廢水水質參數對半硝化反應之影響

Abstract

環保署已將氨氮納為晶圓製造及半導體製造業、光電及其製品製造業以及科學園區放流水標準管制項目之一。因此，對於國內高科技產業將產生重大影響。目前較新穎的氨氮處理技術為厭氧氨氧化（Anaerobic Ammonium Oxidation, Anammox）程序，此反應可將氨氮及亞硝酸氮直接反應生成氮氣，此反應具有不需添加碳源與相對少量曝氣、污泥產量低等諸多優點。相當適用於高科技產業之高氨氮濃度/低有機物濃度之廢水特性。 對於厭氧氨氧化系統來說，由於需要利用亞硝酸氮做為電子接受者，而將氨氮氧化成氮氣。因此，累積亞硝酸氮濃度為厭氧氨氧化反應中相當重要之前處理程序。半硝化是將氨氮利用氨氧化菌（ammonia oxidation bacteria, AOB）氧化成亞硝酸根離子，並同時抑制亞硝酸氮氧化菌（nitrite oxidation bacteria, NOB）之活性，以達到累積亞硝酸氮之目的。由於亞硝根離子為硝化過程的中間產物，因此，需不同於傳統硝化作用的控制條件來完成半硝化反應，以利於後續的除氮反應，此步驟的效能是影響後續厭氧氨氧化反應的關鍵。 本研究以4種控制參數（包含pH值、溶氧濃度、進流氨氮濃度及進流無機碳濃度）同時並利用分子生物技術鑑定其中AOB與NOB之族群變化，以評估對於達成半硝化累積亞硝酸氮的效果。實驗結果發現，pH及氨氮濃度的控制皆無法達成半硝化的目標。而DO在 0.2 mg/L的條件下，亞硝酸氮的累積率為52.3 %，顯示在低溶氧的條件下氨氧化菌的競爭優勢大於亞硝酸氮氧化菌。而無機碳的進流濃度控制在40 mg C/L的情況下，可讓系統中的亞硝酸氮累積率達到81.2 %，系統中氨氧化菌Nitrosomonas sp.的比例由62.1 %上升至74 %，亞硝酸氧化菌Nitrobacter sp. 的比例由20 %下降至3 %，Nitrospira sp.的比例由16.7 %降至2.1 %。由以上數據顯示，對於半硝化系統的控制，無機碳的限制，才是最主要的影響因子。 關鍵字：厭氧氨氧化、氨氧化菌、亞硝酸氮氧化菌、無機碳

Abstract Ammonia is one of the most important chemical applied in high-tech industries such as semi-conductor manufacturing and opto-electronic manufacturing processes. Thus, EPA of Taiwan regulated strict limitation of ammonia nitrogen with these two industries. Anaerobic ammonium oxidation (Anammox) process is a novel technology for ammonia removal. The biochemical reaction of Anammox is applied nitrite as electron acceptor and oxidized ammonia to nitrogen gas. Advantages of Anammox process includes no organic carbon addition, low oxygen demand and low waste sludge production. Thus, it is very suitable for ammonia wastewater treatment in the high-tech industry. Nitrite is electron acceptor of the Anammox process. How to accumulate nitrite before the Anammox process is very important. There are two main groups in nitrification reaction, one is ammonia oxidation bacteria (AOB) and the other is nitrite oxidation bacteria (NOB). Partial nitrification process created suitable environment for AOB rather than NOB, thus nitrite accumulation can be achieved. However, the operation parameter of partial nitrification is different from traditional nitrification process. Thus, the goal of this research is to find out suitable parameters such as pH value, ammonia concentration, dissolved oxygen concentration (DO) and inorganic carbon concentration of the partial nitrification reaction. Microbiology analysis is also applied to understand the composition of AOB and NOB in the partial nitrification system. The result of this research indicated that pH value, DO concentration and incoming ammonia concentration were minor operation parameters in the partial nitrification process. Highest nitrite accumulation rate is 52.3 % with pH value of 8.0, influent ammonia concentration of 400 mg/L and DO concentration of 0.2 mg/L. The inorganic carbon concentration is the most important parameter of this study. When the inorganic carbon concentration decreased from 146 mg C/L to 40 mg C/L, the nitrite accumulation rate can be increased obviously from 52.3 % to 81.2 %. The same result also can be found in the microbiology analysis. Composition of AOB (Nitrosomonas sp.) increased from 62.1 % to 74 % as well as composition of NOB (Nitrobacter sp. and Nitrospira sp.) decreased from 20 % to 3 % and 16.7 % to 2.1 %, respectively under low inorganic carbon concentration. Keywords: Anaerobic ammonium oxidation、ammonia oxidation bacteria、 nitrite oxidation bacteria、inorganic carbon