DEWATERING OF ACTIVATED-SLUDGE BY AN OXIDATIVE TREATMENT

Different activated sludges from pulp and paper mills were treated wit h hydrogen peroxide in the presence of ferrous sulphate under differen t reaction conditions in order to improve the dewatering characteristi cs of the sludges. The efficiency of the treatment was evaluated on th e basis of the specific filtration resistance. Although sludges from d ifferent mills varied considerably with respect to their chemical comp osition and dewatering properties, the specific resistance values of a ll the sludges could be decreased using rather mild conditions. The fi lterabilities of the sludges were dependent on reaction temperature, h ydrogen peroxide concentration and the reaction time used in the oxida tive treatment. Depending on the type of sludge, hydrogen peroxide con centrations of 15 to 30 % mmoles/l sludge were sufficient to decrease the filtration values to a low level at 70-degrees-C using a reaction time of 1-2 hours at pH 3.