生物除氮程序氧化亞氮減排之研究

Abstract

在過度含氦污染物的廢水中氦的去除是極為重要地，如在環境中氨對於水生物種是具有 毒性的並且在自然界的水環境中造成優養化，嚴重地降低接受水體的水質。從生物技術 的角度來看，廢水中氦的去除是藉由硝化和脫硝兩種程序分別在獨立的反應槽中進行。 這種傳統的方法有許多缺點，最重要的為排放出的氧化亞氦(n2o)。n2o為溫室氣體潛 勢之一，而且全球的暖化潛勢為二氧化碳的310倍。因此，控制N2O排放到環境中是必 要地。厭氧氨氧化反應在除氦的領域中為最近的新突破。此反應為利用亞硝酸當作電子 的接受者在沒有產生N2O下直接將氨轉換成氦氣。然而，一些研究人員指出在厭氧氨氧 化反應處理廢水過程中會排放出n2o氣體。此外厭氧氨氧化程序的另一缺點為所需的亞 硝酸不存在於廢水中，必須結合部分硝化程序。CANON和SNAD為單槽式部分硝化 與厭氧氨氧化除氦中最符合成本效益的程序。SNAD程序中氨氧化菌，厭氧氨氧化菌和 脫硝菌在氧限制的條件下共同馴養。部分硝化過程中藉由氨氧化菌在氧限制條件下誘導 N2O排放。SNAD程序中存在的脫硝菌也被指出凡0的排放。然而，到目前為止沒有研 究或文獻報告有關於在SNAD程序中N2O的估計與控制。因此，本提案的主要目標為 探討並估計在SNAD生物除氦程序過程中N20的排放。發展最佳的物化條件使得N20 的排放量降到最低並且研究在反應槽中微生物族群分佈的鑑定與多樣性，在這些最佳條 件下發展單槽式部分硝化與厭氧氨氧化反應之永續性生物除氦程序為本計劃其它主要 的目標。

Nitrogen removal from wastewaters is extremely important as excessive nitrogen pollutants

such as ammonia in environment are toxic to aquatic species and causes eutrophication in

natural water environments and severe reductions in water quality in receiving water bodies.

Biologically, nitrogen is removed from the wastewater by nitrification and denitrification

process using two separate reactors. This tradition method has several disadvantages and the

most important one is emission of nitrous oxide (N2O). N2O is one of the potential greenhouse

gases and its global warming potential is about 310 times more powerful than CO2. Therefore,

it is essential to control the emission of this gas into the environment. Anaerobic ammonia

oxidation (anammox) reaction is the recent advancement in the field of nitrogen removal. This

reaction directly converts ammonia into di nitrogen gas using nitrite as electron acceptor

without producing N2O. However, some researchers reported N2O emission from anammox

reactor during wastewater treatment. Moreover, requirement of nitrite, which is not present in

wastewater, is another disadvantage of anammox process and it is necessary to combine

anammox process with partial-nitrification process. CANON (completely autotrophic

nitrogen removal over nitrite) and SNAD (simultaneous partial nitrification, anammox and

denitrification) are the two most cost effective single reactor nitrogen removal processes

based on combined partial -nitrification and anammox reaction. In these processes, aerobic

ammonia oxidizing bacteria (AOB), anammox bacteria and denitrifying bacteria (in case of

SNAD process) are cultivated together under oxygen limited conditions. Oxygen limited

conditions during partial-nitrification induce N2O emission by AOB. The presence of

denitrifying bacteria in case of SNAD process also indicates the emission of N2O. However,

no study or report available in literature regarding the estimation and control of N2O emission

from SNAD process. Therefore, the main objective of this proposal is to study and estimate

the emission of N2O during the biological nitrogen removal by SNAD process. Development

of optimum physical-chemical conditions for minimum emission of N2O and studies on

diversity and identification of microbial community in the reactor system under these

optimum conditions are the other major objectives of this project to develop a sustainable

single reactor biological nitrogen removal process based on partial-nitrification-anammox

reactions.