| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 94 === Progress in thin film transistor liquid crystal display (TFT-LCD) manufacturing industry is promising in Taiwan. Nowadays the mass production of TFT-LCD in Taiwan is in the second place of the world, following Korea. The Taiwanese production value will reach one trillion NT dollars in the near future. However, the LCD manufacturing wastewater will also increase to approximately 200000 m3/day. Characterization analysis of TFT-LCD manufacturing wastewater discharged from two plants was conducted. It is found that the ratio of organic nitrogen to organic carbon in the wastewater is relatively high(>0.05). The main components of the wastewater comprise stripper (DMSO&MEA), developer (TMAH) and chelating agents.
In this study, the performance and the ecology of microorganisms in aerobic Non-woven Membrane Bioreactor (N-MBR) is discussed. Six runs with different loading are conducted, including synthetic substrate and in-site TFT-LCD manufacturing wastewater. Aerobic N-MBR achieved good removal efficiency for DMSO、MEA and TMAH. From Run I to Run IV, 80 % ~ 90 % of COD, TOC and 75 % ~ 95 % of Org-N are removed by aerobic N-MBR. At the beginning of Run V, MEA degrading bacteria is affect by the addition of in-site TFT-LCD manufacturing wasterwater. The removel percentage of MEA and Org-N is 66% and 34% respectively. At the end of Run V, both removel rate return to 90%. During Run VI, the treatment of the specific components is well performed. N-MBR can treat TFT-LCD manufacturing wastewater effectively.
According to the observation of scanning electron microscope (SEM), coccus and bacillus are the main population in N-MBR through the whole operational period. Molecular biotechnology is also used for clarifying the ecology of TFT-LCD manufacturing wastewater degrading microorganism. Cloning library was conducted for the suspended sludge taken at day 461. Base on cloning-sequence anaysis from 84 clones, the population percentage of DMSO-degrading microorganism Hyphomicrobium denitrificans and Rhodobacter sp. were 31%, and 6%. In addition, TMAH-degrading microorganism Paracoccus sp. and Methyloversatilis universalis were 12 %, and 6 %, respectively.
Terminal restriction fragment length polymorphism (T-RFLP) was modified and developed for the identification of nitrifying bacteria in TFT-LCD wastewater treatment system. Aerobic N-MBR fingerprint of bacterial species could be expressed from the T.RFLP diagram. Several species of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were identified based on the genetic database. According to T-RFLP results, Nitrosomonas europaea was the dominant AOB in N-MBR after day 190. At day 413, Nitrosomonas commuins or N. marina became the dominant AOB in N-MBR. After the removal rate of MEA is affected by in-site wastewater (day 531), the domaint AOB shifted to Nitrosospira genus. For NOB, Nitrobacter and Nitrospira existed in the whole operational period.
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