Chemical Treatment of Food Emulsion Wastes

PINOTTI, A; BEVILACQUA, A; ZARITZKY, N

Puebla, México

Congreso; Eigth International Congress on Engineering and Food; 2000

Food industries contribute significantly to water streams pollution. Besides, emulsified oil in wastewater must be removed to prevent fouling in process equipment, to reduce interference with subsequent water-treatment units, and to comply with water-discharge requirements. Aluminum salts have been traditionally used as coagulants in wastewater treatments; at alkaline pH, hydrolysis is produced until aluminum hydroxide precipitates. Polyelectrolytes, with high-density charge, are also used to coagulate and flocculate colloidal systems. The objectives of the present work were: a) to analyze the performance of aluminum sulfate in comparison to polyelectrolytes (chitosan and cationic polyacrylamide) as conditioning chemicals for emulsion systems and b) to determine the predominant mechanisms acting in each case. Methods used were: turbidimetry, jar test, colloidal titration and microscopic observation. Both charge neutralization and bridge formation were relevant mechanisms for polyelectrolytes. Charge neutralization was more important for chitosan than for polyacrylamide treatment and it could be attributed to the instantaneous action of the coagulant and to the coincidence between the dose to reach zero colloidal charge and minimum turbidity. In aluminum sulfate treatment, the presence of soluble compounds previous to the formation of aluminum hydroxide precipitate, lead to a longer time for system clarification. The optimum pH to destabilize the emulsion with aluminum sulfate was approximately 6; non-significant effect of pH was found with chitosan and polyacrylamide treatments.