Chitosan-Fe3O4 composites enhance anaerobic digestion of liquor wastewater under acidic stress

[Display omitted] •Acid inhibition was alleviated by the addition of chitosan-Fe3O4.•Chitosan-Fe3O4 promoted the utilization of organic acids under acidic pressure.•Chitosan-Fe3O4 supplemented could enhance the electron transfer activity.•Chitosan-Fe3O4 enriched microbes related to direct interspecies electron transfer. Acid stress in the anaerobic digestion process of liquor wastewater leads to low anaerobic treatment efficiency. Herein, chitosan-Fe3O4 was prepared, and its effects on anaerobic digestion processes under acid stress were studied. Results showed that chitosan-Fe3O4 increased the methanogenesis rate of anaerobic digestion of acidic liquor wastewater by 1.5–2.3 times and accelerated the restoration of acidified anaerobic systems. The analysis of sludge characteristics showed that chitosan-Fe3O4 promoted the secretion of proteins and humic substances in extracellular polymeric substances and increased the electron transfer activity of the system by 71.4%. Microbial community analysis indicated that chitosan-Fe3O4 enriched the abundance of Peptoclostridium, and Methanosaeta participated in direct interspecies electron transfer. Chitosan-Fe3O4 could promote the direct interspecies electron transfer pathway to maintain stable methanogenesis. These methods and results regarding the use of chitosan-Fe3O4 could be referred to for improving the efficiency of anaerobic digestion of high concentration organic wastewater under acid inhibition.