Enhancing methane production of anaerobic sludge digestion by microaeration: Enzyme activity stimulation, semi-continuous reactor validation and microbial community analysis

Effects of microaeration pretreatment on sludge hydrolysis, biogas production and microbial community structure in anaerobic digestion (AD) were investigated by bench-scale tests and semi-continuous experiments. Bench tests showed that microaeration led to the release of dissolved organic matters, generation of volatile fatty acids and stimulation of enzyme activity. Correlation analysis showed that methane production was significantly correlated with the activity of a-glucosidase at 0.01 level, and with protease activity, released polysaccharides and VFAs at 0.05 level. Semi-continuous experiments showed that microaeration accelerated the utilization of organic matters, increased biogas production by 16.4%, enhanced methane content in biogas, and improved sludge dewaterability. Microbial community structure analysis showed that microaeration promoted enrichment of hydrolytic and fermentative bacteria in AD reactor rather than methanogenic bacteria, and aceticlastic methanogenesis was the main methanogenic pathway for methane production.