title: Rapid and successful start-up of anammox process by immobilizing the minimal quantity of biomass in PVA-SA gel beads.
abstract: Rapid start-up of anaerobic ammonium oxidation (anammox) process in up-flow column reactors was successfully achieved by immobilizing minimal quantity of biomass in polyvinyl alcohol (PVA)-sodium alginate (SA) gel beads. The changes in the reactor performance (i.e., nitrogen removal rate; NRR) were monitored with time. The results demonstrate that the reactor containing the immobilized biomass concentration of 0.33 g-VSS L(-1) achieved NRR of 10.8 kg-N m(-3) d(-1) after 35-day operation, whereas the reactor containing the granular biomass of 2.5 g-VSS L(-1) could achieve only NRR of 3.5 kg-N m(-3) d(-1). This indicates that the gel immobilization method requires much lower seeding biomass for start-up of anammox reactor. To explain the better performance of the immobilized biomass, the biological and physicochemical properties of the immobilized biomass were characterized and compared with the naturally aggregated granular biomass. Effective diffusion coefficient (De) in the immobilized biomass was directly determined by microelectrodes and found to be three times higher than one in the granular biomass. High anammox activity (i.e., NH4(+) and NO2(-) consumption rates) was evenly detected throughout the gel beads by microelectrodes due to faster and deeper substrate transport. In contrast, anammox activity was localized in the outer layers of the granular biomass, indicating that the inner biomass could not contribute to the nitrogen removal. This difference was in good agreement with the spatial distribution of microbes analysed by fluorescence in situ hybridization (FISH). Based on these results, PVA-SA gel immobilization is an efficient strategy to initiate anammox reactors with minimal quantity of anammox biomass.
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Ali
authors.affiliation: Department of Civil Engineering, Nagaoka National College of Technology, 888 Nishikatakaimachi, Nagaoka, Niigata 940-0834, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Oshiki
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Lashitha
authors.initials: L
authors.lastname: Rathnayake
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Sapporo, Hokkaido 060-8628, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Satoh
authors.affiliation: Division of Environmental Engineering, Faculty of Engineering, Hokkaido University, North 13, West 8, Sapporo, Hokkaido 060-8628, Japan. Electronic address: sokabe@eng.hokudai.ac.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okabe
mesh_terms: D000464:Alginates; D064751:Ammonium Compounds / Q000737:chemistry / Q000378:metabolism*; D000693:Anaerobiosis; D018533:Biomass; D019149:Bioreactors; D005782:Gels; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011142:Polyvinyl Alcohol; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D000464:Alginates; D064751:Ammonium Compounds; D005782:Gels; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D011142:Polyvinyl Alcohol
keywords: Anaerobic ammonium oxidation; Effective diffusion coefficient; Gel immobilization; Start-up of anammox process