Nocardia amarae strains were isolated from foaming activated sludge, and their growth was studied in axenic culture on a defined substrate. The method of chemostat culture withdrawal (surface overflow or subsurface withdrawal) determined whether a dispersed or clumped growth form was obtained. Steady-state growth kinetic coefficients for acetate and oxygen suggested that Nocardia amarae would be a poor competitor in completely mixed activated sludge. Batch studies showed that Nocardia amarae acetate uptake rates and storage capacities increased with decreasing growth rate. Nocardia amarae denitrified slowly and only to nitrite. The organism did not take up acetate under either anoxic or anaerobic conditions. The results suggest possible reasons for severe foaming incidents in activated sludge and methods for controlling Nocardia amarae growth using selectors.
Research Journal of the Water Pollution Control Federation,
Vol. 63, no. 1 (Jan 1990), pp. 44-50