Effect of sludge age on heavy metal biosorption by selector activated sludge

The influence of sludge age on the metal biosorption characteristics of an aerobic selector-activated sludge was investigated. Two bench-scale aerobic-activated sludge systems were operated at sludge ages of 5 days and 15 days for studying biosorption of Cu and Cr(VI). In-vitro batch experiments were performed to compare biosorption characteristics of the sludge samples harvested from the bench-scale systems. Adsorption capacity (k) of the sludge for both of the metals was found to decrease with increasing sludge age from 5 days to 15 days However, percent removals of the metals were variable in relation to sludge age. Although Cr(VI) removal increased from 33% to 68%, Cu removal exhibited a slight decrease from 81% to 74% with increasing sludge age