Wang Shuai, Wang Gonglei, Yan Peng, Chen Youpeng, Fang Fang, Guo Jinsong
College of Environment and Ecology, Chongqing University, Chongqing 400045, China; College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
Sci Total Environ. 2023 Jun 10;876:162786. doi: 10.1016/j.scitotenv.2023.162786. Epub 2023 Mar 11.
The forming mechanism of non-filamentous sludge bulking during aerobic granulation were investigated basing on three feeding strategies (R1 direct aeration after fast feeding, R2 anaerobic stirring after fast feeding and R3 anaerobic plug-flow slow feeding). Results showed that strong selection stress (shortening settling time) led to a sharp flocs washout and the subsequent increase of food to microorganisms (F/M) in R1 and R3 reactors, but not found in R2 due to the different strategies of feeding modes. With the increase of F/M, zeta potential and hydrophobicity of sludge surfaces significantly decreased and thus leading to an enhanced repulsive force and energy barriers for sludge aggregation. Particularly, when F/M exceeded 1.2 kgCOD/(kgMLSS·d), non-filamentous sludge bulking was ultimately triggered in R1 and R3. Further analysis showed that massive extracellular exopolysaccharide (PS) accumulated on the surfaces of non-filamentous bulking sludge due to the increased abundance of the microorganisms related to PS secretion during sludge bulking. In addition, significantly increased intracellular second messenger (c-di-GMP), a key substance regulating PS biosynthesis, was confirmed via its concentration determination as well as microbial function prediction analysis, which played a critical role in sludge bulking. Combing with the systematic detection from surface plasmon resonance system, rheometer and size-exclusion chromatography-multiangle laser light detection-refractive index system, higher molecular weight, compact conformation, higher viscosity and higher hydrophilicity was determined in sludge bulking PS relative to PS extracted from non-filamentous bulking sludge. Clearly, the changes of PS (content, structures and properties) driven by c-di-GMP are the dominant mechanism for the formation of non-filamentous sludge bulking during aerobic granulation. This work could provide theoretical support for successful start-up and application of aerobic granular sludge technology.
基于三种进料策略（R1快速进料后直接曝气、R2快速进料后厌氧搅拌和R3厌氧推流缓慢进料），研究了好氧颗粒污泥法中无丝状菌污泥膨胀的形成机制。结果表明，强烈的选择压力（缩短沉降时间）导致R1和R3反应器中絮体急剧冲刷，随后食物与微生物比（F/M）增加，但由于进料方式不同，R2中未出现这种情况。随着F/M的增加，污泥表面的ζ电位和疏水性显著降低，从而导致污泥聚集的排斥力和能量障碍增强。特别是，当F/M超过1.2 kgCOD/（kgMLSS·d）时，R1和R3中最终引发了无丝状菌污泥膨胀。进一步分析表明，由于污泥膨胀期间与胞外多糖（PS）分泌相关的微生物丰度增加，大量胞外多糖在无丝状菌膨胀污泥表面积累。此外，通过其浓度测定以及微生物功能预测分析证实，细胞内第二信使（环二鸟苷酸，c-di-GMP）显著增加，其在污泥膨胀中起关键作用。结合表面等离子体共振系统、流变仪和尺寸排阻色谱-多角度激光光散射-折射率系统的系统检测，相对于从无丝状菌膨胀污泥中提取的PS，污泥膨胀PS具有更高的分子量、紧密的构象、更高的粘度和更高的亲水性。显然，由c-di-GMP驱动的PS（含量、结构和性质）变化是好氧颗粒污泥法中无丝状菌污泥膨胀形成的主要机制。这项工作可为好氧颗粒污泥技术的成功启动和应用提供理论支持。
