Solar-Powered Electrochemical Processes for Sustainable Wastewater Treatment and Green Hydrogen Production: A Review

The development of cities as well as industries starts generating more and more domestic and industrial effluents which are rich in organic matter, total dissolved solids (TDS) and heavy metals. Effluents of such kinds effect aquatic ecosystems adversely and present both technical and economic challenges to conventional treatment technologies. In this respect combination processes of electrochemistry with renewable energies, and more particularly photovoltaic solar energy, seems a promising means of developing efficient and sustainable wastewater treatment technologies. Electrocoagulation uses sacrificial aluminum electrodes to generate coagulants in situ. This helps in reducing COD, TDS, and turbidity. On the other hand, electrooxidation using DSA boron-doped diamond electrodes treats the waste by oxidizing resistant organic pollutants. Furthermore, it identifies the usability and utility benefits of such technologies, such as for designing energy-autonomous wastewater treatment facilities, minimizing dependence on the electrical grid, and reducing carbon prints. Furthermore, the systems have the potential to provide operational resilience and environmental sustainability as an added advantage of pollutant removal and energy recovery. In spite of these encouraging results, a number of technical and economic limitations still exist, including effluent variability, complexity of systems, and high capital investment. These limitations are reviewed in this chapter and opportunities for continued research are outlined, such as process optimization, increased hydrogen production, modular reactor design, and deployment of decentralized treatment systems. In brief, synergy between solar power and electrochemical processes is a strategic path towards having sustainable, energy-scarce, and environmentally friendly wastewater treatment systems.