College of Environmental Science and Engineering, Key Laboratory for Silviculture and Conservation of the Ministry of Education and Beijing, Beijing Forestry University, Beijing 100083, China.
Water Res. 2010 Dec;44(20):6041-52. doi: 10.1016/j.watres.2010.07.068. Epub 2010 Aug 3.
Wastewater sludges are non-Newtonian fluids because their shear rates change with shear stress and no linear relationship is observed between their shear stress and shear rate. Therefore, it is necessary to condition sludges with polyelectrolytes prior to dewatering to increase in the dewaterability. Since 1978, researchers have observed that the yield strength of conditioned sludge increased with the addition of polymer up to the optimum dose. Then sludge rheogram was used as a control parameter to optimize the addition of polymers, and the peak height in the shear stress vs. shear rate curve was an indication of sludge conditionablity, where the optimum polymer conditioning corresponding to the highest peak was obtained. However, few studies have addressed the effects of distinct conditioning factors on the appearance of peaks in such rheograms. In this study, the impact of factors such as high speed mixing and polymer dosing rates on the geometric and rheological characteristics of conditioned anaerobic digested sludge (ADS) with the polymer zetag7557 were investigated through the jar test method. The results showed that both the high speed mixing time and polymer dosing time had important effects on the emergence of the initial peak in test curves obtained using the Haake RV20 and Flokky rheometers for evaluation of conditioned ADS. A high speed mixing time within 60 s or a polymer dosing time of 5 s was sufficient for observation of the initial peak in flow curves, and both peak height and area decreased as the high speed mixing times were prolonged in most cases in this study. As same as the high speed mixing time, the extension of zetag7557 dosing time can also lead to the gradual decrease in the initial peak size of test curves, and form small aggregates with a decrease in two-dimensional fractal dimensions (D(2)). Although the initial peak in the test curves was observed when high speed mixing intensities increased up to 300 rpm, there were several differences in the peak height and area observed on the Haake RV20 test rheograms and Floccky test curves. In addition, a high speed mixing intensity of 300 rpm was found to lead to the formation of smaller and less compact aggregates than other mixing intensities. All of the rheological and geometric parameters were somewhat correlated with fractal dimension-D(2P) (based on regression analysis of the logarithmics of area and perimeter). However, D(2L)(based on regression analysis of the logarithmics of area and maximum diameter) did not show good correlation with any other parameters. The median diameters of the aggregates were well correlated with one-dimensional fractal dimensions (D(1)).
污水污泥是一种非牛顿流体，因为其剪切速率随剪切应力而变化，并且在剪切应力和剪切速率之间没有观察到线性关系。因此，在脱水之前，有必要用聚电解质对污泥进行调理，以提高脱水性能。自 1978 年以来，研究人员观察到，随着聚合物添加量的增加，调理后污泥的屈服强度增加，直至达到最佳剂量。然后，将污泥流变法用作控制参数来优化聚合物的添加，并且剪切应力与剪切速率曲线中的峰值高度是污泥可调理性的指示，其中获得了对应于最高峰值的最佳聚合物调理。然而，很少有研究涉及不同调理因素对这种流变法中峰出现的影响。在这项研究中，通过Jar 测试方法研究了高速混合和聚合物投加速率等因素对用聚合物 zetag7557 调理的厌氧消化污泥（ADS）的几何和流变特性的影响。结果表明，对于使用 Haake RV20 和 Flokky 流变仪评估调理 ADS 的测试曲线，高速混合时间和聚合物投加时间都会对初始峰的出现产生重要影响。在 60 s 内的高速混合时间或 5 s 的聚合物投加时间足以观察到流变法中的初始峰，并且在大多数情况下，随着高速混合时间的延长，峰高和面积都会减小。与高速混合时间一样，zetag7557 投加时间的延长也会导致测试曲线初始峰的尺寸逐渐减小，并随着二维分形维数（D(2)）的减小而形成小的聚集体。尽管当高速混合强度增加到 300 rpm 时，可以观察到测试曲线中的初始峰，但是在 Haake RV20 测试流变图和 Floccky 测试曲线上观察到的峰高和面积存在一些差异。此外，发现 300 rpm 的高速混合强度会导致形成比其他混合强度更小且更不紧凑的聚集体。所有流变学和几何参数都与分形维数-D(2P)（基于面积和周长对数的回归分析）有些相关。但是，D(2L)（基于面积和最大直径对数的回归分析）与任何其他参数都没有很好的相关性。聚集体的中值直径与一维分形维数（D(1)）很好地相关。
