Detection and cultivation of filamentous bacteria from activated sludge

Abstract

Different applications of the activated sludge treatment process are employed globally for the biological treatment of wastewater. Since the activated sludge process was first developed, different kinds of sedimentation problems, in particular bulking sludge and foaming, have been observed and it is widely accepted that extensive, uncontrolled growth of filamentous bacteria is the main cause of these difficulties. Since the pioneering work of Eikelboom and coworkers who characterized and described seven groups of 26 morphological types of filamentous organisms several attempts have been made to develop new methods for isolation, cultivation and identification of the isolates. Improvement has also been sought in the methods for direct detection, to allow a better understanding of the complex phenomena of sludge bulking and foaming. However, although knowledge of the phylogeny of filamentous organisms has increased recently, only a few attempts have been made to achieve a better understanding of their growth characteristics. The aim of this paper is to give an overview of detection and cultivation methods with special emphasis on the comparison of classical approaches with the modern molecular biological methods, including in situ detection and identification of filamentous bacteria.