THE COMBINED EFFECT OF INFLUENT QUALITY AND ANOXIC SELECTOR ON ACTIVATED-SLUDGE SETTLEABILITY

The influence of three different types of influent on the sludge settl eability and metabolic capacity of activated sludge was quantified dur ing process operation with and without an anoxic selector. A significa ntly higher diluted Sludge Volume Index (dSVI) and a concomitant incre ase in filament abundance was observed when the influent quality evolv ed from fresh influent over acidified to septic influent. However, thi s deterioration in function of influent quality was noticed only when no selector was present. When no sorption phase was provided, the pres ence of rapidly metabolisable short chain fatty acids negatively affec ted the sludge settleability. It is proposed that floc formers are pot entially harmed by incomplete dentrification but selectively enhanced by slowly metabolisable organic compounds.