Yuan Chunyan, Sun Feiyun, Zhang Jianjun, Feng Liang, Tu Honghua, Li Ang
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China; Harbin Institute of Technology (Shenzhen), Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen, 518055, People's Republic of China.
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China; Harbin Institute of Technology (Shenzhen), Shenzhen Key Laboratory of Water Resource Utilization and Environmental Pollution Control, Shenzhen, 518055, People's Republic of China.
Chemosphere. 2023 Jan;311(Pt 2):137146. doi: 10.1016/j.chemosphere.2022.137146. Epub 2022 Nov 5.
Completely loss of granular structural stability and reliable start-up of aerobic granular sludge (AGS) system are considered as the biggest challenges for its engineering application under seasonal temperature variation, especially extremely low temperatures. In this study, two identical sequencing batch reactors (SBR) were successfully start-up at 10 °C (R1) and 25 °C (R2), respectively, and then operated under a strategy of stepwise change of temperatures to investigate the stability of the granular sludge by examining its microbial characteristics, bis (3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), extracellular polymeric substance (EPS) and sludge physiochemical properties. The results showed that AGS formed under the low temperature preferentially secrete EPS and c-di-GMP for stable granulation and improvement of its resistance to temperature changes. Meanwhile, R1 successfully obtained aerobic granulation with high biomass concentration and superior settleability, as well as high pollutant removal performance. In comparison, R2 took a longer time for granulation and was subjected to serious disintegration of AGS. The matrix structure partially formed by filamentous bacteria during the start-up stage in R1 was one of major reasons for its own superiority beyond R2 in granulation. Slow-growing organisms such as autotrophic nitrifying and Anammox bacteria, phosphorus accumulation organisms, EPS-producing genera, and c-di-GMP pathway-dependent genera, were exclusively enriched in the R1 and resulted in higher pollutants removal efficiencies and stable structure, whereas Sphaerotilus dominated in R2 that related closely with its unstable performance. Therefore, the strategy based on the stepwise change of temperatures from extremely low temperatures may be one feasible way for the sustainable application of AGS system, which is of significance to address the challenging problems of AGS applications.
颗粒结构稳定性的完全丧失以及好氧颗粒污泥（AGS）系统的可靠启动被认为是其在季节性温度变化尤其是极低温度下进行工程应用面临的最大挑战。在本研究中，两个相同的序批式反应器（SBR）分别在10℃（R1）和25℃（R2）成功启动，然后采用温度逐步变化策略运行，通过检测其微生物特性、双（3'-5'）-环二鸟苷单磷酸（c-di-GMP）、胞外聚合物（EPS）和污泥理化性质来研究颗粒污泥的稳定性。结果表明，低温下形成的AGS优先分泌EPS和c-di-GMP以实现稳定造粒并提高其对温度变化的抗性。同时，R1成功获得了具有高生物量浓度、优异沉降性能以及高污染物去除性能的好氧颗粒污泥。相比之下，R2造粒时间更长且AGS发生了严重解体。R1在启动阶段由丝状菌部分形成的基质结构是其在造粒方面优于R2的主要原因之一。自养硝化菌和厌氧氨氧化菌、聚磷菌、EPS产生菌属以及依赖c-di-GMP途径的菌属等生长缓慢的微生物仅在R1中富集，从而导致更高的污染物去除效率和稳定的结构，而R2中球衣菌属占主导，这与其不稳定的性能密切相关。因此，基于从极低温度开始逐步改变温度的策略可能是AGS系统可持续应用的一种可行方法，这对于解决AGS应用中的挑战性问题具有重要意义。
