Enhanced decomposition of waste activated sludge via anodic oxidation for methane production and bioenergy recovery

Published Date
January 2016, Vol.106:161–169, doi:10.1016/j.ibiod.2015.10.020

Author 

• Zhiqiang Zhao
• Yaobin Zhang ^,
• Qilin Yu
• Weican Ma
• Jiaqi Sun
• Xie Quan

• Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China

Received 29 March 2015. Revised 27 October 2015. Accepted 27 October 2015. Available online 8 November 2015. 

Highlights

• Sludge hydrolysis was significantly enhanced via anodic oxidation of MEC.
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  Organic matters decomposition rate was also improved in the MEC reactor.
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  An extra 28% CH₄ yield was obtained after 24 days experiments.
• •
  Electric energy supply was 1/5 of energy income from the increased methane.

Abstract

Anaerobic digestion operated in microbial electrolysis cells (MECs) may have a higher methane production since the potential cathodic reduction of carbon dioxide. However, the complicated organic components in municipal sludge retard the sludge hydrolysis and limit the efficiency of methanogenesis. Sludge hydrolysis and its effects on methanogenesis and organic matter removal in a single-chamber MEC were investigated in this study. As compared with the control reactor without electric field, total chemical oxygen demand (TCOD) removal and methane production in MEC with applied voltage of 0.8 V increased by 26% and 28%, respectively. Energy income from the increased methane was about five folds of the electric energy supply. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis indicated that anodic oxidation of MEC significantly improved the disintegration of sludge flocs and cell walls. Anodic Coulombic efficiency and current density further revealed that anodic oxidation coupled with cathodic reduction of carbon dioxide was the predominant mechanism in the improvement of sludge decomposition and methane production during the initial fermentation, which hereby accelerated the rate of sludge hydrolysis.

Graphical abstract

Keywords

• Anaerobic sludge digestion
• Sludge hydrolysis
• Microbial electrolysis cell (MEC)
• Anodic oxidation

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  Corresponding author.

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