The Microbiology of Biological Phosphorus Removal in Activated Sludge Systems

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FEMS Microbiology Reviews 27 (2003) 99^127

www.fems-microbiology.org

The microbiology of biological phosphorus removal in activated sludge systems Robert J. Seviour à , Takashi Mino, Motoharu Onuki
Institute of Environmental Studies, Graduate School of Frontier Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan Received 11 December 2002; received in revised form 18 February 2003; accepted 20 February 2003 First published online 20 March 2003

Abstract
Activated sludge systems are designed and operated globally to remove phosphorus microbiologically, a process called enhanced biological phosphorus removal (EBPR). Yet little is still known about the ecology of EBPR processes, the microbes involved, their functions there and the possible reasons why they often perform unreliably. The application of rRNA-based methods to analyze EBPR community structure has changed dramatically our understanding of the microbial populations responsible for EBPR, but many substantial gaps in our knowledge of the population dynamics of EBPR and its underlying mechanisms remain. This review critically examines what we once thought we knew about the microbial ecology of EBPR, what we think we now know, and what still needs to be elucidated before these processes can be operated and controlled more reliably than is currently possible. It looks at the history of EBPR, the currently available biochemical models, the structure of the microbial communities found in EBPR systems, possible identities of the bacteria responsible, and the evidence why these systems might operate suboptimally. The review stresses the need to extend what have been predominantly laboratory-based studies to full-scale operating plants. It aims to encourage microbiologists and process engineers to collaborate more closely and to bring an interdisciplinary approach to bear on this complex ecosystem. ß 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved. Keywords : Activated sludge; Enhanced biological phosphorus removal; Phosphorus accumulating organism ; ‘G-bacteria’; Glycogen accumulating organism ; Rhodocyclus

Contents 1. 2. 3. 4. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some history of EBPR processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Which chemical transformations characterize EBPR biomass? . . . . . . . . . . . . . . . . . . . . . The biochemistry of EBPR systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. EBPR metabolism with acetate as sole carbon source . . . . . . . . . . . . . . . . . . . . . . . . 4.2. EBPR metabolism with substrates other than acetate . . . . . . . . . . . . . . . . . . . . . . . . . The nature and role of polyP storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The microbiology of EBPR ^ the culture-dependent approach . . . . . . . . . . . . . . . . . . . . . The microbiology of EBPR ^ the culture-independent approach: chemical markers . . . . . . The microbiology of EBPR ^ the culture-independent approach: molecular microbial ecology of EBPR communities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What have molecular techniques revealed about the nature of EBPR microbial communities? .............................................................. 100 101 101 102 102 104 105 106 107 107 108

5. 6. 7. 8. 9.

* Corresponding author. Present address: Biotechnology Research Centre, La Trobe University, Bendigo, Vic. 3552, Australia. E-mail address : r.seviour@latrobe.edu.au (R.J. Seviour). Abbreviations : CFB, Cytophaga^Flavobacterium^Bacteroides division; DAPI, diamidino phenyl indole; DGGE, denaturing gradient gel electrophoresis; DNPAO, denitrifying polyP accumulating organisms ; EBPR,...
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