QUANTIFICATION OF THE KINETIC DIFFERENCES BETWEEN COMMUNITIES ISOLATED FROM COMPLETELY MIXED ACTIVATED-SLUDGE SYSTEMS OPERATED WITH OR WITHOUT A SELECTOR USING A NOVEL RESPIROMETRIC METHOD

This study quantified the kinetic differences in microbial communities isolated from completely mixed activated sludge (CMAS) systems that w ere operated either with or without an aerobic selector preceding the main reactor. A new respirometric method was employed that allowed the determination of biodegradation kinetics from single oxygen consumpti on curves, thereby minimizing physiological changes to the examined co mmunities during the assay. Results indicated that increased values fo r K-s and mu(max) for acetate, phenol, and 4-chlorophenol degradation were measured in the CMAS system operated with a selector. The biomass yields on acetate, phenol, and 4-chlorophenol were very similar in bo th systems. These findings indicate that the operation of CMAS systems with aerobic selectors may result in the selection for degrading popu lations with higher K-s and mu(max) values for both biogenic and xenob iotic organic compounds, and that substrate storage in the selector on ly partially contributes to increased substrate removal rates.