| Summary: | 碩士 === 國立中興大學 === 環境工程學系 === 89 === The upflow anaerobic sludge bed (UASB) process was superior to be operated under coupled anaerobic/aerobic conditions via its granular sludge. It seems a good idea to complete the sequential degradation of tetrachloroethylene (PCE) with this coupled anaerobic/aerobic condition. The main objective of this study was to discuss the effect of external addition of oxygen on the biodegradability of PCE and the formed intermediates under a simultaneous anaerobic/aerobic system. The effects of different concentrations and addition modes of substrate (sodium acetate) on the biodegradability of PCE under an anaerobic system were studied. And, the acclimation effect on the two systems was also explored.
The experimental results of external oxygen additions indicated that under the oxygen content of 5.2 to 10.4 % in the headspace of the reaction bottles, the anaerobic/aerobic coupled system performed a higher degradation efficiency for chlorinated ethenes. The results showed that an increase in the concentrations of acetate from 50 to 500mg/L increased the total PCE dechlorination rates from 4.29 to 8.15 nmol PCE/g-VS-d under the batch mode of substrate addition. Furthermore, increasing the concentrations of acetate from 100 to 500 mg/L under the semi-continuous addition mode increased the final removal rate from 35 to 52 %. The results also showed that the minimum total removal rate under a semi-continuous mode was similar to the maximum total removal rate under a batch mode. Therefore, the semi-continuous acetate addition was better than the batch mode. And, the result showed no significant effect on the biodegradability of PCE for the anaerobic system. However, after being acclimated, the PCE removal rate in the simultaneous anaerobic/aerobic system was higher than the absolute anaerobic system, which could be due to the improved toxic resistance of the granular sludge through the acclimation. Thus, if PCE would be treated by a coupled anaerobic/aerobic system, it was suggested that the acclimated granular sludge should be used for well-dechlorination of PCE.
|
|---|
