Research and Management Vol. 3 (5) pp. 099-0107, June 2012; © E3 Journals; ISSN 2141-7466


Quantitative structure-activity relationship biodegradability modeling in biofiltration of petroleum volatile organic compounds

M. N. Ondiaka1,2 * , J. M. Mutua1 , A. N. Gitau1 * , B.N.K Njoroge3
1 School of Engineering, Department of Environmental and Biosystems Engineering, University of Nairobi, P.O. Box 30197-00100, Nairobi
2 Applied Bioprospecting Programme, International Center of Insect Physiology and Ecology (ICIPE), P.O. Box 30772-00100, Nairobi, Kenya
3 Department of Civil and Construction Engineering, University of Nairobi, P.O. Box 30197 Nairobi, Kenya. Accepted 10 April, 2012
*Corresponding Author E-mail: gitauan@yahoo.co.uk
Accepted 10 April 2012

Abstract

A quantitative structure activity-relationship (QSAR) biodegradability model was developed to predict removal capacity of volatile organic compounds (VOCs) in a compost biofilter. Experimental data for o-Xylene, 1,3,5-Trimethylbenzene and 1,2,4-Trimethylbenzene was used to develop the model. Biodegradability rate was correlated with three molecular and five quantum mechanical derived descriptor variables. Regression results showed very strong significance between biodegradability of compounds and their molecular weight, Mw (r2 = 0.995), log octanol-water partition coefficient, pKow (r2 =0.880), highest occupied molecular orbital energy, Ehomo (r2 = 0.989), lowest unoccupied molecular orbital energy, Elumo (r2 = 1.000) and energy gap, E (r2 = 0.987). Model significance with excited state energy, Ees (r2 = 0.678) and ground state dipole moments, (r2 = 0.649) was strong. Log Henry’s Constant, H, had weak significance of r2 = 0.461. The descriptors were screened and a complete biodegradability model developed using molecular weight and logarithm octanol-water partition coefficient. The model was calibrated using toluene, ethylbenzene, benzenepropyl-, decane and undecane VOCs and tested. Results showed high prediction of xylene and trimethylbenzene isomers, toluene, ethylbenzene, benzenepropyl-, decane and undecane biodegradability in the biofilter.

Keywords: Modeling; biodegradability; biofiltration; VOCs; significant descriptors.

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