Potential mechanism of enhanced anaerobic degradation of high concentration phenol-containing wastewater by hazardous waste fly ash with high iron content: Direct interspecies electron transport pathway

[Display omitted] Micron-grade high iron-containing fly ash (MHIFA)—a processed hazardous waste containing Fe3O4—was added to an up-flow anaerobic sludge blanket reactor to improve the removal performance of high concentration phenol-containing wastewater. The chemical oxygen demand and total phenol removal efficiency with MHIFA were 72.13% and 81.83%, respectively. Moreover, MHIFA addition increased the contents of coenzyme F420 and extracellular polymeric substances, as well as higher electron transport system activity in activated sludge. Additionally, microbial community analysis revealed that the total methanogens contents increased at genera level, producing an increase in methane production, while enriched Geobacter along with archaea Methanothrix might collaborate in direct interspecies electron transfer (DIET) by MHIFA stimulation, promoting the effect of phenolic compound fermentation. Finally, this technology allows for resource utilization of hazardous waste and enhances anaerobic degradation of toxic and refractory pollutants.