title: Characterization of sulfate-reducing granular sludge in the SANI(®) process.
abstract: Hong Kong practices seawater toilet flushing covering 80% of the population. A sulfur cycle-based biological nitrogen removal process, the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI(®)) process, had been developed to close the loop between the hybrid water supply and saline sewage treatment. To enhance this novel process, granulation of a Sulfate-Reducing Up-flow Sludge Bed (SRUSB) reactor has recently been conducted for organic removal and provision of electron donors (sulfide) for subsequent autotrophic denitrification, with a view to minimizing footprint and maximizing operation resilience. This further study was focused on the biological and physicochemical characteristics of the granular sulfate-reducing sludge. A lab-scale SRUSB reactor seeded with anaerobic digester sludge was operated with synthetic saline sewage for 368 days. At 1 h nominal hydraulic retention time (HRT) and 6.4 kg COD/m(3)-d organic loading rate, the SRUSB reactor achieved 90% COD and 75% sulfate removal efficiencies. Granular sludge was observed within 30 days, and became stable after 4 months of operation with diameters of 400-500 μm, SVI5 of 30 ml/g, and extracellular polymeric substances of 23 mg carbohydrate/g VSS. Fluorescence in situ hybridization (FISH) analysis revealed that the granules were enriched with abundant sulfate-reducing bacteria (SRB) as compared with the seeding sludge. Pyrosequencing analysis of the 16S rRNA gene in the sulfate-reducing granules on day 90 indicated that the microbial community consisted of a diverse SRB genera, namely Desulfobulbus (18.1%), Desulfobacter (13.6%), Desulfomicrobium (5.6%), Desulfosarcina (0.73%) and Desulfovibrio (0.6%), accounting for 38.6% of total operational taxonomic units at genera level, with no methanogens detected. The microbial population and physicochemical properties of the granules well explained the excellent performance of the granular SRUSB reactor.
authors.affiliation: Department of Civil & Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Tianwei
authors.initials: T
authors.lastname: Hao
authors.forename: Li
authors.initials: L
authors.lastname: Wei
authors.forename: Hui
authors.initials: H
authors.lastname: Lu
authors.forename: Hokwong
authors.initials: H
authors.lastname: Chui
authors.forename: Hamish R
authors.initials: HR
authors.lastname: Mackey
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
authors.forename: Guanghao
authors.initials: G
authors.lastname: Chen
mesh_terms: D001421:Bacteria, Anaerobic / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D019149:Bioreactors; D020564:Deltaproteobacteria / Q000235:genetics / Q000378:metabolism; D058440:Denitrification; D003901:Desulfovibrio / Q000235:genetics / Q000378:metabolism; D006723:Hong Kong; D017404:In Situ Hybridization, Fluorescence; D059013:Microbial Consortia / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D058465:Nitrification; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S; D012722:Sewage / Q000032:analysis / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage; D013431:Sulfates
keywords: Granular sludge characterization; SANI(®) process; Sulfate-reducing sludge granulation