FOAMING IN ACTIVATED-SLUDGE PROCESSES - AN OPERATORS OVERVIEW

The formation of stable surface foams, which is associated with characteristic filamentous microorganisms, is a worldwide phenomenon on activated-sludge plants. In excess, it can create operating difficulties and may cause a violation of effluent consent conditions due to high concentrations of suspended solids and solids-related biochemical oxygen demand. Despite its universal occurrence, the reasons for foaming are not clearly understood, and control measures tend to be non-specific, hit-or-miss strategies. This paper presents an operator's perspective on (a) the current knowledge of foam-forming microorganisms, and (b) methods to control them.