Biodegradation of naphthalene-contaminated soils in slurry bioreactors

The effects of naphthalene concentrations and soil constituents (sand, clay , organic matter) on biodegrading naphthalene-contaminated soils using an a cclimated Flavobacterium sp. were examined in continuously stirred slurry b ioreactors. Soils with and without organic matter (1%) and kaolinite clay ( 20%) were used. Studies showed that sorption of naphthalene can be represen ted by the Freundlich isotherm. Among the soils investigated, clayey soil r etarded the biodegradation process the most due to its desorption character istics. Increasing the naphthalene contamination level from 500 mg/kg to 25 ,000 mg/kg doubled the biodegradation time in the slurry reactor with a soi l loading of 10 gn. A pseudo first-order kinetic was observed for naphthale ne biodegradation, and the biodegradation constant was determined to be 0.2 0 mg/L/h. A kinetic model was developed to simulate the biodegradation of n aphthalene in a continuously stirred batch slurry reactor and to understand the role of solubilization (solid phase naphthalene), desorption, and biod egradation in the removal of naphthalene. Predictions using the numerical m odel agreed with the experimental data.