When the desiccation of sludge is carried out mechanically, lime can be used with different objectives in the following phases:
A) BEFORE FILTRATION. The conditioning is carried out by adding lime grout to the liquid mud producing a coagulation effect of the colloidal particles, an increase in the size and weight of the “flakes”, as well as the dry matter content. At the same time, it improves the filtration of the mud and its sanitization (blocking of fermentations and elimination of pathogenic organisms due to an increase in pH).
B) AFTER FILTRATION. Stabilization and drying is achieved by adding quicklime to the mud. In this way, an increase in dry matter content is obtained. The mixture of water with lime produces an increase in temperature and the union of a molecule of water with a molecule of calcium oxide causes the drying of the mud. The heat of hydration of 1 kg of lime can heat 2 liters of water from 0º C to its boiling point, 100ºC. A sanitization of the mud also occurs due to an increase in pH and temperature.
