Filamentous organism bulking in nutrient removal activated sludge systems - Paper 7: Exploratory experimental investigations

This paper describes an experimental investigation into the causes of proli feration of low F/M filaments in activated sludge system configurations whi ch expose the mixed liquor to alternating anoxic-aerobic conditions. Using laboratory-scale anoxic-aerobic systems fed defined artificial substrate or municipal sewage, a combination of conditions is identified which results in low F/M filament proliferation; i.e. exposure of sludge to alternating a noxic-aerobic conditions with slowly biodegradable COD (SBCOD) present unde r bath anoxic and aerobic conditions, with an aerobic mass fraction of 30 t o 40% of the total,and nitrite (NO2-) present at a concentration greater th an about 1.0 mgN/l when conditions change from anoxic to aerobic.