不同光強度與無光對照下藻菌顆粒污泥之成長與污染物去除效能比較

Abstract

藻菌顆粒污泥(Algae-Bacterial Granular Sludge, ABGS)結合藻類光合作用與好氧顆粒污泥(Aerobic Granular Sludge, AGS)之高沉降性，具有同步去除有機物、氮磷營養鹽及降低溫室氣體排放之潛力。然而，ABGS系統高度依賴光照條件，適當光照有助於藻類生長與藻菌共生，但過高光強度可能造成藻類過度增殖、顆粒鬆散或沉降性下降，而光照不足則可能限制藻類活性。因此，本研究以光強度為主要變因，設置三組序批式反應槽，分別為A槽高光ABGS組(120 μmol·m⁻²·s⁻¹)、B槽低光ABGS(60 μmol·m⁻²·s⁻¹)及C槽無光AGS對照組(0 μmol·m⁻²·s⁻¹)，以比較不同光照條件對顆粒成長、污染物去除、胞外聚合物(Extracellular Polymeric Substances, EPS)累積及溫室氣體生成之影響。 結果顯示，高光條件可於操作前中期促進藻類與生物量快速累積，使顆粒粒徑增大，並提升總氮與總磷去除表現；然而，長期操作下過大的顆粒可能導致顆粒老化或局部崩解，使後期顆粒穩定性下降。相較之下，低光條件雖未形成最大粒徑顆粒，但粒徑變化較平緩，且後期EPS明顯增加，顯示低光條件較有利於維持ABGS長期穩定。無光AGS雖可快速形成穩定顆粒並維持污染物去除，但其N₂O與CO₂累積量明顯高於ABGS，而CH₄於三槽中皆未出現明顯累積。 綜合各項指標，ABGS相較於無光AGS具有較高EPS累積及較低N₂O與CO₂生成之優勢，顯示藻菌共生系統有助於提升顆粒結構穩定性並降低溫室氣體排放。其中，B槽低光ABGS在長期穩定性、污染物去除及溫室氣體減量之間具有較佳平衡，其平均溶解性化學需氧量、總氮及總磷去除率分別為96.01±2.62%、55.46±10.52%及74.91±17.16%，為本研究中較適合長期操作之光照條件。

Algae-bacterial granular sludge (ABGS) combines algal photosynthesis with the high settleability of aerobic granular sludge, showing potential for simultaneous organic matter removal, nitrogen and phosphorus removal, and greenhouse gas mitigation. However, the performance of ABGS is highly dependent on light conditions. Appropriate light intensity can promote algal growth and algae–bacteria symbiosis, whereas excessive light intensity may cause algal overgrowth, granule loosening, and deterioration of settleability. In contrast, insufficient light may limit algal activity. Therefore, this study used light intensity as the main operational variable and established three sequencing batch reactors: reactor A as the high-light ABGS group (120 μmol·m⁻²·s⁻¹), reactor B as the low-light ABGS group (60 μmol·m⁻²·s⁻¹), and reactor C as the dark AGS control group (0 μmol·m⁻²·s⁻¹). The effects of different light conditions on granule growth, pollutant removal, EPS accumulation, and greenhouse gas production were compared. The results showed that high-light conditions promoted rapid algal and biomass accumulation during the early and middle operation stages, resulting in increased granule size and improved total nitrogen (TN) and total phosphorus (TP) removal. However, under long-term operation, oversized granules may lead to granule aging or partial disintegration, thereby reducing granule stability in the later stage. In comparison, although the low-light condition did not produce the largest granules, it maintained a more stable granule size distribution, and EPS increased markedly in the later stage, indicating that low-light conditions were more favorable for maintaining long-term ABGS stability. Although the dark AGS group rapidly formed stable granules and maintained stable pollutant removal, its N₂O and CO₂ accumulation was markedly higher than that of the ABGS groups, while CH₄ showed no obvious accumulation in all three reactors. Overall, compared with dark AGS, ABGS showed higher EPS accumulation and lower N₂O and CO₂ production, suggesting that algae-bacteria symbiosis contributed to enhanced granule structural stability and reduced greenhouse gas emissions. Among the three systems, the low-light ABGS in reactor B showed a better balance among long-term stability, pollutant removal, and greenhouse gas mitigation. The average soluble chemical oxygen demand, TN, and TP removal efficiencies of reactor B were 96.01 ± 2.62%, 55.46 ± 10.52%, and 74.91 ± 17.16%, respectively, indicating that low-light ABGS was the more suitable condition for long-term operation in this study.