Manganese cycle-mediated synchronous bacteria-algae/anammox coupled denitrification system under low-temperature...

The treatment of high-nitrogen complex wastewater in an efficient, economical, and environmentally friendly manner has attracted growing attention in recent years. However, slow reaction rates remain a significant obstacle to its broad application. This study investigated the addition of Mn@BC to enhance the low-temperature resistance of an anaerobic ammonia oxidation (anammox) process coupled with denitrification. The results demonstrated that under 17℃ conditions, the average nitrogen removal efficiency increased to 82% with the addition of Mn@BC, representing a 9% improvement compared to the addition of BC alone. Moreover, Mn@BC promoted the secretion of extracellular polymeric substances and diversified the microbial community structure.The incorporation of microalgae created a synergistic microalgal-bacterial system that maintained a phosphorus removal rate of 50% and reduced the reliance on external organic carbon, as confirmed by TOC analysis.The underlying intra- and extracellular metabolic pathways, formed by functional genes including mtrC, nirS/K, and c-Cyts, were elucidated using metagenomic sequencing. Therefore, the development of a high-efficiency nitrogen and phosphorus removal process capable of synchronizing microalgal-bacterial interactions, overcoming low-temperature inhibition, enhancing microbial synergy, and reducing carbon source dependency holds practical application value for treating high-nitrogen and low-temperature wastewater, while also providing theoretical support for constructing microalgal-bacterial synergistic systems to achieve efficient autotrophic nitrogen removal.