Silicate intervention in Navicula-bacteria symbiosis system: nitrogen removal performance and microbial community

To address the long-term instability of the Navicula-bacteria symbiosis system, this study achieved stable autotrophic nitrogen removal by adding silicates and regulating light/dark cycles. The nitrite accumulation rate reached 92.05 % during the enrichment of Navicula sp. (a diatom genus), which became the dominant algae with the supplementation of silicate and enhanced extracellular polymeric substances (EPS) production. The increased EPS promoted the formation of dense biofilms, facilitating the growth of anaerobic microorganisms. When the ratio of light/dark was adjusted to 8 h:16 h, the system achieved the highest total nitrogen removal rate of 82.69 %. Nitrosomonas (1.26 %) was the dominant bacteria in ammonia-oxidizing bacteria. Denitratisoma (3.75 %) was the dominant bacteria in denitrifying bacteria. Anaerobic ammonia-oxidizing bacteria were naturally enriched without artificial inoculation. The relative abundance of Candidatus Brocadia reached 7.99 %. This study demonstrates an autotrophic pathway for sustainable wastewater treatment.