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• The maximum treatment capacity of 1167.44 g is achieved in Mode 1 systems. • Optimization of operating conditions enhances energy efficiency and reduces costs. • Systems in Mode 2 exhibit higher energy efficiency but a lower COD removal value. • Switching modes maximize energy utilization across different application scenarios. A multi-stage reverse electrodialysis reactor (MSREDR) wastewater treatment system with an independent strategy is researched theoretically in this paper. The influences of operating conditions on the system performance and levelized costs are explored. Results illustrate that reducing the number of membrane pairs not only enhances the system performance but also decreases the levelized cost of wastewater treatment. A high concentration of concentrated solution facilitates enhancing the total COD removal value and reducing the levelized cost, but it adversely affects the energy conversion efficiency of the system. The optimal total COD removal value and energy efficiency are respectively 1164.77 g and 3.58 % under the given conditions. However, when the wastewater discharge rate from the plant is lower than the maximum treatment capacity, it transitions from a wastewater treatment mode to a combined power generation and wastewater treatment mode. Compared to the system operating in the wastewater treatment mode, the system operating in the combined power generation and wastewater treatment mode exhibits higher effective energy and energy efficiency but a lower COD removal value. This research successfully achieves the flexible adjustment of operating modes based on real-world applications, thereby maximizing energy efficiency and establishing a theoretical foundation for practical implementations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Feasibility of using organic wastewater as renewable energy source is verified. • ＞99% COD, TOC removal rate in the experimental platform. • Up to 78.75% of the energy recovery efficiency of the SCWO system. The degradation of high concentration organic wastewater and the recovery of energy using supercritical water oxidation (SCWO) technology have the potential to become viable in the future. High concentration organic wastewater contains a significant amount of energy. This paper focuses on utilizing high concentrated wastewater as a renewable energy source, from an energy system perspective, an experimental rig was designed to determine the optimal working conditions. The experiments were conducted with an oxidation coefficient of 1.1, a flow rate of high concentration organic wastewater of 9 ml/min, a heating temperature of 400 °C, and a reaction pressure of 25 MPa. Under these conditions, the COD and TOC removal rates of the high concentration organic wastewater were found to be 99.383 % and 99.876 % respectively. Additionally, the phenomenon of "Abnormalities in pressure sensitivity" observed during high concentration organic wastewater the experiment was further explained through additional experiments. Finally, by comparing the experimental energy recovery with the simulation results, an energy recovery efficiency of 78.95 % was achieved. The feasibility of the simulated energy recovery in practice was verified, confirming the potential to convert the previous energy-consuming wastewater treatment process into a productive one. This study provides a theoretical and experimental foundation for further related research. [ABSTRACT FROM AUTHOR]