Variable morphology in certain filamentous bacteria and the implications of this for theories of activated sludge bulking

Abstract

Many activated sludges are subjected to a rapid proliferation of filamentous bacteria leading to a bulking sludge. This phenomenon often occurs in 24 hr or less and these same sludges appear able to eliminate the filamentous bacteria in an equally short time period. Two causative filamentous bacteria have been characterised and grown under a range of feed‐fast regimes. The imposition of a fasting phase caused morphological changes in the filaments with an ultimate breakdown to individual cells. This change was fully reversible. The significance of this observation for current theories of sludge bulking, is discussed.