Abstract
Most anaerobic digestion reactors are operated under mesophilic and thermophilic conditions, requiring high levels of heat energy to maintain high temperatures. If an optimized method existed for psychrotrophic anaerobic digestion (PAD), it would have outstanding economic and environmental benefits as an alternative to mesophilic or thermophilic reactors. Therefore, this study aimed to investigate the conditions and corresponding mechanism to optimize PAD for producing high yields of methane. We found that intermittent bioaugmentation with mesophilic propionate-degrading consortia showed enhanced methane production back to uninhibited levels in a psychrotrophic anaerobic reactor under volatile fatty acid stress, with long-term effectiveness for 14 hydraulic retention times. The increase in acetoclastic methanogens (Methanothrix harundinacea and Methanosarcina flavescens) stimulated methanogenesis in the psychrotrophic system. Metagenomic analysis showed that bacteria carried more diverse cold-regulating gene sets and had higher DNA replication rates than methanogens, explaining the higher cold tolerance of bacterial community than that of methanogen community. By coupling reactor performance with microbial metabolic analysis, this study is the first to provide comprehensive findings that intermittent bioaugmentation with methanogenic consortia is a promising strategy to boost the PAD process.
Published Version
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