| Summary: | 博士 === 大葉大學 === 環境工程學系碩士班 === 103 === Xenobiotic organic chemicals are foreign to natural microbial. Indigenous microorganisms can degrade a persistent xenobiotic compound after going through an acclimation process, and in these processes, a large amount of energy for metabolism is spent. Thus, energy storage of cells may become deficit. Shortening lag phase and enhancement xenobiotics degradation rate were two main aims deciding the successful biological treatment of xenobiotics. The prolonged acclimation phase and slow degradation rate of a xenobiotic were due to low cell yield and insufficient energy contained in the cells.
This study was to investigate possible ways to enhance the degradation rate of activated sludge for a sample xenobiotic. Main factor of concentration for this rate study is the energy aspect of activated sludge in relationship with the sludge’s efficiency in degradation of a xenobiotic.
In the tests aimed to shortening lag phase and enhancement degradation rate, biogenic substrates were supplemented and energy contents (ATP) of activated sludge cells were measured. Tests with both acclimation and degradation phases were conducted with the supplements of biogenic substrates, typically with sucrose and peptone.
Using 2,4-D as the sample xenobiotic, acclimation test results showed that lag time in tests with sucrose re-cultivated activated sludge had shorten by 1 day compared with original activated sludge. In tests with acclimated activated sludge, biogenic substrates may enhance or slow-down xenobiotic degradation rate, pointing to an optimal supplement of biogenic substrate. Conditions for advantageous biogenic supplementation were identified for activated sludge degradation of a xenobiotic; specifically, highest degradation rate enhancements occurred when biomass yielded by biogenic substrates was approximately double that yielded by 2,4-D.
Energy aspect of activated sludge acclimation and degradation of 2,4-D was measured as ATP contents of the working sludge. ATP measurement results show that ATP per unit mass of sludge biomass was lowered after sludge had degraded 2,4-D. Amount of sludge grown was inevitably lowered due to an energy deficit after 2,4-D catabolism. Biogenic addition indeed increased the average ATP content. Enriched ATP from supplemented biogenic substrates was able to sustain the energy deficit. Thus, ATP enrichment by supplemented biogenic was an efficiency method in xenobiotic treatment bioprocess.
This study also developed an ATP measurement was simple, rapid, reliable, and was unburdened of some limitations other methods may have. Cells disruption and HPLC measurement of ATP was evaluated for its linearity, limits of detection, and reproducibility. Evaluation test results reported a R2 of 0.999 of linear fit of ATP concentration versus activated sludge concentration, a LOD = 0.00045 mg/L, a LOQ = 0.0015 mg/L for HPLC measurement of ATP, a MDL = 0.46 µg/g SS for ATP extraction protocol, and a recovery efficiency of 96.4 ± 2 percentage.
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