厭氧微生物技術之硫酸還原與氨氧化

Abstract

台灣半導體產業蓬勃發展，製程的廢水含有高濃度的氨氮與硫酸根，其低pH與低BOD含量的廢水特性，增加園區污水處理設施的負荷。 傳統的除氮程序包含完全硝化(氨氮完全氧化為硝酸鹽氮)，再結合脫硝程序(利用有機碳供應電子，將硝酸鹽氮還原成氮氣)，研究指出處理1毫克的氨氮，需供應4.5毫克的溶氧，為了供應足夠氧氣予微生物作利用，需耗費大量電能驅動曝氣幫浦，且有機物會轉變為溫室氣體並溢散至環境，完全背離環境友善的理念。 取代傳統程序的 Nitritation/Anammox 厭氧除氮程序，可節省 60% 電能消耗，又不需有機物，代表零溫室氣體排放，現行最具效益的厭氧除氮程序。 根據不同的廢水特性，有研究認為節省 100% 電能消耗是可能達成的，將 Nitritation 需要的自由氧以硫酸根的結合氧取代，再結合Anammox的新程序，已被命名為「硫酸還原與氨氧化(Sulfate Reduction and Ammonium Oxidation, SRAO)」。 本研究操作1公升的連續上流式厭氧反應槽，固定水力停留時間為7天，操作時程達750日，氨氮與硫酸的進流負荷分別為 23 g N m-3 d-1與 14 g S m-3 d-1，莫耳比約為 NH4+:SO42- = 4:1，pH控制在8.5。 此培養條件的氨氮去除效率最高可達 98% 、去除速率約為22.5 g N m-3 d-1，亞硝酸鹽氮的累積速率約為0.4 g N m-3 d-1、硝酸鹽氮的累積速率約為 3 g N m-3 d-1；並以 qPCR 分子生物技術，定性與定量槽內的微生物種，結果發現長時間培養後， Anammox 成功的從弱勢轉為優勢菌群，原先具有優勢的 AOB、NOB明顯減少，礙於缺乏 SRAO 細菌的相關資訊，現有的分析技術還無法確定其含量增加與否。

Semiconductor industries in Taiwan generates high ammonium and sulfate containing wastewaters which creates complication of the industrial park wastewater treatment plant due to its wastewater characteristics, i.e., lower pH, no/low biological oxygen demand (BOD). Ammonium removal is an energy intensified process for every mg of ammonium, 4.5 mg of dissolve oxygen is required for microorganisms. Traditional nitrogen removal involves nitrification (oxidation of ammonium to nitrite then nitrate) following by denitrification (reduction of nitrate to nitrite then nitrogen with organic carbon as electron donor). These multistep biochemical process not only require energy for aeration but organic carbon will transform into green-house gas. Nitritation/Anammox process instead of traditional process can save 60% of energy consumption and no added organic matters means without green-house gas emission in recent years. According the different wastewater characteristics, new process have been published which can save 100% of energy use. Using sulfate instead of free oxygen oxidizing ammonium to nitrite in Nitritation process and combining with Anammox process to nitrogen gas is hypothesized that call “Sulfate Reduction and Ammonium Oxidation (SRAO)”. This research operating a continuous upflow reactor with one litre volume under hydraulic retention time is seven days. The average ammonium and sulfate loading rate are 23 g N m-3 d-1 and 14 g S m-3 d-1, respectively. Molar ratio of influent NH4+:SO42- about 4:1 and control the pH value around 8.5. The average ammonium removal efficiency is 98% and removal rate about 22.5 g NH4+-N m-3 d-1 after 750 days cultured, and accumulate rate of nitrite and nitrate are 0.4 g NO2- -N m-3 d-1 and 3 g NO3- -N m-3 d-1, respectively. Using quantitative real time polymerase chain reaction (qPCR) to quality and quantity the microorganisms that a kind of molecular biotechnology and the results shows Anammox definitely is dominant bacteria than AOB, NOB and others after long term cultured. Unfortunately, biological information of SRAO bacteria still rare that lead to can’t ensure its quality and quantity yet.