[Relationship between physicochemical characteristics of activated sludge and polymer conditioning dosage]

Jar test was employed to determine the relationship between physicochemical characteristics of activated sludge (AS) and polymer conditioning dose. The evolutions of indexes representing the AS physicochemical characteristics, such as the viscosity of AS centrifugal supernatant, zeta potential and surface charge density of colloids in it, size, fractal dimensions and strength of AS flocs, with polymer doses of CZ-8698 in flocculation conditioning process were recorded and analyzed. In addition, the difference in determining the optimum dosage of AS conditioner was identified among the aforementioned indexes. The results showed that CZ-8698 doses had a great impact on the dewaterability and physicochemical characteristics of AS. The range for optimum CZ-8698 dose was 4.28-7.13 g x kg(-1) on the basis of capillary suction Time (CST) and specific resistance to filtration (SRF) test, and the corresponding values for CST and SRF were (12.62 +/- 1.39)s and 0.56 x 10(12)m x kg(-1), respectively. In this optimum range, both the zeta potential and surface charge density of colloids in AS centrifugal supernatant changed into positive values from negative ones, and AS flocs showed the most irregular boundary or surface and much compact structure, which was demonstrated by their fractal dimensions of 1.09 (one-dimensional fractal dimension, D1) and 1.51 (two-dimensional fractal dimension, D2). Although AS flocs grow up to millimeters scale with the increase of CZ-8698 doses, the strength of these flocs gradually tended to keep constant at the conditioner doses higher than 4.60 g x kg(-1). Furthermore, when conditioner dosage was much less than above optimum dosage range, the viscosity of AS centrifugal supernatant reach the minimum value (1.24 +/- 0.04) mPa x s.