Implemented impediment of extracellular electron transfer–dependent anammox process :Unstable nitrogen removal efficiency and decreased abundance of anammox bacteria

The present study investigates the extracellular electron transfer (EET)–dependent anammox process as a promising approach for sustainable wastewater treatment. The study examines the performance and metabolic pathway of the EET–dependent anammox process in comparison to the nitrite–dependent anammox process. The EET–dependent reactor successfully achieved nitrogen removal with a maximum removal efficiency of 93.2%, although it exhibited a lower ability to sustain high nitrogen removal load when compared to the nitrite–dependent anammox process, which poses opportunity and challenge for ammonia–wastewater treatment under applied voltage conditions. Nitrite was identified as a critical factor responsible for the changes in microbial community structure, resulting in a significant reduction in nitrogen removal load in the absence of nitrite. The study further suggests that the Candidatus Kuenenia species could dominate the EET–dependent anammox process, while nitrifying and denitrifying bacteria also contribute to the nitrogen removal in this system.