Synergy of Fe-modified zeolite and light stimulation on ammonia-stressed anaerobic digestion: Performance, microbial community and metabolic pathway

This study introduced a novel hybrid system incorporating iron-modified zeolite (Fe-Z) with intermittent light stimulation for addressing ammonia-inhibited AD. The dynamics of Fe transformation and metagenomic profiling highlighted complete Fe3+ reduction and promoted Fe assimilation in the hybrid system, supporting the microbial stimulation and coenzyme biosynthesis. Moreover, the predominance of syntrophic organic oxidizers (Anaerolineae and Clostridia), nitrate reducers (Betaproteobacteria and Epsilonproteobacteria) and robust methanogens (Methanosarcinaceae and Methanosaetaceae) in hybrid system aided in the effective breakdown of organic acids, nitrogen removal and CH4 conversion. These electroactive community adopted energetically favorable electron transport pathways for intracellular ATP conversation and extracellular interspecies cooperation, which collectively energized the carbohydrate metabolism and methanogenic pathways.