title: Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors.
abstract: A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy.
authors.affiliation: Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, India. Electronic address: tvkm@igcar.gov.in.
authors.forename: Tulasi Venkata
authors.initials: TV
authors.lastname: Krishna Mohan
authors.affiliation: Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, India; School of Biosciences and Technology, VIT University, Vellore 632014, India.
authors.forename: Kadali
authors.initials: K
authors.lastname: Renu
authors.affiliation: Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, India.
authors.forename: Yarlagadda Venkata
authors.initials: YV
authors.lastname: Nancharaiah
authors.affiliation: Waste Immobilization Plant, NRB, Bhabha Atomic Research Centre, Kalpakkam 603102, India.
authors.forename: Pedapati Murali
authors.initials: PM
authors.lastname: Satya Sai
authors.affiliation: Water and Steam Chemistry Division, Bhabha Atomic Research Centre, Kalpakkam 603102, India.
authors.forename: Vayalam Purath
authors.initials: VP
authors.lastname: Venugopalan
mesh_terms: D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D058440:Denitrification; D009566:Nitrates / Q000302:isolation & purification* / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*
chemical_list: D009566:Nitrates; D009573:Nitrites; D012722:Sewage; D002244:Carbon; D009584:Nitrogen
keywords: Carbon to nitrogen ratio; Denitrification; Granular sludge; High strength nitrate; Nitrite accumulation