Synergizing MBR and MCDI systems as a sustainable solution for decentralized wastewater reclamation and reuse

Decentralized wastewater reclamation and reuse systems have drawn much attention due to their capability for reducing the energy demand for water conveyance and reclaiming wastewater for local re-use. While membrane bioreactor (MBR) stands as a mature technology offering comprehensive solid and liquid separation, membrane capacitive deionization (MCDI) presents a promising avenue for ion separation. Unfortunately, MCDI has seldom been incorporated into decentralized wastewater reclamation and reuse systems. This study aims to exemplify the design and the operation of the synergistic integration of MBR and MCDI system with a practical capacity of 1 m3 d− 1, showcasing its efficacy in reclaiming and reusing water at regional level. The integrated system demonstrated significant high removal of total organic carbon (from 97 to 2 mg L− 1) and chemical oxygen demand (COD, from 218 to < 3 mg L− 1). Meantime, nearly complete transformation (approximately 91%) of NH3 to NO3− within the MBR effluent was observed with a hydraulic retention time of 4.3–4.8 h and a food-to-microorganism of 0.15–0.20 kg COD kg− 1 MLSS d− 1 which can be further removed through the MCDI system (> 92% TN removal). A significant milestone of MCDI unit was reached with the remarkable removal efficiency of total ions (93%) and water recovery (80%) using a stop-flow regeneration approach coupled with an optimized voltage of 2.0 V. The MCDI unit not only proved its high stability but also featured low energy consumption (0.44 kWh m− 3). Overall, synergizing MBR and MCDI systems emerges as a sustainable and effective solution for decentralized wastewater reclamation and reuse, contributing to a more environmentally friendly and resource-efficient water management paradigm.