Abstract:Currently, wastewater treatment plants predominantly use biological processes to degrade and remove pollutants. These processes consume energy, hinder resource recovery, and generate substantial greenhouse gas emissions. To address these issues, we developed a fully materialized process that couples the fluidized pellet bed (FPB) with the flow-electrode capacitive deionization (FCDI) system. This process separates pollutants from wastewater rather than degrading them, resulting in good effluent quality and reduced carbon emissions from the wastewater treatment process. It also allows the separated high concentration of pollutants to be used for carbon and nitrogen resource recovery. The results showed that the removal rates of chemical oxygen demand (COD) and total phosphorus (TP) in the FPB system were 70.71% and 84.64%, respectively. The removal rate of ammonia nitrogen (-N) in the FCDI system was 98.50%. The final effluent concentrations of COD, TP, and -N in the FPB-FCDI coupled process system were (13.43 ± 1.24), (0.16 ± 0.03), and (0.29 ± 0.08) mg/L, respectively, meeting Class Ⅳ surface water quality standards in China. Additionally, the FPB system effectively removed most non-dissolved or colloidal COD particles (0.45 - 6.00 μm). This reduced the potential impact of this COD on the downstream FCDI system. Consequently, this resulted in an enhancement of the nitrogen removal current efficiency in the FCDI system from 15.33% to 17.33% and a decrease in specific energy from 11.65 (kW·h)/kg to 10.31 (kW·h)/kg, demonstrating the full potential of the synergistic effects of the FPB-FCDI coupled process. In addition, the process exhibited a low-carbon characteristics, with the operational procedure capable of reducing greenhouse gas production and recovering potential resources, thereby facilitating the decarbonization. The energy utilization in the process was converted to carbon emissions, amounting to 0.42 kg CO2/m3, which was 53.83% of that in traditional biological treatment process. It is estimated that a further reduction of 0.19 kg CO2/m3 could be achieved by recovering electricity from the separated carbon sources of the FPB system using anaerobic digestion. The operating cost of the FPB-FCDI coupled process system was 0.42 RMB/m3, which was only one-quarter to one-half of the operating cost of the traditional domestic wastewater treatment process. Therefore, the study explores a novel low-carbon and high-efficiency wastewater treatment technology, providing a new approach for developing the next-generation of green, high-efficiency, and low-carbon wastewater treatment processes. Close-