• 关键词：活性污泥  理化性质  脱水性能  剪切强度  剪切稳定性

• 基金项目：国家自然科学基金资助项目（No.51078035，21177010）；高等学校博士学科点专项科研基金（No.20100014110004）；人力资源和社会保障部留学回国人员科技活动择优资助重点项目

• 张越
• 北京林业大学环境科学与工程学院, 北京市水体污染源控制技术重点实验室, 北京 100083

• 王毅力
• 北京林业大学环境科学与工程学院, 北京市水体污染源控制技术重点实验室, 北京 100083

• 摘要：通过实验室模拟，研究了原始活性污泥和最佳投药量下调理污泥的毛细管吸水时间、粒度、分形维数、Zeta电位和上清液SS值等参数随剪切强度与时间的变化规律，确定了污泥的剪切敏感性和强度因子及粒径、强度等参数与速度梯度（G）值之间的关系.结果表明，剪切导致原始污泥和调理污泥的脱水性能变差，相应的临界剪切强度分别为700 r·min^-1（G=554.6 s^-1）和400 r·min^-1（G=239.5 s^-1），并暴露出更多带负电荷的新鲜表面.原始污泥的质量分形维数受剪切作用影响不大，其粒径在一定范围内随剪切强度的增加而减小，而调理污泥絮体的质量分形维数却随之上升，粒度随之降低.原始污泥与调理污泥絮体的K_SS值分别为4.73×10^-2、8.33×10^-2，稳定絮体粒径常数γ值分别为4.99×10^-2、35.19×10^-2，且前者的强度因子较高，它们均表明原始污泥的剪切稳定性更好.剥离是原始污泥剪切破碎的主要机制，而调理污泥在临界剪切强度以上呈现越来越明显的剪切分裂机制.此外，污泥粒径、强度均与G值呈现较好的指数关系.

• Abstract：In this study, shear tests were conducted to obtain the variations of capillary suction time (CST), floc size, fractal dimension, zeta potential and suspending solid (SS) in supernatant of raw and conditioned activated sludge (AS) with shear strength and time. The parameters of shear sensibility, strength factor and the relationships between floc size or strength and average velocity gradient (G) were determined. The results showed that shear could deteriorate the dewaterability of both raw and conditioned AS, and cause the exposure of more fresh surface with negative charge. For the raw and conditioned AS samples, the corresponding critical shear strength was 700 r·min^-1 (G=554.6 s^-1) and 400 r·min^-1 (G=239.5 s^-1), respectively. With the increase of the shear strength imposed on the raw AS, the fractal dimensions roughly kept constant and the floc sizes decreased slightly. For the conditioned AS, the increase of shear strength led to the rising of the floc fractal dimensions and the decrease of the floc size. Furthermore, in comparison with the conditioned AS (shear sensitivity (K_SS)=8.33×10^-2, floc size exponent (γ)=35.19×10^-2), the raw AS showed a greater shear stability on the basis of its lower K_SS of 4.73×10^-2, lower γ of 4.99×10^-2 and higher strength factor value. Under the shear conditions, the surface erosion was the main mechanism for the raw AS, while the fragmentation mechanism became more and more obvious for the conditioned AS beyond the critical shear strength. In addition, both the floc size and strength presented good exponent correlations with G.

• Key words：activated sludge  physicochemical characteristics  dewaterability  shear strength  shear stability

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