title: Nitrite survival and nitrous oxide production of denitrifying phosphorus removal sludges in long-term nitrite/nitrate-fed sequencing batch reactors.
abstract: Nitrite-based phosphorus (P) removal could be useful for innovative biological P removal systems where energy and carbon savings are a priority. However, using nitrite for denitrification may cause nitrous oxide (N2O) accumulation and emissions. A denitrifying nitrite-fed P removal system [Formula: see text] was successfully set up in a sequencing batch reactor (SBR) and was run for 210 days. The maximum pulse addition of nitrite to [Formula: see text] was 11 mg NO2(-)-N/L in the bulk, and a total of 34 mg NO2(-)-N/L of nitrite was added over three additions. Fluorescent in situ hybridization results indicated that the P-accumulating organisms (PAOs) abundance was 75 ± 1.1% in [Formula: see text] , approximately 13.6% higher than that in a parallel P removal SBR using nitrate [Formula: see text] . Type II Accumulibacter (PAOII) (unable to use nitrate as an electron acceptor) was the main PAOs species in [Formula: see text] , contributing 72% to total PAOs. Compared with [Formula: see text] , [Formula: see text] biomass had enhanced nitrite/free nitrous acid (FNA) endurance, as demonstrated by its higher nitrite denitrification and P uptake rates. N2O accumulated temporarily in [Formula: see text] after each pulse of nitrite. Peak N2O concentrations in the bulk for [Formula: see text] were generally 6-11 times higher than that in [Formula: see text] ; these accumulations were rapidly denitrified to nitrogen gases. N2O concentration increased rapidly in nitrate-cultivated biomass when 5 or 10 mg NO2(-)-N/L per pulse was added. Whereas, N2O accumulation did not occur in nitrite-cultivated biomass until up to 30 mg NO2(-)-N/L per pulse was added. Long-term acclimation to nitrite and pulse addition of nitrite in [Formula: see text] reduced the risk of nitrite accumulation, and mitigated N2O accumulation and emissions from denitrifying P removal by nitrite.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China. Electronic address: yayi.wang@tongji.edu.cn.
authors.forename: Yayi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhou
authors.affiliation: School of Chemical Engineering, The University of Queensland, St Lucia, Brisbane 4072, Australia.
authors.forename: Liu
authors.initials: L
authors.lastname: Ye
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Cranfield University, Cranfield MK43 0AL, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Stephenson
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Siping Road, Shanghai 200092, PR China.
authors.forename: Xuxin
authors.initials: X
authors.lastname: Jiang
mesh_terms: D000704:Analysis of Variance; D019149:Bioreactors; D058440:Denitrification / Q000502:physiology*; D009573:Nitrites / Q000032:analysis; D009609:Nitrous Oxide / Q000378:metabolism; D010758:Phosphorus / Q000302:isolation & purification; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D009573:Nitrites; D009609:Nitrous Oxide; D010758:Phosphorus; D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Denitrifying phosphorus removal; Denitrifying phosphorus-accumulating organisms; Free nitrous acid; Glycogen-accumulating organisms; Nitrite; Nitrous oxide