A novel carbon-negative side-stream MBMBR process for municipal wastewater reclamation driven by biopolymer and...

With the rapid evolution of global climate change and resource shortages, there is a growing need for technological innovation to achieve energy and carbon-neutral wastewater reclamation. In this study, a high-rate side-stream moving bed membrane bioreactor (MBMBR) process was used for municipal wastewater reclamation via COD capture for biopolymer harvesting and nutrient recovery. The results revealed excellent COD capture ability (organic conversion loading of 2.64 g COD/L/d) and a high nitrogen retention rate (92.7 %) in the MBMBR process, with a short hydraulic retention time of 1.0 h. Moreover, the yields of alginate-like exopolymers recovered from the MBMBR process ranged from 213.0 to 272.9 mg/g VSS, which was significantly higher than the yields from conventional activated sludge (CAS) (90-190 mg/g VSS). Additionally, the energy demands, net profits, and carbon emissions of the MBMBR process were further evaluated for comparison with the CAS-MBR process. The energy demands and net profit evaluations for the MBMBR process were estimated to be 0.510 kWh/m³ and 0.025 USD/m³, respectively, compared to 0.647 kWh/m³ and -0.077 USD/m³ for the CAS-MBR process. Furthermore, it was demonstrated that the COD capture for resource recovery in the MBMBR process could offset approximately 837.45 g CO₂e/m³, which was 9.50 times than that in the CAS-MBR process. With this significant portion of carbon offsetting, the total carbon emissions in the MBMBR process (-234.54 g CO₂e/m³) were significantly lower than in the CAS-MBR process (900.90 g CO₂e/m³). This indicates that value-based resource conversion and recovery from wastewater could be a game-changer in the design of next-generation wastewater treatment processes.