Possible Adverse Effect of Protozoa on Effluent Purification Systems

Abstract

EFFLUENT purifications systems based on the “activated sludge system” contain a naturally occurring population of microorganisms which can be represented as a continuous-flow culture of either chemostat or plug-flow type. In the ideal chemostat type the culture is completely mixed, whereas in the ideal plug-flow type it flows through the vessel without mixing. Both types of system are used, but the choice seems arbitrary although recent theory suggests that the chemostat system is better¹. In view of the large capital sums now being invested in sewage disposal, the arbitrary design of the activated sludge process² calls for urgent investigation. A case in point is the effect of protozoa on the process.