title: High-temperature EBPR process: the performance, analysis of PAOs and GAOs and the fine-scale population study of Candidatus "Accumulibacter phosphatis".
abstract: The applicability of the enhanced biological phosphorus removal (EBPR) process for the removal of phosphorus in warm climates is uncertain due to frequent reports of EBPR deterioration at temperature higher than 25 °C. Nevertheless, a recent report on a stable and efficient EBPR process at 28 °C has inspired the present study to examine the performance of EBPR at 24 °C-32 °C, as well as the PAOs and GAOs involved, in greater detail. Two sequencing batch reactors (SBRs) were operated for EBPR in parallel at different temperatures, i.e., SBR-1 at 28 °C and SBR-2 first at 24 °C and subsequently at 32 °C. Both SBRs exhibited high phosphorus removal efficiencies at all three temperatures and produced effluents with phosphorus concentrations less than 1.0 mg/L during the steady state of reactor operation. Real-time quantitative polymerase chain reaction (qPCR) revealed Accumulibacter-PAOs comprised 64% of the total bacterial population at 24 °C, 43% at 28 °C and 19% at 32 °C. Based on fluorescent in situ hybridisation (FISH), the abundance of Competibacter-GAOs at both 24 °C and 28 °C was rather low (<10%), while it accounted for 40% of the total bacterial population at 32 °C. However, the smaller Accumulibacter population and larger population of Competibacter at 32 °C did not deteriorate the phosphorus removal performance. A polyphosphate kinase 1 (ppk1)-based qPCR analysis on all studied EBPR processes detected only Accumulibacter clade IIF. The Accumulibacter population shown by 16S rRNA and ppk1 was not significantly different. This finding confirmed the existence of single clade IIF in the processes and the specificity of the clade IIF primer sets designed in this study. Habitat filtering related to temperature could have contributed to the presence of a unique clade. The clade IIF was hypothesised to be able to perform the EBPR activity at high temperatures. The clade's robustness most likely helps it to fit the high-temperature EBPR sludge best and allows it not only to outcompete other Accumulibacter clades but coexist with GAOs without compromising EBPR activity.
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Ying Hui
authors.initials: YH
authors.lastname: Ong
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia. Electronic address: adeline@um.edu.my.
authors.forename: Adeline Seak May
authors.initials: ASM
authors.lastname: Chua
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, Japan.
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Fukushima
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Gek Cheng
authors.initials: GC
authors.lastname: Ngoh
authors.affiliation: Department of Socio-Cultural Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shoji
authors.affiliation: Wastewater and Sludge Management Division, Water Quality Control Department, National Institute for Land and Infrastructure Management, Asahi 1, Tsukuba, Ibaraki 305-0804, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Michinaka
mesh_terms: D001420:Bacteria, Aerobic / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000378:metabolism; D019149:Bioreactors; D006358:Hot Temperature; D010758:Phosphorus / Q000378:metabolism*; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000378:metabolism; D020560:Proteobacteria / Q000302:isolation & purification* / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage; D010758:Phosphorus; D017856:Phosphotransferases (Phosphate Group Acceptor); C022424:polyphosphate kinase
keywords: Accumulibacter clades; Enhanced biological phosphorus removal; Glycogen accumulating organisms; Polyphosphate accumulating organisms; Temperature; ppk1