Z. Dymaczewski et al., COAGULATION AS A STRUCTURE-FORMING SEPARATION PROCESS IN WATER AND WASTE-WATER TREATMENT, Water science and technology, 36(4), 1997, pp. 25-32
Citations number
12
Categorie Soggetti
Water Resources","Environmental Sciences","Engineering, Civil
This paper presents the results of research on coagulation sludge prop
erties in three waterworks. The investigation assumed: chemical compos
ition, specific surface of coagulation structures: their sedimentation
, gravity thickening and rheological parameters. The solid fraction of
the examined structures consisted mostly of mineral substances, espec
ially silica, aluminium and iron oxides. This composition is typical f
or most coagulation sludges formed in surface water treatment faciliti
es. It has been determined, that the main factor determining structure
s properties is chemical composition of the solid fraction, mainly alu
m and iron oxides. Their presence in the sludge causes a high specific
surface in coagulation structures, and significantly influences the r
heological properties. It has been proved that non-Newtonian propertie
s appear first in structures with the highest contents of alum and iro
n oxides, with limit concentrations of c. 1.5%. Investigations on sedi
mentation and gravitational thickening showed a high stability of coag
ulation structures vs. forces. The water amount in the investigated sl
udges during their compression was no lower than 94-98%, which means t
hat gravitational forces did not destroy these structures. The factors
stabilizing coagulation sludges are; fine dispersion of the solid pha
se and high affinity to water molecules, This is why in the range of h
ydrations lower than the compression hydration, the coagulation struct
ures are classified as quasihomogenous systems consisting of two inter
penetrating quasicontinuous media, which means; solution of liquid dis
persed to colloidal and semicolloidal particles of the solid phase. Th
ey act on each other by intermolecular forces, which are the volume fo
rces. (C) 1997 IAWQ. Published by Elsevier Science Ltd.