MODEL FOR CARBON METABOLISM IN BIOLOGICAL PHOSPHORUS REMOVAL PROCESSES BASED ON IN-VIVO C-13-NMR LABELING EXPERIMENTS

In vivo C-13-NMR and P-31-NMR techniques were applied to study phospho rus and carbon metabolism in activated sludge during both the anaerobi c and the aerobic stages. By supplying a C-13 label on the methyl grou p of acetate at the beginning of the anaerobic stage, the fate of the label through the subsequent aerobic/anaerobic stages was traced in vi vo, it was possible to follow the Aux of label from acetate to hydroxy butyrate/hydroxyvalerate co-polymer in the first anaerobic stage, then to monitor the conversion of these units into glycogen in a subsequen t aerobic stage, and afterwards, by submitting the same sludge to a se cond anaerobic stage, to observe the flux of labelled carbon from glyc ogen to the hydroxyvalerate and hydroxybutyrate units. The uptake/rele ase of inorganic phosphate and the extracellular pH were monitored by P-31-NMR in the same experiments. The data provide an unequivocal demo nstration of the involvement of glycogen in the biological phosphorus removal process. On the basis of these C-13 labelling data, a biochemi cal model for the synthesis of polyhydroxyalkanoates from acetate and glycogen was elaborated in which the tricarboxylic acid cycle is propo sed as an additional source of reduction equivalents. According to thi s study, from 1 C-mol acetate, 1.48 C-mol P(HB/HV) are synthesized and 0.70 C-mol glycogen are degraded anaerobically, while 0.16 P-moi phos phate is released. In the aerobic stage, 1 C-mol of P(HB/HV) is conver ted to 0.44 C-mol glycogen. Copyright (C) 1996 Published by Elsevier S cience Ltd