Performance and adsorption mechanism of microbial fuel cells in treating industrial wastewater with high salt and nitrogen content

Inorganic salts and nitrogen compounds are prevalent in wastewater from chemical, pharmaceutical, and petrochemical industries. Nitrogen-containing wastewater in high-salt environments was treated in an anaerobic fluidised bed microbial fuel cell (AFB-MFC) with carbon brush biofilm anodes and macroporous adsorption resin (MAR) as a multifunctional biofilm carrier. During the experiment, the DO value of the influent was maintained between 0.2-0.5 mg/L, and the nitrogen concentrations in the influent were 0.3, 0.5, and 1.0 g/L, respectively. Materials Studio (MS) software was used to construct nitrogen-containing compounds and MAR models. The simulation result indicated that MAR exhibited the best adsorption performance on nitrite nitrogen, with an adsorption heat of 117.7985 kJ/mol. MAR effectively removes nitrogen-containing compounds through van der Waals forces and hydrogen bonding interactions. The simulation closely matched experimental results, with a high R² (>0.99) indicating strong regression significance. The highest removal efficiency of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen was 97.97 ± 0.97%, 98.81 ± 1%, and 99 ± 0.47%, respectively. The results showed that the desalination efficiency was 55%, 41.5%, and 27% at salinities of 10, 20, and 30 g/L, respectively. The maximum output voltage and power density achieved using carbon brush as biofilm anodes in the AFB-MFC were 651.34 mV and 174.97 mW/m², respectively. The high-throughput sequencing analysis results revealed a significant relative abundance of the dominant electroactive bacteria present on the carbon brush, such as Proteobacteria, Firmicutes, Bacteroidota, and Chloroflexi, and also identified such superior denitrification bacteria as Citrobacter, Corynebacterium, Pseudomonas, and Castellaniella etc.