Plant-derived carbon activates pyrite in tidal-flow constructed wetlands

Pyrite-associated autotrophic denitrification is a promising approach for simultaneous nitrogen and phosphorus removal from low C/N wastewater, yet its practical application is severely constrained by surface passivation that progressively diminishes reactivity. Here, we propose and validate a coupled strategy integrating tidal flow operation, a plant-based sustained-release carbon source (Ac-BDPs), and pyrite in constructed wetlands to address this bottleneck. Rather than relying on simple material mixing, this system is designed to achieve spatiotemporal coordination of chemical interfacial regeneration and microbial functional differentiation. Over 100 days of continuous operation under optimized conditions, the coupled system achieved average total nitrogen and total phosphorus removal efficiencies of 60.13 % and 90.52 %, respectively, significantly outperforming single-substrate controls. Mechanistic investigation revealed that dissolved organic matter released from Ac-BDPs reduced the pyrite interfacial charge transfer resistance by 46.3 % through synergistic ligand complexation and localized acidification, thereby alleviating surface passivation and sustaining the release of mineral-derived electrons and dissolved Fe(II). Concurrently, the tidal regime, in concert with Ac-BDPs amendment, reshaped the microbial community toward co-enrichment of heterotrophic denitrifiers (Thauera, 10.60 %) and autotrophic sulfur-oxidizing denitrifiers (Thiobacillus, 16.93 %), as evidenced by an expanded and highly interconnected co-occurrence network. This trophic differentiation, supported by interfacial renewal and periodic redox alternation, underpins the sustained nitrogen and phosphorus removal performance. Overall, this work demonstrates that integrating tidal forcing with complementary reactive substrates can establish a potential self-reinforcing loop of interfacial regulation and coordinated microbial participation, offering a transferable systems-level framework for enhancing the long-term stability of mineral-based water treatment technologies.