Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/5150
標題: 廠用冷卻水中鐵氧化菌腐蝕特性與生物膜族群分析之研究
The corrosion process characteristics of Fe-oxidizing bacteria and microbial diversity in biofilms from the cooling water system
作者: 陳雅純
Chen, Ya-Chun
關鍵字: microbiologically influenced corrosion;微生物 腐蝕
出版社: 環境工程學系所
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摘要: 
本研究目的為分析某電廠廠用冷卻水系統中之生物膜族群隨著時間增長之變異,藉此推測其與系統腐蝕現象之相關性;並且探討高溫純種菌株TPH-7腐蝕程序特性與不同階段的電化學變化,試驗腐蝕抑制劑與殺菌劑較佳添加量,以期能降低微生物造成的腐蝕現象。
由實場生物膜族群DGGE分析可知,生物膜中存在之菌群很可能造成此冷卻水系統微生物腐蝕(MIC)現象,因為生物膜中有具鐵氧化能力、表面附著能力或與腐蝕相關之菌株存在。
腐蝕抑制劑鉬酸鈉在實驗溶液中添加濃度愈大則腐蝕電流愈小,達100 ppm時,鉬酸鹽可於A106碳鋼表面形成緻密氧化膜以達保護效果,實驗20天後之腐蝕電流降低至7μA;但是,若有菌株TPH-7存在,則會破壞鉬酸鹽之防蝕機制,實驗20天後之腐蝕電流仍高(42μA),重量損失也比無菌條件下大的多。
於2個月監測期間,商用殺菌劑A與ClO2添加濃度個別在50 ppm與100 ppm以上對於菌株TPH-7(懸浮態)有很好的殺菌效果;然而,對於附著於碳鋼表面之菌體無效,因為此二種殺菌劑個別添加100 ppm時,腐蝕電流沒有因殺菌劑之作用而顯著降低,20天後之腐蝕電流皆約45μA左右。
額外添加高EPS菌株TPH-13-3時,碳鋼試片之腐蝕電流沒有大幅度增加,推測菌株TPH-13-3不會明顯促進菌株TPH-7對碳鋼之腐蝕程度。
綜合上述研究結果,若要改善廠用冷卻水系統之腐蝕問題則需抑制生物膜之生成。另一方面,菌株TPH-7會與鉬酸鹽競爭吸附位置而破壞其防蝕機制,若要達到防蝕效果,則鉬酸鈉之添加濃度需再提高,所需添加量必須再經實驗測試;殺菌劑對附著於基材表面之菌體效果不良,若要運用於實場系統中,則需進一步測試殺菌劑對附著在表面之菌體或生物膜的滲透性與殺菌效用。

There were two main objectives in this study. One was to analyze the variation of microbial community of the biofilms formed on the outlet pipeline of the cooling water system with time. To determine the correlation between biofilm and corrosion of the system. The other aim was to investigate the corrosion process characteristics and the electrochemical behavior in the presence of thermophilic denitrifying Fe-oxidizing bacteria TPH-7.
According to the result of DGGE analysis, the corrosion of the system may be caused by the bacteria in the biofilms. The result showed that there were some kinds of bacteria existing in the biofilms, which were capable of oxidizing ferrous iron, adhering to surface or relating to corrosion.
Corrosion current decreasing with the increase of Na2MoO4 concentration was observed under the experimental conditions. When the concentration of Na2MoO4 was 100 ppm, molybdate could form oxide layer on surface to protect carbon steel. After exposure for 20 days, the corrosion current decreased to 7μA. However, the corrosion current was higher(42μA) and the weight loss increased after exposing for 20 days in the presence of strain TPH-7. This indicated that strain TPH-7 was capable of interfering with the inhibition of molybdate.
The results of long-term inhibitory effect of biocides indicated that suspended cells of strain TPH-7 could be inhibited by more than 50 ppm commercial biocide A or 100 ppm ClO2 within 1500 hours. But the 100 ppm biocides were ineffective to inhibit strain TPH-7 attaching to the surface of specimens, because the corrosion current was not lower.
The result of inoculating strain TPH-13-3 in addition to strain TPH-7 showed that MIC of strain TPH-7 was not stimulated significantly, because corrosion currents were not much more,
According to the above-mentioned description, the formation of biofilm must be inhibited to improve MIC problems of the cooling water system. Strain TPH-7 was competitive with molybdate for adsorption sites and could interfere with the corrosion inhibition process. Therefore, more Na2MoO4 may be required to inhibit MIC. The addition concentration of Na2MoO4 and biocides have to be tested before application.
URI: http://hdl.handle.net/11455/5150
其他識別: U0005-1307200616570900
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