Effects of ammonium loading rate on the treatment of wastewater containing TMAH by CANON process
|關鍵字:||CANON程序;氨氮負荷;氫氧化四甲基銨;除氮效率;CANON process;ammonium loading;TMAH;nitrogen removal|
|摘要:||現今高科技產業發展蓬勃，在光電產業中薄膜電晶體液晶顯示器(Thin film transistor liquid crystal display, TFT-LCD)的製程中會產生大量的廢水，其中高達三分之一屬有機廢水，主要成分之一為氫氧化四甲基銨(Tetramethylammonium hydroxide, TMAH)這個具有毒性的含氮有機物質，進入自然水體系統會危害水體中生物且人體經接觸嚴重時可能導致受體死亡，現行法規下水道可容納排入標準為30 mg/L，因此有效處理含氮有機物的廢水是一項挑戰。
相較於傳統完全硝化脫硝的除氮流程，厭氧氨氧化(Anaerobic ammonium oxidation, Anammox)的除氮步驟更具經濟效益，可以節省60%的氧氣需求量、90%的污泥處理成本和100%的有機碳源，Anammox作用需要結合部分硝化的步驟，使氨氮氧化成亞硝酸鹽氮，將其做為Anammox 菌的電子接受者，而Completely Autotrophic Nitrogen removal Over Nitrite (CANON)系統正是於在單一槽體中結合了部分硝化以及厭氧氨氧化的流程。
本研究以缺氧上流式反應槽進行，實驗初期以TMAH和氨氮之合程廢水進流，在過程中階段性改變進流氨氮負荷，之後將TMAH改以實廠廢水進流，實驗中同時監測其出流水水質，結果顯示厭氧氨氧化菌在進流氨氮和TMAH比為900：2000及500：2000 (mg/L)時的仍可保持高的除氮效率，而當氨氮和TMAH比為200:2000 (mg/L)時除氮效率顯著下降，在長期操作改以實廠廢水進流搭配額外添加之氨氮200 mg-N/L後，厭氧氨氧化菌已變成沒有活性，經分子生物技術測定，此時的微生物族群主要為TMAH之降解菌和脫硝菌為主，推測除氮路徑從厭氧氨氧化過程轉變為脫硝流程，而在實驗進行期間即使氮去除效率不佳，TMAH的平均去除效率仍高達97.8%。|
Semiconductor and thin film transistor liquid crystal display (TFT-LCD) are two of the most important industries in Taiwan. Tetramethylammonium hydroxide (TMAH) is widely used as developers in TFT-LCD manufacturing processes. Then, it will produce a large quantity of organic nitrogen wastewater containing high concentrations of TMAH. TMAH is a bio-toxic compound, it can result in many symptoms, such as muscle convulsions, causing difficulties in breathing, and possibly death. Therefore, it is important to treat the TMAH-containing wastewater before being discharged to the environment. Compared with the traditional nitrogen removal process, the anammox process is more economical. It can save 60% aeration, 90% sludge treatment cost and 100% cost for adding organic carbon. Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process is a system that ammonium is oxidized to nitrite by AOB, and the nitrite and part of ammonium are converted to nitrogen gas under oxygen-limiting by anammox bacteria in a single reactor. The effect of TMAH on the nitrogen removal efficiency with different ammonium concentration by a CANON process in a continuous anoxic upflow bioreactor. Results indicated that the average ammonium and total nitrogen removal efficiency were 88% to 98% and 86% to 95% when the ammonium concentration was 500 to 900 mg-N/L with 2000 mg/L synthetic TMAH wastewater. The ammonium and total nitrogen removal efficiencies decreased to 78% and 66%. In the third stage, the reactor was fed with real wastewater containing TMAH. The condition didn't become better and the ammonium and total nitrogen removal efficiency also decreased. The results of biotechnology demonstrated the evidences of the inhibition of anammox in the second and third stage, while the average removal efficiencies of TMAH were 97.8% and intermediates (TMA, DMA, MA and TMAO) were not detected during the whole operational conditions. We finally supposed the nitrogen removal process changed from anammox process to denitrification.