厌氧折流板反应器(ABR)中成熟颗粒污泥的分形分析

Fractal analysis on mature granular sludge in an anaerobic baffled reactor (ABR)

研究了ABR反应器启动成功后成熟颗粒污泥的物理性质和不同拓扑空间下的分形维数.结果表明,在反应器启动成功后,各格室中形成了平均粒径为1.70-2.70mm、边界较为清晰的黑色颗粒污泥.它们的SVI值为25-35mL·g^-1,有效密度主要集中在1.02g·mL^-1以下,自由沉降速率主要集中在14.40-86.40m·h^-1之间.在它们的等速自由沉降的过程中,第2格室到第5格室中颗粒污泥水平方向的投影平均直径与垂直投影方向上平均直径的比值接近0.73,而第1格室的这一比值却为0.83.依据沉降速率-当量圆直径的双对数图计算出的各格室中颗粒污泥的质量分形维数Df处于2.097-2.801之间,大小顺序为第5格〉第3格〉第2格≥第1格〉第4格,表明第5格室中形成的颗粒污泥较为密实,而第4格室的密实程度最小,但密实的颗粒污泥并不一定意味着较高的平均沉降速率.此外,依据投影法计算出的ABR各格室中颗粒污泥在低维拓扑空间下的几种分形维数之间的关系与其理论公式之间的关系相符,其中二维拓扑空间的分形维数为1.69-1.84（投影面积-长轴）,大小顺序为第3格室〉第1格室〉第5格室〉第4格室〉第2格室,这些D2不等于2,即不符合Meakin的结论.一维拓扑空间下的分形维数在0.99-1.03之间,各格室之间差异不大,表明颗粒污泥的边界不规则程度小.

The physical properties and fractal dimensions within different topological spaces of the mature granular sludge in an anaerobic baffled reactor （ABR） were investigated. The results showed that black granules with distinct boundaries were found in all five compartments of the ABR. Their SVI values were between 25 mL·g^-1 and 35 mL·g^-1 and average diameters were 1.70-2.70 mm. Their test free settling rates were mainly 14.40-86.40 m·h^-1,and most had a calculated effective density of less than 1.02 g·mL^-1.During the free settling process with equal rates, the ratio between the average granule diameters in the 1st compartment from the horizontal and vertical projected views was close to 0.83, but the ratios for the sludge granules in the other compartments were close to 0.73. Moreover, their mass fractal dimensions Dr, calculated by a bilogarithmic relation between settling rates and equivalent circle diameters, were 2.097-2.801, and the Df value for granules in the 5th compartment was the highest, indicating that the most compact granules were formed. The least compact granules were observed in the 4th compartment, and the granules in the 1st and 2nd compartments showed close compactness. However, the highest average settling rate for granules was detected in the 1st compartment. In addition, the relationships among the calculated fractal dimensions in 1-D and 2-D topological spaces for these ABR granules derived from image analysis matches the theoretical relationships. The fractal dimensions in 2-D topological space for these granules based on the projected area-maximum diameter bilogarithmic relationship were 1.69-1.84, and they show an order of D2 values： in 3rd compartment〉1 st compartment 〉 5th compartment 〉 4th compartment 〉 2nd compartment. The fractal dimensions in 1-D topological space of 0.99-1.03 indicate that there is little irregularity in the boundaries of these granules and there are no distinct differences among the five compartments.