Characterization of the denitrifying fraction of phosphate accumulating organisms in biological phosphate removal

Jens Meinhold, Carlos D.M. Filipe, Glen T. Daigger, Steven Howard Isaacs

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Results of experimental investigations are presented that strongly support the hypothesis that PAO from activated sludge systems consist of two groups: a) denitrifying PAO (DNPAO) capable of using oxygen and nitrate and b) non-denitrifying PAO (non-DNPAO) only able to use oxygen. Batch experiments were performed in which activated sludge obtained from a pilot scale BIODENIPHO(TM) was submitted to a sequence of anaerobic/anoxic/aerobic, anaerobic/aerobic or anaerobic/anoxic conditions while monitoring the course of NOX-N, NH4-N, PO4-P, PHB and PHV. Several methods for the determination of the two fractions of PAO are performed and compared.

This study extends on previously reported results (Kerrn-Jespersen and Henze, 1993) in that the pH was controlled to around pH 7 to assure that phosphate precipitation was minimal, and in the measurement of PHB and PHV. With regards to the latter, the paper also examines the influence of the size of the internal PHA pool on the anoxic phosphorus uptake rate. Simulations implementing existing models for the growth of non-DNPAO and DNPAO are used to confirm the experimental results and to gain a better understanding of some of the observations. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.
Original languageEnglish
JournalWater Science and Technology
Issue number1
Pages (from-to)31-42
Publication statusPublished - 1999
EventIAWQ Seminar on Modelling and Microbiology of Activated Sludge Processes - Copenhagen, Denmark
Duration: 16 Mar 199818 Mar 1998
Conference number: 4


SeminarIAWQ Seminar on Modelling and Microbiology of Activated Sludge Processes
SponsorInternational Association on Water Quality


  • phosphorus removal
  • denitrification
  • non-DNPAO
  • activated sludge
  • simulation
  • saturation kinetics
  • PHB

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