title: Impact of operating conditions on nitrogen removal using cyclic activated sludge technology (CAST).
abstract: In this study, the nitrogen removal performance of a municipal wastewater treatment plant that employs cyclic activated sludge technology (CAST) was evaluated. The impact of key operational conditions such as temperature, dissolved oxygen (DO) concentrations and operating modes were examined in parallel. During summer, when the operating temperature ranged from 27-30 degrees C, the NH(4)(+)-N and total nitrogen (TN) removal efficiencies were 51 +/- 7% and 42 +/- 7%, respectively, and simultaneous nitrification and denitrification (SND) was considered to be the major nitrogen removal mechanism. In contrast, at a low operating temperature of 10-15 degrees C, the DO concentration increased from 0.7 to 3.0 mg/L; however, the NH(4)(+)-N and TN removals were both inefficient due to poor biomass activities, which was demonstrated by a lower specific oxygen uptake rate (SOUR) of 1.2 mg O(2)/g SS. h (15 degrees C). Moreover, a 3h-mode for the CAST process was preferable during winter because the effluent wastewater quality was similar to that obtained when the 4h-mode was used. The extremely low organic loading was the primary reason for the poor bioactivity of the sludge in the CAST system, and this eventually led to deterioration of the nitrogen removal efficiencies.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, PR China. yayi.wang@tongji.edu.cn
authors.forename: Ya Y
authors.initials: YY
authors.lastname: Wang
authors.forename: Zhao X
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Yan
authors.forename: Nai Y
authors.initials: NY
authors.lastname: Gao
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Ming H
authors.initials: MH
authors.lastname: Ren
mesh_terms: D009584:Nitrogen / Q000302:isolation & purification* / Q000378:metabolism; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D012722:Sewage; D009584:Nitrogen