The combined effect of influent quality and anoxic selector on activated sludge settleability

Abstract

Abstract The influence of three different types of influent on the sludge settleability. and metabolic capacity of activated sludge was quantified during process operation with and without an anoxic selector. A significantly higher diluted Sludge Volume Index (dSVI) and a concomitant increase in filament abundance was observed when the influent quality evolved from fresh influent over acidified to septic influent. However, this deterioration in function of influent quality was noticed only when no selector was present. When no sorption phase was provided, the presence of rapidly metabolisable short chain fatty acids negatively affected the sludge settleability. It is proposed that floc formers are potentially harmed by incomplete denitriflcation but selectively enhanced by slowly metabolisable organic compounds.