To determine the size distribution of the particles constituting
the sludge samples, a low-angle laser scattering method (laser
granulometer) was employed. The equipment used was manufactured
by CILAS, model 1064, which can cover particle sizes from
0.04 to 500 mm. Using ultrasound, the samples were dispersed with
a solution containing 0.05% sodium hexametaphosphate. For other
wastes, the Brazilian standard NBR 7181 (ABNT, 1984a) was used.
The plasticity index (PI) and Atterberg limits were evaluated
according to the Brazilian standards NBR 6459 (ABNT, 1984b) and
NBR 7180 (ABNT, 1984c).