KINETICS OF POLYMERIC SUBSTRATE (DEXTRIN OR PEPTONE) REMOVAL BY ACTIVATED-SLUDGE - HYDROLYSIS OF POLYMERS TO MONOMERS IS THE RATE-DETERMINING STEP

Most of the organic compounds in primary effluent are polymers such as proteins and polysaccharides. However the bacteria present in activat ed sludge (AS) can only directly take up monomers such as amino acids and glucose which are produced from polymers by hydrolysis. Therefore, it is assumed that the hydrolysis of polymers to monomers by the bact eria is the rate-determining step in polymer removal. In this study, A S was acclimated to dextrin or peptone, and polymers (dextrin or pepto ne) and monomers (glucose or a mixture of free amino acids) were used as substrates for kinetic tests. The removal of monomers and polymers by the AS followed zero-and pseudo first-order reaction kinetics, resp ectively. The removal rate of monomers was higher than that of polymer s, and the oxygen uptake rate of the AS during monomer removal was hig her than that during polymer removal. One of the important differences between the polymers and monomers used in this study is whether glyco sidic linkages or peptide bonds exist in the material. It was therefor e verified that the hydrolysis of polymers to monomers by AS was the r ate-determining step in polymer removal. The removal of polymers appar ently followed first-order reaction kinetics at high F/M ratios, but n th-order reaction kinetics at low F/M ratios (n>1), which are commonly used in municipal sewage treatment. (C) 1997 IAWQ. Published by Elsev ier Science Ltd.