title: Partial nitritation of stored source-separated urine by granular activated sludge in a sequencing batch reactor.
abstract: The combination of partial nitritation (PN) and anaerobic ammonium oxidation (anammox) has been proposed as an ideal process for nitrogen removal from source-separated urine, while the high organic matters in urine cause instability of single-stage PN-anammox process. This study aims to remove the organic matters and partially nitrify the nitrogen in urine, producing an ammonium/nitrite solution suitable for anammox. The organic matters in stored urine were used as the electron donors to achieve 40% total nitrogen removal in nitritation-denitrification process in a sequencing batch reactor (SBR). Granular aggregates were observed and high mixed liquor suspended solids (9.5 g/L) were maintained in the SBR. Around 70-75% ammonium was oxidized to nitrite under the volumetric loading rates of 3.23 kg chemical oxygen demand (COD)/(m3d) and 1.86 kg N/(m3d), respectively. The SBR produced an ammonium/nitrite solution free of biodegradable organic matters, with a NO2--N:NH4+-N of 1.24 ± 0.13. Fluorescence in situ hybridization images showed that Nitrosomonas-like ammonium-oxidizing bacteria, accounting for 7.2% of total bacteria, located in the outer layer (25 μm), while heterotrophs distributed homogeneously throughout the granular aggregates. High concentrations of free ammonia and nitrous acids in the reactor severely inhibited the growth of nitrite-oxidizing bacteria, resulting in their absence in the granular sludge. The microbial diversity analysis indicated Proteobacteria was the predominant phylum, in which Pseudomonas was the most abundant genus.
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China.
authors.forename: Xiujun
authors.initials: X
authors.lastname: Tian
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China.
authors.forename: Song
authors.initials: S
authors.lastname: Yao
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China. lijy@bjtu.edu.cn.
authors.forename: Jiuyi
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Municipal and Environmental Engineering, Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard, Beijing Jiaotong University, Beijing, 100044, China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Wang
authors.affiliation: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710048, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yao
authors.affiliation: School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an, 710048, China.
authors.forename: Dangcong
authors.initials: D
authors.lastname: Peng
keywords: Fluorescence in situ hybridization; Granular sludge; Nitrogen removal; Partial nitritation; Source-separated urine