Microbial population dynamics in enhanced biological phosphorus removing activated sludge systems

In terms of wastewater treatment, the activated sludge process is probably the most important biotechnological process at present. Although a considerable amount of work has been done on system design and process engineering, some systems designed for enhanced biological phosphorus removal (EBPR) fail, thus necessitating chemical precipitation to meet effluent standards. Studies on the microbial ecology of activated sludge to optimize the process have received much attention. Culture-dependent, fluorescent antibody and molecular techniques, as well as polyacrylamide gel electrophoresis and community-level carbon source utilization methods have contributed to a better, but yet incomplete understanding of EBPR as well as other problems, such as bulking and foaming, which are microorganism related. Hence, microbial diversity and, more importantly, the function of populations in a specific community have not been elucidated, excepting in cases where a specific function can be attributed to a specific microbial population (e.g., nitrification). Most of our current knowledge regarding the microbiology of EBPR has been descriptive. However, as the methodology for studying microbial population dynamics improve, it will lead to a fundamental understanding of EBPR, bulking, foaming, etc., which could lead to major improvements in process design and operation. Key words: enhanced biological phosphorus removal, activated sludge, population dynamics, microenvironments, physicochemical properties, metabolic processes, modeling.