Selection between alcohols and volatile fatty acids as external carbon sources for EBPR

The purpose of this paper is to provide a basis for selecting alcohols (i.e. ethanol and methanol) or short-chain volatile fatty acids (VFAs) (i.e. acetate and propionate) as the external carbon sources for enhanced biological phosphorus removal (EBPR) from wastewaters in adapted or unadapted activated sludge. When ethanol is used in an unacclimated process, a period of adaptation is required by polyphosphate-accumulating organisms (PAOs). From 0 to 140 days of ethanol acclimatizing, the P release and uptake rates increased to 6.2 and 7.0 mg P-PO₄^3- g^-1 VSS h^-1, respectively. PAOs in ethanol-enriched sludge produced poly-β-hydroxyvalerate (PHV) (81.9%) as the main polyhydroxyalkanoate (PHA) and reached an effluent phosphate concentration close to zero (0.10 mg P-PO₄^3- L^-1). On the other hand, methanol was not used by PAOs in 30-day ethanol-acclimated sludge in short-term tests. If EBPR needs to be incidentally supported by substrate addition, VFAs are preferred; for long-term addition also ethanol can be considered.