Journal of Environmental Biology

Long-term evolution of an activated sludge system under low

dissolved oxygen conditions

Jinsong Guo*, Yufeng Xu, Youpeng Chen, Leilei Fan and Fang Fang

Key Laboratory of the Three Gorges Reservoir  Region?s Eco-environments, Ministry of Education, Chongqing University,

Chongqing, 400045, P. R. China

*Corresponding Author email : guo0768@cqu.edu.cn

Publication Data

Paper received:

15 June 2012

Revised received:

15 August 2012

Accepted:

15 November 2012

Abstract

This study aims to evaluate the impacts of low dissolved oxygen (DO) levels on activated sludge performance. Two sequencing batch reactors (SBR), each with a working volume of 10 l, were investigated with different DO levels. Compared with high DO conditions (above 2 mg l-1 on average), low DO conditions in the SBR did not result in poor sludge bulking, lower chemical oxygen demand, and ammonium removal efficiency. Moreover, simultaneous nitrification and denitrification (SND) via nitrite and shortcut nitrification-denitrification were carried out under low DO levels. The average efficiencies of SND and nitrite accumulation ratios (NAR) in reactors A and B were 10.6 and 60.4%, respectively, under high DO levels and 4.1 and 76%, respectively, under low DO levels. Scanning electron microscopy revealed that the main types of bacteria in reactor A were spherical and short rod-shaped bacteria, whereas those in reactor B were long rod-shaped bacteria and filamentous bacteria. Thus, the appropriate DO concentration created excellent microbial community structures, which helped the biological systems to perform well under low DO level operating conditions.

Key words

Low dissolved oxygen, Microbial activity, Activated Sludge performance, Nitrification, Denitrification

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