DETERMINING GROWTH RATE, YIELD AND MAINTENANCE COEFFICIENT OF FILAMENTS AND FLOC FORMERS USING SUBSTRATE UPTAKE TESTS AND METABOLIC MODELING

The competition between filaments and floc formers in activated sludge has been described previously using kinetic selection. However, recent studies have suggested that storage phenomena may be an important factor in microbial selection, since the dynamic nature of substrate flows into wastewater treatment plants elicit transient responses from microorganisms. Respirometry used for kinetic parameters measurement should thus be reevaluated by considering storage in the cells, and a more reliable method should be developed to include bacterial storage to determine growth and metabolism of filaments and floc formers. Previous researchers performed substrate uptake tests combined with metabolic modeling to investigate the stoichiometry and kinetics of PHB (poly-β-hydroxybutyrate) and glycogen metabolism in pure and mixed cultures under dynamic substrate supply. In this study, we applied this technique to bulking and non-bulking activated sludges developed in lab scale reactors, for determining the growth rates, yields and maintenance coefficients of filaments and floc formers under feast and famine conditions.