| Summary: | 碩士 === 國立中興大學 === 環境工程學系 === 88 === ABSTRACT
The objective of this study is to discuss whether the direct addition of hydrogen could enhance the reductive dechlorination of PCE. The effects of the concentrations of biomass and AcNa in reductive dechlorination of PCE were also studied.
The experimental results showed that PCE was no apparent to degrade by direct hydrogen addition without the presence of substrate (AcNa = 0 mg/L). However PCE was apparent by degraded in reactor contain both hydrogen and substrate ( AcNa = 600 mg/L). When the concentration of hydrogen increased from 0 ppm to 60 ppm in the presence of AcNa, the initial PCE removal rate increased from 1.73 nmol/day to 3.34 nmol/day. But the concentration of hydrogen increased from 60 ppm to 500 ppm, the initial PCE removal rate decreased from 3.34 nmol/day to 2.25 nmol/day. The major pathway for hydrogen in the reactor was to form CH4, but not to be used for reductive dechlorination.
The results of biomass study showed that the concentration of biomass increased from 3.5 mg-MLVSS/L to 350 mg-MLVSS/bottle, the initial first order reaction rate constant for PCE removal increased from 0.017 day-1 to 0.046 day-1, the initial PCE removal rate increased from 1.03 nmol/day to 3.4 nmol/day. On the other hand, with the same amount of substrate added, the total amount of degraded PCE decreased from 74.9 nmol/bottle to 23.26 nmol/bottle when the biomass conc. increased from 3.5 mg-MLVSS/L to 350 mg-MLVSS/bottle respectively. The ratio of total amount of PCE degraded to the total of AcNa consumed decreased form 0.0272 nmol/bottle to 0.0031 nmol/bottle. Although higher biomass had high initial PCE removal rate, but the total amount of PCE removal rate decreased.
The results of the effect of AcNa conc. study showed that an in increase in AcNa concentrations increased the initial PCE removal rate, but when concentration of AcNa reached to 500 mg/L, the initial removal rate PCE decreased. When the concentrations of AcNa increased from 0 mg/L to 500 mg/L, the total amount of PCE removed increased from 7.55 nmol/bottle to 32.17 nmol/bottle.
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