| 摘要: | 氮為污水排放中常見物質，達一定濃度將使生態與人體造成危害，而我國法規以漸進式加嚴管制，從民國 110 年至 116 年期間將減少氨氮 70% 放流濃度，氨氮經硝化反應後將轉換成硝酸鹽氮存在水中，目前大部分均採異營性脫硝反應將其轉換為氮氣，然而部分污水因碳源不足使其脫硝效果不佳，因此近年來興起自營性脫硝，以無機物作為電子供體，不需額外補充有機物，同時減少污泥產量。
本研究以硫代硫酸鹽作為電子供體，於長期試驗中進行 SBR 與 SBBR 反應性能比較，HDPE 生物擔體經 108 天馴養後，因擔體表面光滑使擔體間剪切力較強，導致生物膜產生量不盡理想，因此 SBBR 無法有效提升反應器內生物量與氮負荷。
批次試驗中以不同S/N 比進行特性探討，與長期試驗皆觀察到當硫代硫酸鹽充足時，將使歧化硫代硫酸鹽氧化反應（branched thiosulfate oxidation, BTO）發生，促使硫代硫酸鹽還原元素硫後累積於污泥表面，因此 S/N 莫耳比需大於理論值的 1.36 倍（2.19）以上才具有足夠的電子供體達完全脫硝，若 S/N 莫耳比降至理論值 1.1 倍（1.75），因歧化反應導致硫代硫酸鹽不足，部分亞硝酸鹽氮將使用累積元素硫進行反應，與硫代硫酸鹽相比，元素硫反應速率僅為其 0.17 倍。亞硝酸鹽氮的累積主要受到 S/N 比所控制，並且根據所使用還原性硫化物之反應特性將改變反應速率，於足夠 S/N 比下氮濃度變化呈 0 階反應，並隨著電子供體濃度下降，逐漸由 0.5 階轉變至 2 階反應。而本研究以單次進流進行試驗，因此不論 S/N 比的多寡，皆有歧化反應的進行，平均硫轉換率僅達 70%。
菌相組成中將試驗結束與初期相比，Thiobacillus 比例增加近一倍，Sulfurimonas 佔比下降 10%，自營脫硝菌群均佔 70%以上，亦有觀察到歧化反應菌群 Desulfobacterota，佔比 1.5%。
;Nitrogen is a common substance found in wastewater discharges. When it reaches a certain concentration, it can cause harm to ecosystems and human health. In Taiwan, regulations have been progressively tightened. From the year 2021 to 2027, there will be a 70% reduction in the discharge concentration of ammonia. Ammonia undergoes nitrification and converts into nitrate, which exists in water as nitrate ions. Most wastewater treatment systems employ heterotrophic denitrification to convert nitrate into nitrogen gas. However, some wastewater treatment plants experience poor denitrification efficiency due to insufficient carbon sources. In recent years, autotrophic denitrification has gained popularity as it uses inorganic substances as electron donors, eliminating the need for additional organic matter and reducing sludge production.
In this study, thiosulfate was used as an electron donor to compare the performance of sequencing batch reactors (SBR) and sequencing biofilm batch reactors (SBBR) in long-term experiments. After 108 days of domestication, the HDPE biofilm carriers did not achieve the desired biofilm formation due to their smooth surface and strong shear forces between the carriers. Therefore, SBBR could not effectively increase the reactor′s biomass and nitrogen loading rate.
In the batch test, the kinetics of the S/N ratio were investigated at different nitrogen loading rate. Both the long-term and batch test observed that when sufficient thiosulfate was present, the branched thiosulfate oxidation (BTO) reaction will occur. Resulting in the accumulation of elemental sulfur on the sludge surface after the reduction of thiosulfate.
Therefore, the S/N molar ratio needs to be maintained above 1.36 times (2.19) than theoretical value to provide enough electron donors for complete denitrification. If the S/N molar ratio decreases to 1.1 times than theoretical value (1.75), some nitrite will use accumulated elemental sulfur to reduce. Compared to thiosulfate, the reaction rate of elemental sulfur is only 0.17 times. In this study, single inflow experiments were conducted, so regardless of the S/N ratio, the BTO reaction occurred, resulting in an average sulfur conversion rate of only 70%. The accumulation of nitrite is mainly controlled by the S/N ratio and the characteristics of the different sulfur sources, which also alter microbial activity. Under sufficient S/N ratio, the change in nitrogen concentration follows zero-order kinetics, and as the electron donor concentration decreases, it gradually transitions to 0.5th t2nd-order kinetics.
In terms of microbial abundance, compared to the initial phase, Thiobacillus proportion increased by nearly twofold, while Sulfurimonas decreased by 10%. Autotrophic denitrifying bacteria accounted for more than 70%, and the presence of BTO bacteria Desulfobacterota was observed, accounting for 1.5% of the microbial community. |
