Self-Regulating pH Pyrite-Construction waste Biofilter: Denitrification Performance, Metabolic Pathways, and Clogging Alleviation

Waste-based denitrification filters face challenges like alkalinity accumulation, low efficiency, and clogging. This study proposes a novel denitrification filter using construction waste and pyrite (WPDF) to address these issues. WPDF's performance, safety, and mechanisms were evaluated by measuring effluent, filler characteristics and metagenomics. Results demonstrated a high total nitrogen removal load (88.65 g N m^-3d^-1) with minimal biofilm (13 %) and filler accumulation (39 %), effectively mitigating clogging. Phosphorus removal relied on chemical precipitation in construction waste. WPDF was pH self-regulating and promoted the formation and release of fulvic acid. Pyrite promotes bio-metabolism, making WPDF enriched in energy metabolism (6 %) and transporter capacity (6 %). Functional prediction indicated that WPDF was more abundant in genes related to denitrification, glycolysis, and electron transport, which promoted the heterotrophic denitrification process. This study provides a novel, efficient, and eco-friendly possible solution for wastewater and offers new insights into the molecular mechanisms of carbon and nitrogen metabolism.