Pollice A, Giordano C, Laera G, Saturno D, Mininni G
CNR IRSA, Viale F. De Blasio 5, 70123 Bari, Italy.
Environ Technol. 2006 Jul;27(7):723-32. doi: 10.1080/09593332708618690.
A rheological characterization of the sludge sampled from a complete retention membrane bioreactor was performed in order to correlate the apparent viscosity with the concentration of solids. The three most commonly adopted models were tested to select the one better fitting the experimental data. Ostwald model was choosen, and the relationship between the apparent viscosity and the shear rate was determined for mixed liquor suspended solids (MLSS) concentrations ranging between 9 and 25 g l(-1). Ostwald model parameters k and n were correlated with MLSS concentration, comparing linear, power, and exponential-power (only for k) laws in terms of R2 and Mean Root Square Error (MRSE). Both power and exponential-power functions provided good and comparable correlations for parameter k, while the linear relationship was much less accurate, especially at the highest solid concentrations. The parameter n was better modelled by a power function than by a linear one. Therefore two simulation models were proposed, both based on Ostwald's equation, where the two parameters k and n were expressed as functions of MLSS. Evaluation of energy consumption for mixing showed that the increase of solid concentration from 3 to 30 g l(-1) resulted in a limited increase in energy requirement (25-30 %). In real systems, where Reynolds numbers shift towards the turbulent regime, the increase of energy requirements for increasing solids concentration is even less pronounced. The thixotropy of membrane bioreactor sludge was also evaluated by measuring the rHa (reduced hysteresis area) and relating this parameter to the characteristics of the sludge growing within the reactor.
为了将表观粘度与固体浓度相关联，对从完全截留膜生物反应器中采集的污泥进行了流变学表征。测试了三种最常用的模型，以选择最适合实验数据的模型。选择了奥斯特瓦尔德模型，并确定了混合液悬浮固体（MLSS）浓度在9至25 g l(-1)范围内时表观粘度与剪切速率之间的关系。将奥斯特瓦尔德模型参数k和n与MLSS浓度相关联，从R2和均方根误差（MRSE）方面比较线性、幂函数和指数幂函数（仅针对k）规律。幂函数和指数幂函数对参数k都提供了良好且可比的相关性，而线性关系的准确性要低得多，尤其是在最高固体浓度时。参数n用幂函数建模比用线性函数更好。因此，提出了两个基于奥斯特瓦尔德方程的模拟模型，其中两个参数k和n表示为MLSS的函数。混合能耗评估表明，固体浓度从3 g l(-1)增加到30 g l(-1)导致能量需求仅有限增加（25 - 30%）。在实际系统中，雷诺数向湍流状态转变时，固体浓度增加导致的能量需求增加甚至更不明显。还通过测量rHa（减小的滞后面积）并将该参数与反应器内生长的污泥特性相关联，评估了膜生物反应器污泥的触变性。
