Colour, turbidity and COD removal from old landfill leachate by coagulation-flocculation treatment

Abstract

The application of different coagulants and flocculants to leachate from an old landfill to determine the optimum conditions for removal of organic matter, colour and turbidity is studied. Ferric chloride, aluminium sulphate, aluminium polychloride (PAX) and polyacrylamide polyelectrolytes were tested. Higher pollutant removals (73% COD, 98% colour and 100% turbidity) were obtained using ferric chloride at pH 5.0—5.5 and for a dosage of 0.6 g Fe l— 1. The volume of sludge generated after centrifugation represents about 4.0—4.6% when ferric chloride or aluminium sulphate is used, and 10% when employing aluminium polychloride. When flocculants were also added, the results obtained were similar to those found when adding only coagulants, although a considerable increase in the settling rate was obtained.