The concentrations of proteins and polysaccharides were used as surrogate indicators to further assess the reduction of the excess sludge (Fig. 2). During the 60-day operation, the proteins and polysaccharides concentration in the extracted EPSs from the A2O-B process was substantially decreased (decreasing rate of proteins = 29%, decreasing rate of polysaccharides = 23%). However, a slight reduction in the concentrations of proteins and polysaccharides was found for the extractedEPSs from the activated sludge of the A2O-C process (decreasing rate of proteins = 6.5%; decreasing rate of polysaccharides = 8%).