title: A new biological phosphorus removal process in association with sulfur cycle.
abstract: Hong Kong has practiced seawater toilet flushing since 1958, saving 750,000 m(3) freshwater every day. A high sulfate-to-COD ratio (>1.25 mg SO4/mg COD) in the saline sewage resulting from this practice has enabled us to develop the Sulfate reduction Autotrophic denitrification and Nitrification Integrated (SANI(®)) process with minimal sludge production. This study seeks to expand the SANI process into an enhanced biological phosphorus removal (EBPR) process. A sulfur cycle associated EBPR was explored in an alternating anaerobic/oxygen-limited aerobic sequencing batch reactor with acetate fed as sole electron donor and sulfate as sulfur source at a total organic carbon to sulfur ratio of 1.1-3.1 (mg C/mg S). Phosphate uptake and polyphosphate formation was observed in this reactor that sustained high phosphate removal (20 mg P/L removed with 320 mg COD/L). This new EBPR process was supported by six observations: 1) anaerobic phosphate release associated with acetate uptake, poly-phosphate hydrolysis, poly-hydroxyalkanoate (PHA) (and poly-S(2-)/S(0)) formation and an "aerobic" phosphate uptake associated with PHA (and poly-S(2-)/S(0)) degradation, and polyphosphate formation; 2) a high P/VSS ratio (>0.16 mg P/mg VSS) and an associated low VSS/TSS ratio (0.75) characteristic of conventional PAOs; 3) a lack of P-release and P-uptake with formaldehyde inactivation and autoclaved sterilized biomass; 4) an absence of chemical precipitated P crystals as determined by XRD analysis; 5) a sludge P of more than 90% polyphosphate as determined by sequential P extraction; and 6) microscopically, observed PHA, poly-P and S globules in the biomass.
authors.affiliation: Department of Civil & Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: George A
authors.initials: GA
authors.lastname: Ekama
authors.forename: Hui
authors.initials: H
authors.lastname: Lu
authors.forename: Ho-Kwong
authors.initials: HK
authors.lastname: Chui
authors.forename: Wen-Tso
authors.initials: WT
authors.lastname: Liu
authors.forename: Damir
authors.initials: D
authors.lastname: Brdjanovic
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
authors.forename: Guang-Hao
authors.initials: GH
authors.lastname: Chen
mesh_terms: D000085:Acetates / Q000032:analysis; D052818:Autotrophic Processes / Q000187:drug effects; D001419:Bacteria / Q000187:drug effects / Q000378:metabolism; D061249:Batch Cell Culture Techniques / Q000295:instrumentation; D001673:Biodegradation, Environmental / Q000187:drug effects; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D058440:Denitrification / Q000187:drug effects; D006723:Hong Kong; D058465:Nitrification / Q000187:drug effects; D010100:Oxygen / Q000494:pharmacology; D010710:Phosphates / Q000032:analysis; D010758:Phosphorus / Q000302:isolation & purification*; D013431:Sulfates / Q000032:analysis; D013455:Sulfur / Q000378:metabolism*
chemical_list: D000085:Acetates; D010710:Phosphates; D013431:Sulfates; D010758:Phosphorus; D013455:Sulfur; D010100:Oxygen