運用模廠規模生物濾床去除污水處理廠沼氣中的硫化氫

Abstract

厭氧消化產生的沼氣可以做為發電機的使用能源，但是沼氣組成中的硫化氫成分會對發電機組造成影響，造成發電機組損害，無法有效利用沼氣進行發電，而透過生物脫硫可以有效降低沼氣中硫化氫的濃度，達到純化沼氣的功效。 本研究藉由在污水處理廠設置模廠規模的生物濾床，並運用實廠中經厭氧發酵而產生的沼氣作為生物濾床沼氣脫硫的實驗對象，將經本研究控制的參數變化與硫化氫的去除效率進行比較，並同時將填充載體進行菌相分析、元素分析以及觀察掃描式電子顯微鏡，將實驗結果進行整理可做為實廠使用建議。 生物濾床中添加拉西環以及發泡煉石作為生物載體，並在預實驗階段決定氧氣的進氣濃度以及質淋洗頻率。在氧氣進氣濃度為 3 % 以及基質淋洗頻率為兩天一次的條件下，可以使生物濾床有穩定的運行效果。在為期將近5個月的運行時間下，透過改變沼氣進流負荷的條件 (15, 30, 60 L/min )，找到最適合的沼氣停留時間，在停留時間為7.28 - 14.56 min，生物濾床可以達到去除率有85 %的穩定運行狀況。 採集在模廠規模生物濾床運行100天的載體進行菌相分析，生物濾床在運行期間會產生硫酸根以及氫離子使得濾料產生酸化，因此整體環境讓嗜酸菌更適合生存，而參照菌相分析的結果在生物濾床內部主要為 Acidithiobacillus 以及 Sulfobacillus 為內部主導的菌群，與實際操作的結果相符合，主要都是以嗜酸菌為主。 在各項現場的運行參數使硫化氫去除率達穩定後，為了提供未來實廠運用的操作便利性，將進流基質的來源從原先實驗室自行條配的基質轉變為使用合作污水處理廠的初沉池出流水，在更換進流基質後，而為了彌補兩者進流基質的差異，提升添加體積以維持營養源的濃度，在採用初沉池出流水的生物濾床經過此調整後，硫化氫的去除率可以維持在高於 90 % 的理想狀況。 綜合了本研究在污水處理廠的模廠試驗中試驗了各項操作參數包含停留時間、氧氣濃度、進流基質成分以及基質淋洗頻率後，生物濾床的去除率保持穩定有效的結果，本研究可以供未來實廠運作生物濾床的參考建議。

Anaerobic digestion produces biogas that can be used as a source of energy for generators. However, the presence of hydrogen sulfide in the biogas composition can have adverse effects on generator units, leading to damage and ineffective use of biogas for power generation. Through the process of biological desulfurization, the concentration of hydrogen sulfide in biogas can be effectively reduced, achieving the purification of biogas. This study set up a pilot-scale biological filter bed at a wastewater treatment plant and used biogas generated through anaerobic fermentation as the subject of the biological desulfurization experiment. The study compared the variations in controlled parameters with the efficiency of hydrogen sulfide removal. Additionally, the study analyzed the microbial community, conducted elemental analysis, and observed scanning electron microscopy of the filled carriers, providing valuable data for practical plant recommendations. The biological filter bed was supplemented with Lasiococcus and expanded perlite as biological carriers. During the pre-experimental phase, the oxygen inlet concentration and substrate leaching frequency were optimized. Under the conditions of 3% oxygen inlet concentration and a substrate leaching frequency of once every two days, the biological filter bed demonstrated stable performance. By adjusting the biogas inlet flow rates (15, 30, 60 L/min) over a period of nearly five months, the optimal biogas retention time was determined, which ranged from 7.28 to 14.56 minutes, ensuring the stable operation of the biological filter bed. Microbial community analysis was performed on the carriers collected from the pilot-scale biological filter bed after 100 days of operation. The operation of the biological filter bed led to acidification of the filter material, creating an environment conducive to the survival of acidophilic bacteria. The results of the microbial community analysis revealed that Acidithiobacillus and Sulfobacillus were the dominant bacterial species inside the biological filter bed, aligning with the actual operational findings, indicating a prevalence of acidophilic bacteria. Once the operational parameters for stable hydrogen sulfide removal were established on-site, to facilitate future practical implementation, the source of the influent substrate was changed from laboratory-prepared media to the effluent from the primary settling tank of a cooperative wastewater treatment plant. To compensate for differences in the influent substrate, the addition volume was increased to maintain the nutrient concentration. After making these adjustments, the biological filter bed using the effluent from the primary settling tank maintained an ideal hydrogen sulfide removal efficiency of over 90%. In conclusion, this study conducted various operational parameter tests, including retention time, oxygen concentration, influent substrate composition, and substrate leaching frequency, on a pilot-scale biological filter bed at a wastewater treatment plant. The results demonstrated stable and effective hydrogen sulfide removal rates, providing valuable recommendations for the future operation of biological filter beds in practical settings.