CONTROL OF ACTIVATED SLUDGE BY MEAN CELL RESIDENCE TIME

Abstract

The activated sludge process utilizes a continuous culture of microorgan isms in which a mixed microbial popu lation (activated sludge) grows on a mixture of organic and inorganic sub strates (wastewater). In microbiologi cal terms, the activated sludge process can be classified as a continuous cul ture with cell recycle, since the resi dence time of the sludge in the system is maintained as greater than the hydraulic residence time by recircula tion of microorganisms (return sludge). The further development of the acti vated sludge process and refinement of its operation cannot be based on the empirical methods of analysis and process description that have charac terized the early development of wastewater treatment. Since the acti vated sludge process is a microbial system, it is necessary to describe its efficiency and operational character istics in rational terms that not only are meaningful from a process and operational standpoint but also are meaningful microbiologically. There are, however, some limita tions which hinder progress toward a definitive and rational description of the activated sludge process in terms