Observations on the formation of wastewater zoogloeae

Abstract

Finger-like bacterial zoogloea formation was observed microscopically in wet mount preparations of activated sludge flocs. Elongated zoogloeae were shown by time lapse cinephotomicrography to emerge from flocs as a result of the unidirectional movement and multiplication of bacteria which synthesized an exocellular gelatinous substance. Seventy per cent of the finger-like zoogloeae measured extended at a rate of between 5.1 and 15.0 μm h −1. Certain bacteria moved freely within zoogloeae and the mean generation time of cells in three zooglocae ranged from 1.5 to 1.6 h. The development of finger-like zoogloeae may have been stimulated by an aerotactic response by the etiologic bacteria. The gelatinous nature of the zoogloeal matrix is evidenced by the slow movement of bacteria in the colony.