title: Identification of inorganic and organic species of phosphorus and its bio-availability in nitrifying aerobic granular sludge.
abstract: Phosphorus (P) recovery from sewage sludge is necessary for a sustainable development of the environment and thus the society due to gradual depletion of non-renewable P resources. Aerobic granular sludge is a promising biotechnology for wastewater treatment, which could achieve P-rich granules during simultaneous nitrification and denitrification processes. This study aimed to disclose the changes in inorganic and organic P species and their correlation with P mobility and bio-availability in aerobic granules. Two identical square reactors were used to cultivate aerobic granules, which were operated for 120 days with influent ammonia nitrogen (NH₄-N) of 100 mg/L before day 60 and then increased to 200 mg/L during the subsequent 60 days (chemical oxygen demand (COD) was kept constant at 600 mg/L). The aerobic granules exhibited excellent COD removal and nitrification efficiency. Results showed that inorganic P (IP) was about 61.4-67.7% of total P (TP) and non-apatite inorganic P (NAIP) occupied 61.9-70.2% of IP in the granules. The enrichment amount of NAIP and apatite P (AP) in the granules had strongly positive relationship with the contents of metal ions, i.e. Fe and Ca, respectively accumulated in the granules. X-ray diffraction (XRD) analysis and solution index calculation demonstrated that hydroxyapatite (Ca₅(PO₄)₃(OH)) and iron phosphate (Fe₇(PO₄)₆) were the major P minerals in the granules. Organic P (OP) content maintained around 7.5 mg per gram of biomass in the aerobic granules during the 120 days' operation. Monoester phosphate (21.8% of TP in extract), diester phosphate (1.8%) and phosphonate (0.1%) were identified as OP species by Phosphorus-31 nuclear magnetic resonance (³¹P NMR). The proportion of NAIP + OP to TP was about 80% in the granules, implying high potentially mobile and bio-available P was stored in the nitrifying aerobic granules. The present results provide a new insight into the characteristics of P species in aerobic granules, which could be helpful for developing P removal and recovery techniques through biological wastewater treatment.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Wenli
authors.initials: W
authors.lastname: Huang
authors.forename: Wei
authors.initials: W
authors.lastname: Cai
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Lei
authors.forename: Zhenya
authors.initials: Z
authors.lastname: Zhang
authors.forename: Joo Hwa
authors.initials: JH
authors.lastname: Tay
authors.forename: Duu-Jong
authors.initials: DJ
authors.lastname: Lee
mesh_terms: D000332:Aerobiosis; D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D008903:Minerals / Q000737:chemistry; D058465:Nitrification; D010755:Organophosphates / Q000737:chemistry*; D017553:Phosphorus Compounds / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D008903:Minerals; D010755:Organophosphates; D017553:Phosphorus Compounds; D012722:Sewage