Activated sludge viscosity has a major impact on oxygen transfer, mass transport, and consequently influences the system performance of Membrane BioReactor (MBR) as well as the hydrodynamic regime. The experiments were carried out with a pilot airlift MBR system for domestic wastewater treatment under ambient conditions. The study investigated the rheological characteristics of sludge in the MBR under typical operating ranges of temperature (5 to 35 o C), MLSS concentration (0 to 18.7 g/L) and over a wide range of shear rate (1 to 1000 s-1), and determined the appropriate mathematical model to describe the rheology of the sludge. The sludge samples showed a shear-thinning rheological behavior, and demonstrated both static and dynamic yield stresses, a phenomenon that has not been reported yet in the literatures. The relationships between viscosity, MLSS, temperature and shear rate were obtained statistically. Furthermore, the influences of the sludge viscosity on membrane fouling and sludge settling property were discussed. A summary of the regression results for shear rate above 25 s-1 indicated that the Casson equation provides the best model for the experimental data followed by the Herschel-Bulkley equation. The Bingham equation could be suitable under low MLSS concentrations (MLSS<10 g/L).
|Title of host publication||Membrane science and technology conference of Visegrád countries|
|Subtitle of host publication||Siófok, Hungary|
|State||Published - 1 Sep 2007|