由於水中的含氮污染物是目前最受到關切的污染物之一，其過度排放皆會對環境造成污染甚至對人體造成危害，加上我國政府對於環保法規的重視，對污水處理廠排放標準採用更高標準之放流水水質管制。由於在污水處理廠中大多以異營性微生物進行脫硝作用，但在處理無機廢水則需要添加額外有機碳源才能有較好的脫硝效果，因此發展出可直接利用無機性電子供體之自營性微生物以進行脫硝反應，其優點包含不需要添加額外機有機物和產生污泥量較低。
本研究以硫代硫酸鹽作為自營性脫硝系統之無機性電子供體，並探討此活性污泥最合適之 S/N 比，以及對自營性脫硝進行不同 pH 值與溶氧濃度之影響比較。結果顯示當 S/N 比 = 2.19 時，自營脫硝微生物有足夠之電子供體可進行完全脫硝反應，並且不會有中間產物累積；但當 S/N 比 = 1.88 時，則脫硝微生物則會優先還原硝酸鹽氮，造成亞硝酸鹽氮累積現象產生。在本研究中所培養之自營脫硝污泥，其組成以 Sulfurimonas 與 Thiobacillus 這兩株硫脫硝菌群為主並占了整體一半以上。
在 pH 對自營性脫硝影響方面可得知在 pH = 7 時，脫硝速率達到最大值，並且在 pH = 6 ~ 8 之間都具有將硝酸鹽氮完全去除且不會有中間產物累積，此時的比脫硝速率平均為 7.69 mg NO3--N/g VSS*hr；而當 pH < 6 或是 > 8 時，則脫硝效率則會受到限制，在 pH = 5 與 9 時比脫硝速率分別為 1.66 及 4.12 mg NO3--N/g VSS*hr，並且硝酸鹽氮大部分僅還原成亞硝酸鹽氮並累積。
在溶氧濃度影響上，當系統處於缺氧狀態（DO = 0 mg/L）時，其脫硝速率達最佳狀態並可完全脫硝；在微好氧（DO = 1 mg/L）條件下，儘管硝酸鹽氮在反應結束時完全被還原，但大部分都以亞硝酸鹽氮累積在水體中；在好氧（DO = 3 mg/L）條件下脫硝作用則受到嚴重抑制現象。

關鍵字：自營性脫硝、還原性硫化物、S/N 比、pH、溶氧

Since nitrogen pollutants in water are one of the most concerned pollutants at present, their excessive discharge will cause pollution to the environment and even harm the human. In addition, the government attaches great importance to environmental protection regulations, discharge standards use higher standards for discharge water quality control. Since the heterotrophic denitrification bacteria are mostly used for denitrification in wastewater treatment plant, but need to add additional organic carbon source to have better denitrification effect when treating inorganic wastewater. Therefore, autotrophic denitrification bacteria have been developed for denitrification, which have advantages such as no need to add additional organic matter and lower sludge production.
In this study, thiosulfate was used as the inorganic electron donor in the sulfur autotrophic denitrification (SADN) system, and find the most suitable S/N ratio, also compare the effects of different pH values and dissolved oxygen concentrations in SADN. The results shown that when the S/N ratio = 2.19, the autotrophic denitrification sludge have enough electron donors to do the denitrification reaction, and there will be no accumulation of intermediate products; when the S/N ratio = 1.88, the nitrate in autotrophic denitrification will be preferentially reduced, lead to the nitrite will be accumulation. In addition, the autotrophic denitrification sludge domesticated in this study was mainly composed of Sulfurimonas and Thiobacillus, which accounted for more than half of the total.
The effect of pH in autotrophic denitrification reveal that denitrification rate reaches maximum at pH = 7, and between pH = 6 ~ 8, nitrate can be completely removed without intermediate product accumulation, and the average specific denitrification rate (SDNR) at this time is 7.69 mg NO3--N/g VSS*hr; when pH < 6 or > 8, the denitrification efficiency restricted, the specific denitrification rates were 1.66 and 4.12 mg NO3--N/g VSS*hr at pH = 5 and 9, respectively. Moreover, most of the nitrate was reduced to nitrite and accumulated.
The effect of dissolved oxygen concentration, shown that when the system is in anoxic stage (DO = 0 mg/L), the denitrification rate reaches the best performance and can completely denitrify. Under microaerobic conditions (DO = 1 mg/L), although nitrate is completely reduced at the end of the reaction, most of it is accumulated to nitrite. However, denitrification was severely inhibited under aerobic conditions (DO = 3 mg/L).

Keyword: autotrophic denitrification, reduced inorganic sulfur compounds, S/N ratio, pH, dissolved oxygen

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