Dear Ghoewyiah, Activated ...

Dear Ghoewyiah,

Activated sludge flow rheology is a very complicated phenomenon. Studies related to activated sludge tend to classify sludge as non-Newtonian fluid. Until now, several theories have been built to describe the complex behavior of activated sludge with varying degrees of success. sludge with solids concentrations above about 2% exhibit non-Newtonian behavior, i.e., the sludge apparent viscosity changes with the shear rate (flow velocity).Sludge rheological properties play a fundamental role in determining its performance in pipes, tanks or reactors. However, the relative information on high-solids sludge is very rareincrease of solid particles concentration in the liquid leads to arising from the strength of the system, which means that below certain value of shear stress the system will behave like a solid, but above this value will flow with variable viscosity depending on the shear velocity. The variability of viscosity is the result of structure

changes proceeding in the sludge during the flow. Thickening of sludge increases its viscosity and causes more difficulties in the pump and hydraulic transport as the resultThe rheological characteristics of digested sludge are severely temperature dependent. An effect of temperature on rheological properties of digested sludge is partially irreversibleThe rheology of digested sludge affects the flow hydrodynamics, dewaterability, and the polymer consumption in wastewater treatment plants. The rheological characteristics of digested sludge are highly dependent on changes in total solid concentration, temperature, and polymer doseFor the high-solids sludge with TS 6%, 8%, 10% and 12%, their viscosities increased by 5.0, 9.1, 25.7and 24.9 times, respectively, when sludge organic content increased from 28% to 53%, and decreased by 36.5%, 49.5%, 54.0% and 65.4%, respectively, when sludge temperature rose from 9 ºC to 55 ºC. 

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