Determination of critical dissolved oxygen for effective mass transfer of activated sludge flocs based on microelectrode detection technology

• Published in: International journal of environmental science and technology (Tehran) Vol. 19; no. 9; pp. 8243 - 8253
• Main Authors: Shao, Y., Tao, X., Fan, H., Zhou, X.-H., Wang, H., Liu, G.-h., Xu, X., Zhang, J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2022
• Subjects: Aquatic Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Science and Engineering; Original Paper; Soil Science & Conservation; Waste Water Technology; Water Management; Water Pollution Control; Reaction–diffusion kinetics; Microelectrode; Critical DO; Low dissolved oxygen; Internal diffusion resistance
• ISSN: 1735-1472; 1735-2630
• DOI: 10.1007/s13762-021-03669-5

Excessive aeration in wastewater treatment plants (WWTPs) will lead to energy waste. A large number of studies have shown that the control of low dissolved oxygen (DO) operation in WWTPs not only achieves considerable wastewater treatment effects, but also reduces energy waste. In this study, the transfer regulation of substrates and oxygen inside activated sludge flocs was measured under different equipment conditions (particle size of flocs, wastewater quality and sludge retention time of the treatment system) by using a microelectrode. A diffusion–reaction model based on the Monod kinetic model and Fick’s first law of diffusion was established by considering both the internal diffusion resistance and the diffusion rate of oxygen and substrates inside the activated sludge flocs, and the critical DO (DO c ) was calculated by MATLAB software. The results showed that the attenuation of DO concentration in activated sludge flocs increased slightly with the increasing particle size, but it decreased with increasing external DO concentration. A critical DO as low as 0.3 mg/L could be achieved in flocs with low DO concentrations. This study provides strong support to carry out effective and feasible process design and process optimization. In addition, it can further guide WWTPs to achieve energy savings and consumption under stable operation. Graphic abstract