Monitoring the biological treatment of anthracene-contaminated soil in a rotating-drum bioreactor

A 2-kg-capacity rotating-drum reactor was used for biological conversion of nearly insoluble organic contaminants in soil. The rotating motion allowed effective operation at a solids content of over 60% by weight. A mixed bacterial culture was used to degrade anthracene that had been impregnated into a representative high-clay soil. The activity of the culture was sustained over a period of months in repeated batch operation, in which fresh soil was inoculated with 20% spent slurry from the previous run. Maximum degradation rates of 100–150 mg anthracene (kg soil)^–1 day^–1 were achieved throughout the experiments. Evolution of carbon dioxide from the bioreactor showed that degradation and mineralization of anthracene occurred simultaneously, and that 55% of the anthracene was mineralized. When the culture was switched from anthracene as sole carbon source to a mixture of three polynuclear aromatic hydrocarbons, the culture was able to degrade each of these in the sequence: anthracene, phenanthrene and finally pyrene.