Biological remediation of anthracene-contaminated soil in rotating bioreactors

Soil impregnated with anthracene was subjected to bacterial treatment as a model for remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs). Roller bottles were used to simulate the mixing of solids in rotating drums. The soil was prepared as a 60 weight % slurry in salts medium, and inoculated with a mixed culture, selected for the ability to mineralize anthracene as its sole carbon source. The degradation of anthracene followed zero-order kinetics when it was well dispersed on the soil particles, consistent with a rate limitation by dissolution of solid hydrocarbon. Maximum degradation rates of 300 g/g per day were achieved in repeated batch operation, using a 10% volume of soil slurry as the inoculum for the succeeding batch. Anthracene degradation activity was maintained through 18 such transfers on a 3- to 4-day cycle. The culture produced soluble compounds that enhanced the solubility of anthracene in aqueous solution. Soil components did not have a significant effect on growth or degradation. Degradation of anthracene ceased when the concentration in soil dropped to approx. 30 g/g, from an initial value of 600 g/g. Correspondence to: M. R. Gray