Enrichment and characterization of a psychrophilic 'Candidatus Accumulibacter phosphatis' culture

Enhanced Biological phosphorous removal (EBPR) processes, often operated at low temperatures, are utilised world-wide, but currently little is known regarding enrichment cultures and the characteristics of active organisms ("Candidatus Accumulibacter phosphatis" (Accumulibacter)) under psychrophilic conditions. This study assesses the long-term performance, metabolic activity, microbial community characteristics and sludge morphology in an EBPR community enriched from activated sludge at 10 degrees C. Long solid retention times (SRT) and low temperatures resulted in the dominance of Accumulibacter type II over type I. Despite changes in the microbial community, P-removal efficiencies did not show obvious differences and although no specific measures were implemented, the enriched Accumulibacter-PAO culture formed stable dense granules. A high level of Alginate-like exopolysaccharides (ALE) were observed, with a large number of Guluronic acid-Guluronic acid (GG) blocks derived from the biomass at 10 degrees C. This characteristic favors sludge granulation, increasing the mechanical strength of granules formed, which encourages solid-liquid separation and consequently, contributes to the stable operation of EBPR systems. (C) 2017 Elsevier Ltd. All rights reserved.