This chapter covers the conventional technologies, including thermal, membrane, solar evaporation, and freeze-thaw desalination processes. It also gives an overview of how gas hydrate-based desalination can help in treating wastewater. Each technology is described in detail, showing how the process works and reporting some data on the state of development. Each technique is discussed in detail, with diagrams demonstrating how the process works. This chapter also discusses the benefits and drawbacks of each of these strategies, as well as the economic considerations involved. © 2022 John Wiley & Sons, Inc.