Neonicotinoids, widely used pesticides, pose environmental risks due to their persistence in water sources. Conventional wastewater treatment plants struggle to eliminate these chemicals, making alternative methods essential. Constructed wetlands (CWs) offer a sustainable solution, utilizing plants, substrates, and microorganisms to remove pollutants. This study explores the use of iron-manganese (Fe/Mn) biochar in recirculating constructed wetlands (RCWs) to enhance neonicotinoid removal.

Fe/Mn biochar significantly improved the removal of imidacloprid (IMI) and acetamiprid (ACE), two common neonicotinoids, along with other pollutants like COD, NH4+-N, TN, and TP. However, the presence of IMI and ACE affected the elimination of nutrients from wastewater. Fe/Mn biochar promoted carbon, nitrogen, and phosphorus cycling in RCWs, aiding in the adsorption and biodegradation of these pesticides.

The study utilized metagenomics to analyze microbial communities, revealing that Fe/Mn biochar increased the abundance of biodegradation genes (BDGs), such as cytochrome P450, and identified potential bacterial hosts like Betaproteobacteria and Bacillus. These findings highlight how Fe/Mn biochar influences microbial dynamics, enhancing pesticide degradation.

Overall, Fe/Mn biochar proves to be a promising amendment for RCWs, effectively removing neonicotinoids and improving water quality. This research provides insights into optimizing constructed wetlands for treating pesticide-contaminated wastewater, offering a viable solution for mitigating the environmental impact of persistent pesticides.