THE ROLE OF DISPERSED NOCARDIOFORM FILAMENTS IN ACTIVATED SLUDGE FOAMING
Abstract:Activated sludge foaming caused by filamentous microorganisms is a major wastewater treatment plant operating problem. This paper presents the results of an investigation of the role of dispersed nocardioforms in activated sludge foaming. Dispersed nocardioforms had a greater propensity for foaming than floc-bound nocardioforms. The mode of effluent withdrawal from an aeration basin plays a major role in determining the relative proportion of dispersed and floc-bound nocardioforms in the activated sludge. Reactors with “trapping” features (sub-surface effluent withdrawal) had significantly higher dispersed nocardioform populations than reactors with “non-trapping” features (surface effluent withdrawal). High dispersed nocardioform filament concentrations were correlated with a high propensity for foaming. Cationic polymer and poly-aluminum chloride reduced foaming by flocculating dispersed nocardioforms, thereby converting them to floc-bound nocardioforms. Low non-ionic surfactant concentrations changed the relative proportions of dispersed and floc-bound nocardioforms by deflocculating floc-bound filaments and converting them to the dispersed growth form. This could act as a trigger for initiating the rapid-onset nocardioform foaming events observed at activated sludge plants.
Document Type: Research Article
Publication date: January 1, 2003
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