Arbuscular mycorrhizal fungal inoculation as a potential approach for enhancing pollutant removal from tailwater in Acorus calamus constructed wetlands.

The residual organic matter, nitrogen, phosphorus, and heavy metals (HMs) in the effluent from wastewater treatment plants pose persistent risks to the ecological environment. To enhance advanced treatment of synthetic tailwater, this study used CWs based on the symbiosis of Acorus calamus and arbuscular mycorrhizal fungi (AMF) and investigated its pollutant removal efficiency and underlying mechanisms. The results showed that AMF inoculation significantly increased the removal rates of organic matter and total nitrogen by 11.35% and 16.62%, respectively, while TP removal showed a non-significant increasing trend (7.65%), respectively; reduced N₂O flux and peak emissions by 39.34% and 21.96%. Compared with the control group, AMF symbiotic treatment showed more positive changes: AMF-plant symbiosis significantly increased plant biomass and significantly enhanced plant HM content and accumulation (Cr, Ni, Pb, and Zn). Meanwhile, changes in microbial diversity and the relative abundance of microbial communities related to nitrogen and phosphorus cycling indirectly enhanced the removal of organic matter, nitrogen, and phosphorus in CWs. In addition, changes in the abundance of functional genes related to carbon metabolism and nitrogen transformation/reduction were consistent with organic matter and nitrogen removal and reduced N₂O/TN emissions. In summary, this study proposes that the AMF-plant symbiosis may coordinately enhance the advanced treatment performance of CWs for synthetic tailwater through plant-microbial community-functional gene interactions, thereby providing new insights for the application of plant-microbe symbiotic technology in advanced tailwater treatment.