The paper presents research results on rheological properties of a precipitated waterwork sludge. The water content of the sludge studied varied from 100 to 85 per cent at temperatures of 273-293 K, respectively. The sludge in question can be classified as a plastic-viscous fluid, described by the Bingham model. Some empirical relations describing the influence of the water content on τ0 and ηpl have been found. The mentioned parameters were also affected by temperature. The paper describes in detail, technical applications such as the flow of sludge in pipes, as well as the flow along the bottom of sedimentation tanks.
The paper discusses the results of experiments with ultrasound application. Ultrasound is applied to change the polyelectrolyte's structure. Presented results indicate that the ultrasonic field may be useful for sewage sludge dewatering.
This paper presents the results of research on coagulation sludge properties in three waterworks. The investigation assumed: chemical composition, specific surface of coagulation structures, their sedimentation, gravity thickening and rheological parameters. The solid fraction of the examined structures consisted mostly of mineral substances, especially silica, aluminium and iron oxides. This composition is typical for most coagulation sludges formed in surface water treatment facilities. It has been determined, that the main factor determining structures properties is chemical composition of the solid fraction, mainly alum and iron oxides. Their presence in the sludge causes a high specific surface in coagulation structures, and significantly influences the rheological properties. It has been proved that non-Newtonian properties appear first in structures with the highest contents of alum and iron oxides, with limit concentrations of c. 1.5%. Investigations on sedimentation and gravitational thickening showed a high stability of coagulation structures vs. forces. The water amount in the investigated sludges during their compression was no lower than 94-98%, which means that gravitational forces did not destroy these structures. The factors stabilizing coagulation sludges are; fine dispersion of the solid phase and high affinity to water molecules. This is why in the range of hydrations lower than the compression hydration, the coagulation structures are classified as quasihomogenous systems consisting of two interpenetrating quasicontinuous media, which means; solution of liquid dispersed to colloidal and semicolloidal particles of the solid phase. They act on each other by intermolecular forces, which are the volume forces.
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