Deciphering effect of complex organics on Anammox-sulfide autotrophic denitrification coupling system for landfill leachate treatment.

The inhibitory effects of complex organics on Anammox-sulfide autotrophic denitrification (SAD) coupled systems are not well understood in full-strength leachate conditions. This research examines the removal of carbon, nitrogen, and sulfur, alongside microbial symbiosis and metabolic alterations, within an Anammox-SAD system that processes raw landfill leachate. The system attained a total nitrogen removal rate of 98.54 ± 0.42 %, with contributions of 89.47 % from Anammox and 10.53 % from SAD. The system attained a total nitrogen removal rate of 98.54 ± 0.42 %, with contributions of 89.47 % from Anammox and 10.53 % from SAD. GC × GC-TOFMS analysis indicated removal rates of 72.33 %, 51.05 %, and 53.81 % for small-, medium-, and large-molecular-weight organics, respectively, by the Anammox system, thereby reducing stress on SAD. Metagenomics studies revealed that low-molecular-weight organics promoted DNRA, partial denitrification, and Anammox through enhancing electron transfer and functional gene expression. The role of Anammox bacteria in carbon fixation decreased, whereas sulfur metabolism in SAD became increasingly dependent on Sulfurimonas-mediated Sox pathways, indicating metabolic adaptation in response to organic stress and competition between autotrophs and heterotrophs. This study provides novel insights into the application of Anammox-SAD coupled processes for landfill leachate treatment.