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Micro-analysis of nitrogen transport and conversion inside activated sludge flocs using microelectrodes |
Lei WANG, Yongtao LV( ), Xudong WANG, Yongzhe YANG, Xiaorong BAI |
| School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China |
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Abstract To investigate the nitrogen transport and conversion inside activated sludge flocs, micro-profiles of O2, NH4+, NO2–, NO3–, and pH were measured under different operating conditions. The flocs were obtained from a laboratory-scale sequencing batch reactor. Nitrification, as observed from interfacial ammonium and nitrate fluxes, was higher at pH 8.5, than at pH 6.5 and 7.5. At pH 8.5, heterotrophic bacteria used less oxygen than nitrifying bacteria, whereas at lower pH heterotrophic activity dominated. When the ratio of C to N was decreased from 20 to 10, the ammonium uptake increased. When dissolved oxygen (DO) concentration in the bulk liquid was decreased from 4 to 2 mg·L-1, nitrification decreased, and only 25% of the DO influx into the flocs was used for nitrification. This study indicated that nitrifying bacteria became more competitive at a higher DO concentration, a higher pH value (approximately 8.5) and a lower C/N.
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| Keywords
nitrogen transport
activated sludge flocs
heterotrophic bacteria
nitrifying bacteria
microelectrodes
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Corresponding Author(s):
LV Yongtao,Email:hybos2000@126.com
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Issue Date: 05 December 2011
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