Abstract
The flow behavior of excess activated sludge containing highly concentrated organic solid, and showing an extremely thixotropic nature, was investigated.
An experimental method for measuring the flow characteristics of the sludge under the condition of the same structure was proposed. By applying this method the relationship between shear rate and shear stress of a samestructure sludge was obtained, and it was found that the relationship was very similar to that of a plastic fluid. The relationship was named the sludge structure curve (SSC). SSC was degenerated into one curve by using a yield stress which was characteristic of each structure. This curve was named the sludge characteristic curve (SCC), because SCC was uniquely determined by the concentrations of solid and sludge conditioning agent, independently of sludge structure and temperature.
