ROLE OF EXOCELLULAR POLYMER IN THE DESIGN OF ACTIVATED-SLUDGE

This research is aimed at understanding the reactor-settler interaction. The reactor operating conditions affect the sludge-settling properties due to (a) production of exocellular polymer that serves as a flocculant in the settler and (b) population shift from flocculating bacteria to filamentous microorganisms that do not settle. A structured kinetic model that accounts for stored substrate and production of polymers, biomass, and inerts was constructed and applied to various open and closed reactor configurations. In a batch reactor the polymer is produced during endogenous respiration. The model describes well the observed temporal variation in substrate, biomass, and polymer concentration. The study confirmed the role of the polymer in the sedimentation process. Under some conditions, however, a slow population shift to filamentous growth becomes the dominant factor.