This chapter introduces the fundamental equipment used for aeration and mixing in water and wastewater treatment processes. Firstly, it provides an overview of aeration equipment, covering the main types and their specific applications. It then details safe operating procedures to ensure effective and reliable operation of aeration systems. Additionally, common faults and troubleshooting methods are included to help users address typical operational issues. Secondly, the chapter focuses on mixing equipment, beginning with an overview and followed by a description of submersible mixers commonly used in treatment processes. Safety operating procedures for mixing equipment are outlined, along with guidance on identifying and resolving common malfunctions.