| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 96 === Polycyclic aromatic hydrocarbons (PAHs) are one of the most important contaminants released in the environment. Anaerobic degradation of PAHs has been demonstrated in several microcosm studies. In this study, anaerobic fluorene degradation by sulfate reducing bacterial enrichment culture was investigated. Subsequently, batch biodegradation experiments were designed using the central composite design (CCD) and carried out to estimate the optimum operating conditions of sulfate reducing bacteria (SRB) and sulfate concentrations. Biodegradation rates of fluorene were 0.21 mg/L-d in zero-order and 0.1/d in first-order kinetics.
Response surface methodology (RSM) was used to optimize the sulfate and biomass concentrations, and was used to develop a model for the responses. Applying the desirability function, the optimum conditions of sulfate and biomass concentrations were found as 14.4 mM and 37.8 mg/L, respectively. The highest fluorene removal percentage of 90% was observed at optimum conditions.
In addition, the inhibition kinetics of fluorene biodegradation by SRB were investigated over a range of initial fluorene concentrations (from 0 to 100 mg/L) using the Haldane’s model. The kinetics parameters obtained were �慆ax of 0.35/d, Ks of 0.07 mg/L and Ki of 600 mg/L. Due to the addition of solvents (dichloromethane, N,N-dimethylformamide) and yeast extract in the PAHs biodegradation experiments, microorganisms grew using DMF and/or yeast extract which result no toxicity in the inhibition study. However, the fluorene biodegradation by SRB can be inhibited when fluorene concentration is higher than 600 mg/L. The FISH analysis showed that SRB was the major species in the enriched bacterial culture.
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