Shandong Provincial Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong 266237, China.
Department of Stomatology, Qilu Hospital of Shandong University, Qingdao, Shandong 266035, China.
Sci Total Environ. 2020 Jun 20;722:137660. doi: 10.1016/j.scitotenv.2020.137660. Epub 2020 Mar 2.
High salinity and low temperature are generally considered to have negative effects on the formation, stability and performance of aerobic granular sludge (AGS). This study investigated whether and how salinity acclimation strategies can enhance aerobic granulation at low temperature (12 °C) in three sequencing batch reactors (SBRs). Stepwise increased concentrations of NaCl (2-10 and 4-20 g/L) were added to the influent of R1 and R2 with steps of 1 and 2 g/L per week respectively, while R0 was set as a control (salt-free). The granulation processes in R1 and R2 were rapidly started up within 9 days, and were completed within 21 and 18 days, respectively. By contrast, R0 took 25 days and 49 days to start and complete granulation. The salinity acclimation strategies improved sludge hydrophobicity, reduced repulsion barrier between cells, and stimulated EPS production during granulation processes, which simultaneously promoted the formation of AGS. When the influent salinity reached 14 g/L on day 35, granule hydrophobicity, density and size in R2 sharply decreased and granules began to disintegrate afterwards. When operated under salt-free condition, sludge bulking occurred in R0 since day 60. The treatment performance was thus impaired in these two reactors, especially in R2 with significant biomass loss. Conversely, the AGS developed in R1 maintained stable structure with high biomass concentration (8.0 gSS/L) and excellent treatment performance for COD (90%), ammonium (95%) and total nitrogen (70%). Genera Thauera, Azoarcus, and Nitrosomonas were more enriched, while Flavobacterium and Meganema were more suppressed in R1, which would have contributed to granule stability and treatment performance. In conclusion, great care has to be taken for cultivating and operating AGS at low temperature for treating saline wastewater. Increasing salinity with a lower salt gradient provides a possibility for rapid granulation of AGS with excellent treatment performance under such conditions.
高盐度和低温通常被认为会对好氧颗粒污泥（AGS）的形成、稳定性和性能产生负面影响。本研究探讨了在三个序批式反应器（SBR）中，盐驯化策略是否以及如何能够在低温（12°C）下增强好氧颗粒化。R1 和 R2 的进水逐步增加 NaCl 浓度（分别为 2-10 和 4-20 g/L），每周增加 1 和 2 g/L，而 R0 则作为对照（无盐）。R1 和 R2 的颗粒化过程在 9 天内迅速启动，分别在 21 和 18 天内完成。相比之下，R0 启动和完成颗粒化分别需要 25 天和 49 天。盐驯化策略提高了污泥疏水性，减少了细胞间的排斥障碍，并在颗粒化过程中刺激了 EPS 的产生，同时促进了 AGS 的形成。当进水盐度在第 35 天达到 14 g/L 时，R2 中的颗粒疏水性、密度和粒径急剧下降，随后颗粒开始解体。在无盐条件下运行时，R0 从第 60 天开始出现污泥膨胀。因此，这两个反应器的处理性能受到了影响，尤其是在 R2 中，生物量损失显著。相反，在 R1 中形成的 AGS 保持稳定的结构，具有高生物量浓度（8.0 gSS/L）和出色的 COD（90%）、氨氮（95%）和总氮（70%）去除效果。属 Thauera、Azoarcus 和 Nitrosomonas 更丰富，而 Flavobacterium 和 Meganema 则受到更多抑制，这有助于颗粒的稳定性和处理性能。总之，在低温下培养和操作 AGS 来处理含盐废水需要非常小心。以较低的盐梯度增加盐度为在这种条件下快速形成具有出色处理性能的 AGS 提供了可能性。
