Application of EDTA-degrading bacterium to Metal-EDTA on Wastewater Treatment

• Main Authors: Zhi-Cheng Chang, 張志誠
• Other Authors: Hung-Yuan Fang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/81355112020777017583

碩士 === 國立雲林科技大學 === 環境與安全工程系碩士班 === 92 === EDTA (ethylenediaminetetraacetic acid), the target compound of this study from the effluent of secondary biotreatment units and waste liquid, can be biodegraded by special microorganisms. We also have successfully isolated a bacterial strain that can degrade EDTA in our laboratory. This bacterium was identified Burkhol epacia YL-6. So this study focuses YL-6 applied to EDTA wastewater treatment, significantly promoted EDTA by using the YL-6 bioaugmentation agent to accumulation the activated sludge. So we try to apply the bacterium to the Cu-EDTA and wastewater in a PC board plant. Hope can solve higher COD problem in the system from EDTA. The experiment of EDTA degradation was performed on a shake flask with the addition of YL-6 bioaugmentation agent. The results showed that the degradation efficiency of Fe-EDTA and Cu-EDTA were 94.8% and 91.5%. The blank with light source can be degraded by light but very slowly, and the degradation efficiency of Fe-EDTA was higher than Cu-EDTA. The degradation test of Fe-EDTA and Cu-EDTA by addition the compound E as the bioaugmentation agent showed that the degradation efficiency were 98.58% and 97.88%, respectively. The degradation efficiency and biomass were significantly promoted by using the compound E as the bioaugmentation agent. The activated sludge and raw wastewater were taken from PC Board wastewater treatment plant. It was cultivated in batch pilot to simulate the degradation of metal-EDTA by the strain of YL-6. The activated sludge from PC Board plant was divided into two sets-experimental set with and contradistinctive set, without YL-6 bioaugmentation agent. In the experimental system of pilot plant, 2 L activated sludge was mixed with 2 L raw wastewater. In order to avoid the death of microorganism which cause by the raw wastewater, the raw wastewater will be pretreated by chemical coagulation to remove the heavy metals. The raw wastewater will be diluted (ratio 20:1) firstly for the adaptation of activated sludge. Then the dilution ration will be 10, 5, 1 and finally the raw wastewater for the accumulation of the activated sludge. At the primary stage of accumulation for the dilution ration (20:1), the growth of the microorganism was inhibited until the 8th days, then the activated sludge reached the steady state. After 2 days, Fe-EDTA can be degraded completely and the residual of Cu-EDTA was 3 mg/L. After 25 days, the residual of COD was 97 mg/L and the removal efficiency was 92.9%. For the contradistinctive set, the removal efficiency of COD was 25.2% and TOC was 90.57%. Similarly, for the dilution ration 10, 5, 1 and raw wastewater, at the beginning of accumulation, the growth was inhibited and increased, the removal efficiency of EDTA, COD and TOC were lower. From the results of the experiment, the step by step accumulation can be used to adapt the bioaugmentation agents YL-6 to the activated sludge system, it can enhance the degradation of Fe-EDTA and Cu-EDTA, but it can’t achieve the effluent standard of COD in shorter time.