A full scale batch process has been implemented as the DMT-Biodyn process (Sinder et al., 1999). The process consists of a fluidized-bed slurry reactor in which fined-grained contaminated soils are treated. For aeration, the slurry circulation loop is treated in an external bubble column (Fig. 11.9). The reactor configuration allows a high solids loading, up to 50 wt%. The DMT-Biodyn process was designed by the Deutsche Montan Technologie GmbH to treat PAH-polluted sites at former coal facilities in the Federal Republic of Germany (Nitschke, 1994).
On a pilot scale (a 1.2 m3 reactor) various technological parameters were investigated and the hydraulic feed system at the bottom was optimized. Experiments showed that PAH degraded rapidly without a noticeable lag phase; the measured oxygen consumption rate correlated with the PAH degradation rate. For this specific soil (starting concentration of PAH about 250 mg kg-1), the target levels were reached after 6 d. Comparison of the pilot results with results on a laboratory scale using a respirometer showed that the degradation of this test soil in each of these systems was similar. With a higher level of PAH contamination (starting at 1100 mg kg-1), the target levels could not be reached (treatment time, 30 d). The researchers concluded that, for this specific soil, "adsorption of the PAH to the organic matrix results in a reduced bioavailability". Later experiments on this contaminated soil, in contaminated soil
Was this article helpful?