Detection of filamentous bacteria in activated sludge

Abstract

Attempts were made to isolate the filamentous bacteria responsible for bulking at Goudkoppies activated sludge plant in Johannesburg, South Africa, in order to allow fluorescent antibody against these microorganisms to be produced and to facilitate and simplify their identification. Of the filaments only Nocardia could be isolated using standard techniques as the growth requirements of the other filaments present are unknown. Attempts were made to prepare a fluorescent antibody to the Nocardia isolate and to an isolate of Sphaerotilus natans (Kutzing), but success was only achieved with the latter. The antiserum reacted specifically with S. natans. Subsequently, existing microscopic techniques for the identification of filamentous bacteria occurring in activated sludge were compared with the use of the S. natans fluorescent antiserum. The bacterium was found to be abundant in only one bulking sludge sample. In five other samples, filaments of S. natans occurred but in such low numbers that only the use of the fluorescent antibody allowed their discovery and positive identification. The use of the fluorescent antiserum proved to be a rapid, simple and accurate test to determine whether S. natans was present in a bulking sludge and whether it played a significant role in the process.