Effect of aluminum sulfate and cationic polyelectrolytes on the destabilization of emulsified wastes

A.PINOTTI ; N. ZARITZKY

WASTE MANAGEMENT (ELMSFORD)

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2001 vol. 21 p. 535 - 542

0956-053X

Emulsified oil in wastewater constitutes a severe problem in the different treatment stages. Aluminum salts have been traditionally used as coagulants in wastewater treatments. Polyelectrolytes are used to coagulate and fiocculate colloidal systems. The performance of aluminum sulfate in comparison to polyelectrolytes (chitosan and polyacrylamide) as conditioning chemicals for an emulsion waste was tested, and the predominant mechanisms acting in each case were analyzed. Turbidimetry, jar test, colloidal titration and microscopy were used to test emulsion destabilization. Both charge neutralization and bridg formation were identified and confirmed as mechanisms of interaction of polyelectrolytes with waste constitutents. Charge neutralization would be more important for chitosan than for polyacrylamide treatment. A coincidence between the doses necessary to reach zero colloidal charge and minimum turbidity was observed for polyelectrolytes. The time necessary to produce system clarification was larger for aluminum sulfate than for polyelectrolytes; this time was shortened for higher aluminum sulfate concentration. The pH showed a marked efl´ect on aluminum sulfate performance with the optimum at pH 6; polyelectrolyte action was practically not affected bypH. Polyelectrolyte addition produced the minimum turbidity for the same doses that zero colloidal charg; at higher doses, emulsion was restabilized and became turbid again. However, aluminum sulfate treatment did not produce emulsion restabilization.