title: Physical enrichment of polyphosphate-accumulating organisms in activated sludge.
abstract: Two methods that physically separate polyphosphate-accumulating organisms (PAO) from other organisms in activated sludge were developed. The first method used 4'6-diamidino-2-phenylindole dihydrochloride (DAPI) to selectively stain PAO. When excited with light at 340 nm, polyphosphate granules in DAPI-stained cells fluoresce yellow while cells without polyphosphate fluoresce blue. This difference in fluorescent response was used to separate PAO from non-PAO using flow cytometry. The second method consisted of a simple gradient centrifugation to physically separate PAO from non-PAO based on their density differences. Both methods produced cell suspensions with an increased PAO concentration. From an average PAO concentration of approximately 14% in a full-scale process, the DAPI-flow cytometry method produced sorted samples with PAO representing more than 70% of the total cells, while the density gradient method produced an approximate 43 to 48% PAO enrichment. The physical enrichment methods described herein should facilitate the identification and study of PAO that are relevant in full-scale enhanced biological phosphorus removal processes.
authors.affiliation: National Chung-Hsing University, Taichung, Taiwan.
authors.forename: Chun-Hsiung
authors.initials: CH
authors.lastname: Hung
authors.forename: Jordan
authors.initials: J
authors.lastname: Peccia
authors.forename: Julie L
authors.initials: JL
authors.lastname: Zilles
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Noguera
mesh_terms: D001419:Bacteria / Q000302:isolation & purification; D019149:Bioreactors; D005434:Flow Cytometry; D005453:Fluorescence; D010758:Phosphorus / Q000302:isolation & purification; D011122:Polyphosphates / Q000493:pharmacokinetics*; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D011122:Polyphosphates; D012722:Sewage; D010758:Phosphorus