Porous polymers embedded with iron carbon enhanced densified activated sludge formation and wastewater treatment

Municipal wastewater treatment plants in China face significant challenges in effectively removing pollutants from low-strength wastewater with a low carbon-to-nitrogen (COD/N) ratio. This study proposes a novel approach incorporating porous polymers embedded with iron-carbon (PP-IC) into an activated sludge system to enhance treatment. The PP-IC accelerated the formation of densified activated sludge (DAS), characterized by small particle sizes (<200 μm), excellent settleability (sludge volume index: 61 mL/g), and improved pollutant removal efficiency, with total nitrogen and total phosphorus removal rates increasing by 14.4 % and 57.4 %, respectively. DAS formation was achieved within 7 days and stabilized after 42 days. The enrichment of microorganisms, including unclassified_f_Caldilineaceae, Dechloromonas, and Candidatus Accumulibacter, further enhanced pollutant removal. Additionally, Fe²⁺, Fe³⁺ and hydroxyl radical (·OH) produced by iron-carbon micro-electrolysis supported DAS formation. Microbial interactions with the iron shavings sustained the long-term stability of the micro-electrolysis process. This synergistic mechanism significantly improved pollutant removal in wastewater treatment.