A Microcosm Study on P-nitrophenol Biodegradation in Slurry Phase by Alcaligenes faecalise and Screening of Effective Factors

فاقد چكيده

Bioremediation of soils contaminated with nitroaromatic hydrocarbons has recently attracted the attention of researchers due to their toxic effects among which p-nitrophenol (PNP) can be discharged into soil matrices during production, distribution, and application of pesticides, insecticides and drugs. The purpose of this study is to examine PNP biodegradation in a microcosm consisting of kaolan clay soil in order to decrease its pollution by A. faecalise, the superior bacterium among the four bacterial species tested. To detect the effective factors on PNP biodegradation, Plackett-Burman design method was employed using eight factors consisting of PNP concentration (30, 70mgkg-1), temperature (20, 35°C), soil-water ratio (20, 40%(v/w)), initial pH (7, 9), inoculume size (5, 10%), yeast concentaraion (0.1, 1gl-1), glucose (0.5, 1.5gl-1) and preexposure to PNP (10, 30mgkg-1). PNP reductions of 20.9% up to 75.5% were obtained in soil slurries using A. faecalise under the conditions used after 12 days. Analyses of variance revealed that 5 out of 8 factors had significant effect on PNP biodegradation. By using 4 center points, it was also found that significant curvature exists in the design space and hence non-linear design methods should be used to find out the optimal conditions for PNP removal in slurry phase.