| 摘要: | 氮污染是水體中的主要污染源之一，過量排放會危害環境與健康，因此我國政府逐步提高氨氮與總氮的排放標準，目前台灣多數廢污水處理廠採異營脫硝，但處理無機或低C/N比污水時，需額外添加有機碳源，不但增加操作成本且易引發二次污染問題。因此，近年來自營性脫硝因使用無機性電子供體，且無需外加有機碳源，受到關注與應用，現今進一步結合厭氧銨氧化技術，可提升整體脫氮效率、減少對有機碳源的依賴，並達到降低能源消耗與污泥產量的雙重目標。
本研究以硫代硫酸鹽做為電子供體，於長期試驗中探討硫自營性脫硝反應中，如何控制亞硝酸鹽氮之產生量，理論完全脫硝S/N莫耳比為1.56，因此控制S/N比以不足夠的硫源進行部分脫硝(Partial Denitrification, PD)產生亞硝酸鹽氮，在階段II當S/N比在1.1以下時，因為電子供體不足，無法進行硝酸鹽氮還原反應，當S/N比為1.3時，反應即可達完全脫硝，完全脫硝與厭氧銨氧化對總氮去除的貢獻率平均為13 %與87 %；在第IV階段中，S/N比為0.9時，系統仍可維持穩定脫氮效果，此一現象與微生物群落有關。
批次試驗中以不同S/N比與溫度進行特性探討，硫代硫酸鹽皆在反應初期迅速消耗，於出流水中檢測出亞硫酸鹽濃度，因此推測在反應中發生歧化反應(Branched Thiosulfate Oxidation, BTO)；在30 ℃條件下，S/N= 1.3表現出最佳氮去除效果，進一步將溫度提升至40 ℃時，脫硝與氨氮氧化速率皆顯著提升，證明溫度增加可以加快反應速率；當溫度下降至20 ℃或上升至45 ℃時硝酸鹽氮與氨氮皆無法有效去除，表明低溫與高溫條件下會抑制微生物活性。
於第III與IV階段進行微生物群落分析，厭氧銨氧化菌主要以Candidatus Brocadia為主，Thiobacillus為硫自營脫硝中的優勢菌屬，兩者的相對豐度皆於第IV階段增加至19 %與6 %，亦於第III階段另檢測出OLB8，其為脫硝相關菌屬被認為是不完全脫硝菌，主要將硝酸鹽氮還原為亞硝酸鹽氮，在厭氧銨氧化反應中扮演著關鍵角色；OLB13的存在與氮轉化效率有關，能與厭氧銨氧化菌形成協同作用。
;Nitrogen pollution is one of the major contaminants in aquatic environments. Excessive nitrogen discharge poses risks to both ecosystems and human health. In response, the Taiwanese government has progressively tightened the effluent standards for ammonia nitrogen and total nitrogen. Currently, most wastewater treatment plants in Taiwan adopt heterotrophic denitrification processes. However, for the treatment of inorganic or low C/N ratio wastewater, the addition of external organic carbon sources is required, which not only increases operational costs but may also lead to secondary pollution. Therefore, autotrophic denitrification, which utilizes inorganic electron donors and does not require external organic carbon, has gained increasing attention and application in recent years. The integration of anaerobic ammonium oxidation (Anammox) technology further enhances total nitrogen removal efficiency, reduces dependence on organic carbon, and achieves the goals of lowering energy consumption and sludge production.
In this study, thiosulfate was used as the electron donor to investigate how to control nitrite nitrogen accumulation during sulfur-based autotrophic denitrification in a long-term experiment. The theoretical S/N molar ratio for complete denitrification is 1.56. Therefore, by limiting the sulfur source (S/N < 1.56), partial denitrification (PD) was induced to promote nitrite nitrogen accumulation. In phase II, nitrate nitrogen accumulation was observed when the S/N ratio was below 1.1. At an S/N ratio of 1.3, complete denitrification was achieved, with denitrification and anammox contributing up to 13 % and 87 % of total nitrogen removal, respectively, indicating that nitrogen was primarily removed via the anammox pathway. In phase IV, the system maintained stable nitrogen removal even at an S/N ratio of 0.9, which was associated with shifts in the microbial community.
In the batch experiments, the characteristics of the system were investigated under various S/N ratios and temperatures. Thiosulfate was rapidly consumed during the initial stage of the reaction under all conditions. Due to the detection of sulfite in the effluent, it is inferred that a branched thiosulfate oxidation (BTO) pathway occurred during the reaction. Under 30 °C conditions, the S/N ratio of 1.3 exhibited the highest nitrogen removal efficiency. When the temperature was further increased to 40 °C, both the denitrification and ammonium oxidation rates were significantly enhanced, confirming that elevated temperature can accelerate the reaction rate. However, at lower (20 °C) or higher (45 °C) temperatures, nitrate and ammonium could not be effectively removed, indicating that both low and high temperature conditions inhibit microbial activity.
Microbial community analysis was conducted during Stages III and IV. Candidatus Brocadia was identified as the dominant genus of anammox bacteria, while Thiobacillus was the predominant genus involved in sulfur-based autotrophic denitrification. The relative abundances of these two genera increased in Stage IV, reaching 19 % and 6 %, respectively. In addition, OLB8 was detected in Stage III. This genus, associated with denitrification, is considered an incomplete denitrifier that mainly reduces nitrate to nitrite, playing a key role in supporting the anammox process. The presence of OLB13 was also observed and is believed to be related to nitrogen transformation efficiency, potentially forming a synergistic relationship with anammox bacteria. |
