MONITORING THE BIOLOGICAL TREATMENT OF ANTHRACENE-CONTAMINATED SOIL IN A ROTATING-DRUM BIOREACTOR

A 2-kg-capacity rotating-drum reactor was used for biological conversi on of nearly insoluble organic contaminants in soil. The rotating moti on allowed effective operation at a solids content of over 60% by weig ht. 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 o peration, in which fresh soil was inoculated with 20% spent slurry fro m the previous run. Maximum degradation rates of 100-150mg anthracene (kg soil)(-1) day(-1) were achieved throughout the experiments. Evolut ion 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 ant hracene as sole carbon source to a mixture of three polynuclear aromat ic hydrocarbons, the culture was able to degrade each of these in the sequence: anthracene, phenanthrene and finally pyrene.