Carbon capture characteristics and mechanisms of municipal wastewater treatment using coagulation-enhanced HRCS system

This study optimized coagulation in HRCS systems for municipal wastewater treatment, investigating coagulant dosage effects on carbon capture and microbial communities. Real wastewater testing in coagulation-enhanced HRCS (CE-HRCS) systems further revealed carbon capture efficiency and microbial mechanisms, enhancing resource utilization. The results demonstrated that with a coagulant dosage of 20 mg/L, the combined proportion of Proteobacteria and Bacteroidetes , the pivotal bacteria for carbon capture, exceeded 90 %. This dosage achieved a maximum sludge extracellular polymeric substance (EPS) content of 150 mg/g VSS and a carbon capture efficiency of 83 %. Upon transitioning to real municipal wastewater, while the chemical oxygen demand (COD) removal rate slightly dipped to approximately 80 %, the carbon capture rate remained robust at 63 ± 2 %, down from 70 %. The EPS content stabilized at 138 ± 2 mg/g VSS, indicating a satisfactory carbon capture efficiency for practical municipal wastewater treatment. Moreover, the microbial population in the CE-HRCS system exhibited an increase in species richness and diversity. Although the proportion of Proteobacteria declined from 83 % to 62 %, the presence of Firmicutes and Bacteroidota increased, with carbon degradation-related functional bacteria continuing to dominate. This study offers valuable insights and new guidance for enhancing carbon capture from municipal wastewater using CE-HRCS technology. • The carbon capture efficiency enhanced to 83 % with a coagulant dosage of 20 mg/L. • Impact of different coagulant dosages on microbial community structure was studied. • The response relationship of EPS within the system was analyzed. • Microbial mechanisms of the efficient carbon capture of the system were revealed.