This chapter covers the application of ANN in wastewater and freshwater treatment processes. Artificial intelligence (AI) is being used in water treatment to overcome the drawbacks of traditional approaches. AI has emerged as a potent tool for resolving real-world issues, and its applications in different fields have sparked a lot of interest. Its main focus is by lowering costs and optimizing chemical usage, thereby cut the operating costs of the water treatment process. © 2022 John Wiley & Sons, Inc.