A Hybrid-Energy Harvesting System with Wastewater Treatment Using EBR, RED and CapMix

Abstract

Salinity gradient power (SGP) or Salinity gradient energy (SGE) is a renewable energy source that has its origin from the mixing of waters of varying salinity. In this work, a novel hybrid system consisting of Capacitive Mixing (CapMix), Reverse Electrodialysis (RED), and Electroactive Biofilm Reactors (EBR) in a system that can generate energy from industrial effluent and treat wastewater simultaneously is explored. The hybrid system utilizes the synergistic advantages offered by CapMix and RED to enhance energy production and the application of EBR to prevent membrane fouling in RED to increase overall efficiency and ensure environmental responsibility. Another significant contribution of this work is the development of composite electrodes for the CapMix mechanism with 3D Porous Carbon, Chemically Activated Graphene Oxide, a chitosan–gelatin binder, and a Zwitterionic Polymer Coating to minimize fouling. Research on three-way hybrid systems and their applications in industrial effluent is limited despite the inherent potential of SGE technologies. This work addresses this gap by demonstrating the feasibility and advantages of the proposed system in clean energy generation and wastewater treatment, thus ensuring sustainable industrial operations and freshwater resource conservation.

Introduction

The increasing global demand for clean energy and effective wastewater treatment has driven innovation in technologies that address both simultaneously. Salinity Gradient Energy (SGE), based on Gibbs free energy released from mixing waters of different salinities (e.g., river and seawater or industrial effluents), offers significant renewable energy potential. Key technologies in this space include:

• Pressure Retarded Osmosis (PRO) – high power density, limited by membrane fouling.

• Reverse Electrodialysis (RED) – moderate power density, suffers from membrane fouling.

• Capacitive Mixing (CapMix) – low power density but simple and membrane-free.

Each has strengths and weaknesses, with fouling and low efficiency being major barriers.

Proposed Innovation: Three-Way Hybrid System

A novel hybrid system is proposed that integrates:

• RED (ionic gradient energy harvesting),

• CapMix (capacitive energy extraction),

• Electroactive Biofilm Reactors (EBRs) (wastewater treatment and fouling mitigation).

This system:

• Uses industrial effluents, rich in salts and organic matter, as both a source of energy and pollution.

• Leverages advanced composite electrodes (3D carbon, graphene oxide, zwitterionic coatings) for high conductivity, surface area, and anti-fouling performance.

• Applies biofilms in EBRs to break down organic pollutants and reduce membrane fouling in RED.

Key Advantages

• Dual Functionality: Simultaneous clean energy generation and wastewater treatment.

• Fouling Mitigation: Biofilms and zwitterionic coatings reduce maintenance and extend system lifespan.

• Sustainability: Promotes industrial waste recycling and clean energy goals.

Research Objectives

1. Design an efficient modular hybrid system integrating RED, CapMix, and EBR.

2. Implement anti-fouling technologies like piezoelectric vibration and zwitterionic coatings.

3. Develop high-performance interdigitated electrode stacks with enhanced properties.

4. Bridge the research gap in hybrid SGE applications for industrial wastewater.

Technological Context & Literature

• RED: Proven, membrane-based energy recovery; needs better fouling-resistant membranes.

• CapMix: Emerging, low-cost, membrane-free option; needs power density improvement.

• EBRs: Advanced bioelectrochemical systems that both treat wastewater and support energy generation.

• Hybrid systems: Offer improved energy recovery and treatment efficiency when integrating technologies with complementary strengths.

Conclusion

In this paper, we have mentioned some different innovations applied in utilizing salinity gradient energy. To begin with, the whole system performs two purposes-wastewater treatment and power generation. The system incorporates biological elements (i.e, the biofilm of microorganisms of the EBR) and electrochemical systems in an attempt to miniaturize and make the process efficient. EBR, for example, is an innovation that reduces fouling to a much greater degree than the conventional MFCs. The electrodes used throughout all 3 components of the system are also built with a particular set of materials. Specifically, the use of biochar, graphene, and zwitterionic coating, as a whole, is key to system efficiency enhancement. In the RED stack, the use of zwitterionic coating and piezoelectric actuators significantly prevents membrane fouling. Therefore, anti-fouling measures in RED membranes significantly reduce pollutants. Our device uses RED and CapMix in order to harness the maximum energy that is available. Anti-fouling technology is used in RED, but CapMix does not suffer from this issue because it harvests energy without the need for membranes. It is thus able to harness the remaining salinity gradient to create energy without creating more issues. At present, this model has been developed for producing clean energy from a comparatively smaller channel of wastewater. After being showcased in real-world conditions, the system can then be scaled up to dams- which contain much higher water flow. Consequently, it would be capable of producing more energy from fewer acres of land. Overall, this integrated design provides us with a vision of a future that is full of hope where energy is being harnessed efficiently and in a sustainable manner.

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Copyright

Copyright © 2025 Abhinav Chandna, Aarna Malhotra, Aleya Chatterjee. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.