调理污泥在剪切测试过程中的絮体与聚集体之间的转化研究

Study on transformation between flocs and aggregates in conditioned anaerobic digested sludge(ADS) suspensions during a shear test

通过分析Floccky流变测试过程中不同持续剪切时间下调理污泥絮体的流变、几何和物理特征的变化,探讨了上述过程中絮体与聚集体之间的转化。结果表明,在zetag7557阳离子有机高分子絮凝剂的最佳调理投药量下,调理污泥体系的弹性网络结构的强度和耐剪切力达到最大。当絮凝剂投加到污泥悬浊体系中,大尺寸的聚集体立即出现,而且在一定范围内,随着持续剪切时间的延长,这些聚集体继续生长,此后,随着持续剪切进行,这些聚集体逐渐变成小甚至成为越来越小的絮体。在上述过程中,Floccky流变曲线上的扭矩值也呈现类似的变化趋势;弹性网络结构强度的极值出现在形成大尺寸聚集体的调理污泥体系中,但形成最大的聚集体或平均直径的调理污泥体系并不能保证弹性网络结构强度达到极值,而且调理污泥絮体分形维数的极值与Floccky流变曲线上特征峰的极值并不重合。此外,残余在悬浊体系中的zet-ag7557絮凝剂可以中和部分因调理污泥絮体剪切破碎后新出现的表面负电荷。

This study presented the variations in rheological,geometric and physical characteristics of conditioned anaerobic digested sludge（ADS） to analyze the transformation between flocs and aggregates during a rotational test with a Floccky rheometer.The results revealed that both elastic network strength and resistance to shear reached their maximum values at the optimum dosage of polymer zetag7557 on the basis of the area under torque-time rheograms of ADS.Large aggregates were observed as soon as the optimum polymer dosage was injected into the ADS suspensions,and they continued to grow as the shear duration was prolonged.Afterwards,these aggregates broke into smaller ones or were directly transformed into smaller and smaller flocs with the extension of imposed shear.During the above process,the corresponding torque values in the rheogram also showed similar behavior to the variations of conditioned ADS biosolids.The strongest elastic network formed in conditioned ADS suspensions in which large aggregates were generated,while the ADS suspension with the largest single aggregate or the highest average size of aggregates/flocs did not assure the strongest elastic network.The climax of fractal dimensions for conditioned ADS flocs were not coincident with that of the peak height in the rheograms for these ADS suspensions.In addition,residual polymers after absorption onto the surface of ADS biosolids could neutralize some of the negative surface in these biosolids exposed by shear application in the Floccky test.