Study On The Effects Of Flocculation-conditioning On The Physico-chemical And Rheological Characteristics Of Municipal Sludge

Jar test, transient and dynamic rheological was employed to determine the change in the physicalchemical properties, microstructure and rheological properties of raw and conditioned activated sludge(AS) and anaerobic digested sludge(ADS).The results showed that the optimum CZ-8698dose range of AS and ADS was observed when CST(Capillary Suction Time)、SRF(Specific Resistance to Filtration) or the supernatant viscosity in minimum values, and the corresponding CZ-8698dosage were1.43～7.13g·kg-1,9.36～12.48g·kg-1, both the zeta potential and surface charge density of colloids in AS and ADS centrifugal supernatant changed into positive values from negative, and AS flocs showed the most irregular boundary or surface and much compact structure, and the strength of these flocs gradually tended to keep constant at the conditioner doses higher than this range.Four rheological modes were used to determine the rheograms, flow curves, and parameters of raw and conditioned AS/ADS at different total suspended solid (TSS) contents. The modes were controlled shear rate (CSR), controlled shear stress (CSS), strain amplitude sweep (SAS), and frequency sweep (FS). The results showed that at the optimum CZ-8698polymer dose, the conditioned AS presented lower levels of thixotropic (shear thinning) behavior than the raw AS at most TSS contents. The relationships of the rheological parameters with the TSS content of raw and conditioned sludge, follow both the exponential and power laws. Such parameters include the hysteresis loop areas of typical rheograms, limiting viscosity, yield stress, cohesion energy of the sludge network, storage modulus, critical strain and so on. In the SAS mode, a gel-like structure was observed in both raw and conditioned sludge systems. In the FS mode, the steady structure conversion from gel-like to sol-like did not appear at all of the tested TSS contents. A positively sloped straight regression line of the double-logarithmic plots of the critical strain versus TSS content indicates a weakly linked floc/aggregate behavior of the raw and conditioned sludge, while the corresponding mass fractal dimension can be determined from above slope values. The mass fractal dimensions of raw and conditioned AS flocs/aggregates were2.38and2.09(derived from double-logarithm plots of limiting viscosity-TSS content), as well as2.70and2.53(from double-logarithm plots of storage modulus-TSS content), respectively. The AS flocs showed the worse irregular boundary or surface and less compact structure,while the mass fractal dimensions of Conditioned AS flocs much lower than raw AS. The mass fractal dimensions of raw and conditioned ADS can not be determined. The rheological tests indicated that both polymer conditioning and increased TSS content led to improved elastic behavior, cohesion energy, and yield stress of the AS network. These results provide important information on the filterability and dewaterability of AS.