EFFECT OF HIGH SUBSTRATE CONCENTRATION AND CELL FEEDBACK ON KINETIC BEHAVIOR OF HETEROGENEOUS POPULATIONS IN COMPLETELY MIXED SYSTEMS

Growth kinetics of heterogeneous populations of sewage origin were studied in completely mixed reactors of the once‐through type at a high concentration of incoming substrate, 3000 mg/l glucose, and in systems employing cell feedback or sludge recycle at an incoming substrate concentration of 1000 mg/1 glucose. The recycle flow rate employed was 25% of the incoming feed flow, and the concentration of cells in the recycle was maintained as closely as possible at 150% of the cell concentration in the reactor. Studies were made at various dilution rates. Throughout these studies, batch experiments using cells grown at the various dilution rates were made to determine ks and μm values. As in previous studios using heterogeneous populations, the relationship between specific growth rates μ and substrate concentration S was represented better by the Monod equation than by any other which was tested. The growth “constants” μm, ks, and Y were found to fall in the same general range as those determined in previous studies in once‐through systems operated at 1000 mg/l glucose. It was observed that cell recycle, even at the relatively low concentration factor employed in these studies, greatly enhanced the flocculating and settling characteristics of the cells. Copyright © 1969 John Wiley & Sons, Inc.