title: Denitrification accelerates granular sludge formation in sequencing batch reactors.
abstract: In this study, the role of denitrification on aerobic granular sludge formation in sequencing batch reactors (SBRs) was investigated. Formation of aerobic granular sludge was faster in SBRs fed with varying concentrations of nitrate or nitrite as compared to control, which received no nitrate or nitrite in the feed. The majority of the fed nitrate or nitrite was denitrified in the anoxic static fill phase, prior to aerobic reaction phase. Sludge characterization showed accumulation of calcium and chemical signature of calcium carbonate in the nitrate-fed SBRs. Feeding of sodium nitroprusside, a known nitric oxide (NO) donor, enhanced aggregation, production of extracellular polymeric substances and formation of aerobic granular sludge. The results support the hypothesis that denitrification facilitates cell aggregation and accelerates aerobic sludge granulation through NO signaling and CaCO3 formation. Nitrate or other intermediates of heterotrophic denitrification, therefore, have a positive effect on aerobic granulation in SBRs.
authors.affiliation: Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, Tamil Nadu, India.
authors.forename: E
authors.initials: E
authors.lastname: Suja
authors.affiliation: Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, Tamil Nadu, India.
authors.forename: Y V
authors.initials: YV
authors.lastname: Nancharaiah
authors.affiliation: Engineering Simulation Studies Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, Tamil Nadu, India.
authors.forename: T V
authors.initials: TV
authors.lastname: Krishna Mohan
authors.affiliation: Biofouling and Biofilm Processes Section, Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, Tamil Nadu, India. Electronic address: vpv@igcar.gov.in.
authors.forename: V P
authors.initials: VP
authors.lastname: Venugopalan
mesh_terms: D000332:Aerobiosis / Q000187:drug effects; D061249:Batch Cell Culture Techniques / Q000295:instrumentation*; D018533:Biomass; D019149:Bioreactors; D058440:Denitrification / Q000187:drug effects; D009566:Nitrates / Q000378:metabolism / Q000494:pharmacology; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000302:isolation & purification; D010316:Particle Size; D012722:Sewage / Q000737:chemistry*; D013054:Spectrophotometry, Atomic
chemical_list: D009566:Nitrates; D009573:Nitrites; D012722:Sewage; D009584:Nitrogen
keywords: Aerobic granular sludge; Denitrification; Nitric oxide signaling; Nitrogen removal; Sequencing batch reactor