Biological treatment process is a typical ecosystem composed of bacteria, fungi, protozoa and small metazoa. However, the role of small metazoa in the purification process has been known only little compared to that protozoa in the biological treatment process. The present study, therefore, was performed to aim at elucidating the role of small metazoa on the purification in biological treatment process by examining their growth and purification characteristics. The purpose of this study was to make clear the interactions on growth between protozoa and small metazoa with mixed culture. In this study, Rotatoria such asPhilodina erythrophthalma (P), Oligochaeta such asAeolosoma hemprichi (A), Protozoa such asColpidium camphylum (C) and Bacteria such asAcinetobacter calcoaceticusIAM 1517 were used as one the case of mixed culture. Results may be summerized as follows : (1) The growth ofP. eryhrophthalmaandA. hemprichiwere decreased remarkably in case of inoculate P, A, C at the same time simultaneously. (2) Maximum number (Nmax) ofC. ramphylumat the logalistic growth phase ofP. erythrophthalmaandA. hemprichi. (3) Specific growth rate and Nmax ofC. camphylumat the stationary phase ofP. erythrophthalmaandA. hemprichi. (4) Growth abilities was enhanced in order of monoxenic culture (P system and A system), PA system, PAC system and PC or AC systems.
