THE ROLE OF IONIC SURFACTANTS IN COMPRESSION DEWATERING OF ALUM SLUDGE

This work has experimentally investigated the characteristics of filtr ation followed by consolidation dewatering of an alum sludge, with esp ecial attention to the effects of adding ionic surfactants (SDS or CTA B), The filtration and consolidation stages at a pressure of 3000 psi were discussed separately, The efficiency of filtration is enhanced in the presence of surfactant molecules; however, the cationic surfactan t (CTAB) raises the consolidation rate while the anionic surfactant (S DS) retards it, A newly proposed rheological model has been employed f or interpreting the consolidation data. CTAB would not alter markedly the moisture distribution in the sludge, but SDS does increase markedl y the amount of the tightly bound moisture by diminishing the portion occupied by pore water. The possible role of surfactants in the sludge flocs is considered. Both surfactants can be used as conditioning aid s during the filtration stage. However, the applications of SDS to the consolidation stage are not encouraged. (C) 1998 Academic Press.