Effect of acclimating saccharides on the activated sludge bacterial population: composition abnormality of activated sludge acclimated to glucose

The question of whether the substitution of glucose for starch in municipal sewage as an acclimating saccharide for activated sludge (AS) in the laboratory is valid was investigated using activated sludges acclimated to glucose (G-AS) and dextrin (D-AS), since the bacteria responsible for starch (dextrin) removal in D-AS are verified to take up maltose instead of glucose during dextrin removal. In G-AS, polysaccharides are the major reserve materials, and large amounts of residual organic materials (ROM) are excreted from the AS. In contrast, in D-AS, about half of the reserve materials are low molecular weight saccharides, and no appreciable amount of ROM was detected. It is considered that most bacteria responsible for the removal of dextrin and glucose are Gram-negative and Gram-positive, respectively, based on the results of the chemical composition of AS and the type of reserve saccharide. As a result, in laboratory-scale AS processes, maltose (disaccharide) or dextrin (polysaccharide), instead of glucose (monosaccharide), should be used as a substitute for starch.